Weighing In: Discovering the Ploidy of Hybrid Large Leaf Elepidote Rhododendrons

Weighing In (Published in RHS Rhododendrons, Camellias, and Magnolias Yearbook 2012)

When we mention the word ploidy most gardeners' eyes glaze over. What does ploidy have to do with their beautiful garden specimens of rhododendrons?

Yet if we mention 'Cynthia', 'Gomer Waterer', 'Grace Seabrook', 'Horizon Monarch', 'Marinus Koster', 'Pink Pearl', 'Phyllis Korn', 'Point Defiance', 'Taurus', or 'Trude Webster', gardeners quickly add that these are among their favorite rhododendrons or high on their wish list. Yes, these Rhododendrons display "something different" and "highly desirable."

As dozens more Rhododendrons with larger than normal ploidy levels are revealed below, we hope gardeners see the connection with characteristics of thickness in the leaf and firmness in flower substance. Indeed, remarkable vigor and substance overall, coupled with outstanding floral performance at a young age, starts to make sense. Even gardeners, who do not want to talk about ploidy, love talking about polyploids.

We are not geneticists. We do have science backgrounds with a passion for knowledge. Our ploidy journey began as simple curiosity combined with a willingness to coordinate with others, scour the Rhododendron literature and the web, and do some field work leading to more discoveries than we ever imagined.

First, when we refer to ploidy we mean the size of the genetic material of the plant. Genetic material is, in seed bearing plants, the genetic material found in the nucleus of the cell packed into structures called chromosomes.

There are 2 different techniques used to determine how much genetic material is in a cell and therefore, an estimate of the number of chromosomes that are present in the cell. One can count the ways or weigh the counts.

Count the ways: The classic way to determine the number of chromosomes in a plant is to visualize the chromosomes with stain when they are actively growing, as in a root tip, and then count the different pairs under the microscope. Reports are that this is very tedious, more so in rhododendrons, prone to error, and even eager graduate students are reluctant to cooperate. There are very few studies, mostly older, and even less duplication of results.

Weigh the counts: With the technique of flow cytometry it is possible to weigh the genetic material by taking healthy plant tissue and measuring the weight of the genetic material. This technique is much less time consuming and therefore easier to verify by duplicating results. Flow cytometry was developed to detect mutations in tumors and cancer cells. If the cells are normal and growing there would be a small number of cells with double the weight of their chromosomes as they would be in the phase prior to division. Any cells with less than or more than that weight would be an indication of mutations of the amount of genetic material in the cell (i.e. cancer). This valuable technique can also be used to detect the normal weight of genetic material in different species and hybrids of rhododendrons.

Polyploidy: Beginning with 1, 2, 3, 4, 5

In most plant cells, i.e. leaves, stems, roots and some parts of the flower; the chromosomes are paired with a matching chromosome to form the diploid state. We say most cells because when it comes time to reproduce, the unfertilized seed and the pollen are formed by the splinting apart of the paired chromosomes forming a nucleus with a single set of chromosomes; the unpaired or haploid state. And just to make things complicated true seeds have extra diploid tissue from the seed parent which merges with a haploid pollen nucleus to form the endosperm of a seed. The fertilized endosperm therefore has 3 sets of chromosome (2 from the seed mother and one from the pollen father) and is triploid. This extra genetic material nourishes the germinating seedling.

Most Rhododendrons get one set of chromosomes, denoted as 1x, from each parent (female and male) resulting in two sets of chromosomes, are commonly referred to as diploids, and denoted as 2x (1x + 1x = 2x). However some Rhododendrons have four sets of chromosomes, are commonly referred to as tetraploids, and denoted as 4x (2x + 2x = 4x). Triploids have three sets of chromosomes and are denoted 3x. Pentaploids have five sets of chromosomes and are denoted 5x. Rhododendrons having more than two sets of chromosomes are referred to as polyploids. [reference]

Although most Rhododendron species are diploids, tetraploid Rhododendron species exist [reference]. Individual triploid Rhododendrons, appearing to be hybrids, sometimes occur naturally where diploid and tetraploid species of Rhododendron are co-located. [reference]

Discovering: the Journey

In the fall of 1989, our Rhododendron polyploidy journey unknowingly started when we overheard at a local Rhododendron meeting a statement Frank Mossman wrote in 1972 concerning his hybridization efforts with Rhododendron occidentale: [reference]

"We have found that Rhododendron occidentale will cross with many other rhododendrons or azaleas if Rhododendron occidentale is the seed parent, but Rhododendron occidentale as a pollen parent produces few seed."

We wondered why.

In the fall of 2011, we uncovered that in 1972 Harold Greer wrote the following concerning his hybridization with 'Countess of Derby' to produce 'Trude Webster': [reference]

"If you are one of those who feels that there could be nothing outstanding produced in a pink rhododendron I would have been the first to agree with you. That was until I saw the first bud unfold on the original seedling of R. 'Countess of Derby' selfed."

Both Mossman and Greer had encountered the wonder accompanying the many puzzles presented by polyploid Rhododendrons, so we were in good company.

Starting in the early 1990's, we unknowingly crossed deciduous azalea involving different ploidy levels leading in 2010 to collecting samples of diploid, triploid, and tetraploid Rhododendrons for ploidy testing at the University of Coimbra in Portugal. Each step on this pathway revealed more about the wonderful world of ploidy in our own Rhododendron garden.

Below is a summary of what we discovered, often based on the research, observations, and documentation of many others, about the ploidy of hybrid large leaf elepidote Rhododendrons and the people encountered on our slow but wondrous journey.


Figure 1: Generational Breeding of Polyploid Hybrid Elepidotes

The ploidy of named hybrid large leaf elepidote Rhododendrons as determined using flow cytometry by

Dr. João Loureiro, Dr. Silvia Castro, José Cerca Oliveira, and Mariana Castro
Plant Ecology and Evolution Group,
Centre for Functional Ecology,
Department of Life Sciences,
Faculty of Science and Technology,
University of Coimbra, Portugal

unless otherwise indicated.

Summary of Ploidy

2x Diploids

1000 Butterflies
Alice
Anna (Lem, 1952) U
Betty Hume
Bibiani
Cheyenne *
Colonel Coen
Countess of Athlone
Diane
Duke Of York
Elegans
Everlasting *
Fantastica *
Furnivall's Daughter
Gillii
Gill's Triumph
Goldflimmer *
Goldsworth Orange #
Graf Zeppelin (van Nes, 1934) P
Horizon Lakeside
Hotei
Hurricane (Whitney, 1960) P
Isabel Pierce
Janet Blair *
J.G. Millais (Waterer, 1915) P
Jingle Bells #
Kathy Van Veen
Kristian's Pink
Kupferberg #
Lady Bligh
Lady de Rothchild
Lady Eleanor Cathcart
Lavendelmilch
Lem's Cameo
Loderi Venus
Madame Carvalho
Maxicat *
maximum Kalamity
Mindy’s Love
Mother of Pearl (sport, 1925) P
Mrs A. T. De la Mare
Mrs Lindsay Smith
Mrs. Furnival
Nancy Evans
Naselle
Norman Gill
Nova Zembla *
Olin O. Dobbs
Orange Leopard (Brack, 1988) P S
Peach Charm
Peach Recital (Barlup, 1996) P
Phipps Yellow
Pink Prelude
Polar Bear *
Puget Sound *
Red Olympia
Rendezvous (Hachmann, 1968) P S
Stony Brook (Brack, 1988) P S
Summer Peach (Barlup, 1988) P
Summer Wind (Barlup, 1996) P
The Honourable Jean Marie de Montague (van Nes, 1901) U
Viscy #
Voluptuous
Vulcan *
Vulcan’s Flame *
White Pearl syn Halopeanum
Wild Affair

3x Triploids

Anita Gehnrich (Gehnrich) UM
Anna Rose Whitney (Van Veen, 1954) F NM
August Lamken (Hobbie, 1942)
Beauty of Littleworth (Mangles, 1884)
Betty Wormald (Koster, 1907) F
Broughtonii (Broughton, 1840) F
Cotton Candy (Henny and Wennekamp, 1958) F UM
Cynthia (Standish and Noble, 1856) F
Dame Nellie Melba (Loder, 1926)
Ebony Pearl (sport, 1966)
Django (Hachmann 1985)
El Camino (Whitney, 1976) NM
Gartendirektor Rieger (Hobbie, 1947)
Gomer Waterer (Waterer, 1900) F DM
Grace Seabrook (Seabrook, 1965) UM
Hallelujah (Greer, 1958)
Hank's Folly (Schannen) NM
Julia Caroline (Brockenbrough, 1990) NM
Lady of Spain (Lofthouse, 1966) NM
Lucky Strike (Van Veen, 1958) NM
Lydia (Greer, 1963) F NM
Markeeta's Flame (Markeeta, 1960) UM
Markeeta's Prize (Markeeta, 1970) UM
Opal Thornton (Thornton) NM
Pearce's American Beauty (Pearce, 1930) F
Phyllis Korn (Korn, 1969) F DM
Pink Pearl (Waterer, 1892) F DM
Platinum Pearl (Greer, 1983) F NM
Rothenburg (von Martin, 1944)
Rwain (Colombel, 1993) F NM
Solidarity (Schannen, 1969) F UM
Steredenn (Colombel) NM
Sugar Pink (Greer, 1960) NM
Super Dog (Bones) NM
Taurus (Mossman, 1962) F UM
Topsvoort Pearl (sport, 1935)
Val d'Aulnay (Croux and Fils, 1984) F
Van (Van Veen, 1930) NM

4x Tetraploids

Antoon van Welie (Endtz, 1930) 3X2
Brigg's Red Star (Briggs) T
Cherry Cheesecake (Briggs) T *
Countess of Derby (White, 1913) 3X3
diaprepes Gargantua (Stevenson, 1923)
Doreen Gale (Sanders) 4X4
Gentle Giant (Sanders, 1992) 4X3
Gorgeous George (Sanders) 4X4
Grand Slam (Greer, 1982) 4X3
Horizon Jubilee (Brockenbrough) *
Horizon Monarch (Brockenbrough, 1981) 2X4
Le Fouesnantais (Colombel, 1997) 4XQ
Legend (Barlup) 4X4
Lem's Monarch syn Pink Walloper (Lem, 1965) 2X4
L'Engin (de la Sablière) 4X2
Marinus Koster (Koster, 1937)
Point Defiance (Lem, 1970) 2X4
Summer Joy (Kehr) T
Super Nova (Briggs) T *
Trude Webster (Greer, 1960) 4x4
Very Berry (Greer, 1988) 4X2

F indicates a fertile triploid.
T indicates a chemically induced tetraploid.
P indicates a diploid with a polyploid ancestor.
S indicates a diploid with a tetraploid parent.
U indicates a diploid with a tendency to produce unreduced gametes.
DM indicates a triploid resulting from a triploid parent.
NM indicates a triploid resulting from a tetraploid parent.
UM indicates a triploid resulting from 2 diploid parents.
2X4 or 4X2 indicates a tetraploid resulting from a diploid and a tetraploid parent.
3X2 indicates a tetraploid resulting from a triploid and a diploid parent.
3X3 indicates a tetraploid resulting from 2 triploids parents.
4X4 indicates a tetraploid resulting from 2 tetraploid parents.
4X3 indicates a tetraploid resulting from a tetraploid and a triploid parent.
4XQ indicates a tetraploid resulting from a tetraploid parent.
* indicates flow cytometry ploidy testing was done by research team lead by Dr. Ranney.
# indicates flow cytometry ploidy testing was done by Tom Eeckhaut.
(,) indicates the name of the hybridizer and date of cross.

Noteworthy is the named form diaprepes 'Gargantua'. There is no evidence that the species diaprepes is tetraploid. ONLY the named form 'Gargantua' has tested as tetraploid. To date, no large leaf elepidote species as a population has tested as tetraploid, but this could change.

For a brief history on how a few of these named polyploid elepidotes evolved read It is a Beautiful Spring Day in 1913 so What Do You Do? See figure 1 above.

Historical evidence indicates that by 1910 the triploids 'Betty Wormald', 'Beauty of Littleworth', 'Broughtonii', 'Cynthia', 'Gomer Waterer', 'Pink Pearl' would have been on most peoples' lists of best large leaf Rhododendrons.

In 1958, George Grace's list of best large leaf Rhododendrons included all but one of these triploids plus the tetraploids 'Countess of Derby' and 'Marinus Koster'.

In 2008, the Siuslaw Chapter of American Rhododendron Society included on their list of best large leaf Rhododendrons the triploids 'Cynthia', 'Dame Nellie Melba', 'Grace Seabrook', and 'Taurus', and the tetraploids 'Grand Slam', 'Lem's Monarch', 'Horizon Monarch', 'Point Defiance', and 'Very Berry'.

By 2011, examination of rhododendrons of the year, proven performers, [2], [3], [4], [5], [6], [10], [11], Award of Garden Merit and best in show trusses adds to the "bests" mentioned above the triploids 'Anita Gehnrich', 'Anna Rose Whitney', 'Cotton Candy', 'Ebony Pearl', 'Gartendirektor Rieger', 'Hallelujah', 'Markeeta’s Prize', 'Platinum Pearl', 'Solidarity', and 'Super Dog' and the tetraploids 'Gentle Giant' and 'Trude Webster'.

'Pink Pearl' won the first Award of Merit in 1897 and was selected Rhododendron of the Year in 2006 by the Southwestern Chapter of the American Rhododendron Society. In 1950, a large 'Cynthia', bred in 1858, was the first Rhododendron planted in the Crystal Springs Rhododendron Garden. 'Trude Webster' won American Rhododendron Society's first Superior Plant Award in 1971 and is still found on lists of proven performers for the west coast. 'Broughtonii', bred in 1840, is still considered to be among the best warm weather Rhododendrons according to Burke who gardens in Australia.

In other words, over twenty-five of the fifty or so confirmed polyploid large leaf Rhododendrons have appeared on lists of the best Rhododendrons and once these polyploids appear on such lists they tend to make future such "best" lists.

The following hybridizers have worked with or produced polyploid elepidotes hybrids:

Barlup
Bones
Boulter
Bovees
Brack
Briggs
Brockenbrough
Broughton
Bruns
Colombel
Croux and Fils
de la Sablière
Drake
Elliott
Endtz
Evans
Farwell
Felix and Dijkhuis
Fennichia
Fujioka
Gill
Greer
Gehnrich
Hachmann
Hall
Hartman
Heinje
Henny and Wennekamp
Hobbie
Horlick
Horsley
Johnson
Kavka
Kehr
Korn
Koster
Larson
Laxdall
Lem
Loder
Lofthouse
Mangles
Markeeta
McCullough
Moynier
Mossman
Murcott
Naylor
Ostler
Patterson
Pearce
Perkins
Rabideau
Ragans
Reuthe
Sanders
Schannen
Seabrook
Shapiro
Smith
Standish and Noble
Stead
Stevenson
Stockman
Thacker
Thornton
van Nes
Van Veen
Vinson
von Martin
Walton
Waterer
White
Whitney
Wilson
Winberg and Smith
Woodard

Noteworthy is that more hybridizers have worked with confirmed large leaf elepidote polyploids than there are such confirmed polyploids. More importantly, some of the hybridizers on this list are best known for the polyploid elepidotes they have created. In fact, in a few instances polyploid elepidotes have been named in honor of a wife, a mother, or a grandparent.

By the way, Mossman working with the diploid deciduous azalea species Rhododendron occidentale discovered what Barlup later discovered working with hybrid elepidotes: diploids are much more likely to accept pollen from tetraploids than tetraploids are to accept pollen from diploids. Our Rules of Engagement addresses this topic in detail.

Jim Barlup wrote the following about using polyploid large leaf elepidotes as parents: [reference]

"I continue to test the pollen and plants which I doubt for 3 or 4 years to determine their fertility or sterility. If you cross a diploid with tetraploid pollen you can achieve beautiful seedpods but their germination is very difficult. 3% seed germination for 'Point Defiance'. Obtained are both diploid or tetraploid offspring."

Breeding with polyploid large leaf elepidotes is not an easy task which explains why so few polyploids have been created to date despite so many hybridizers having attempted to use them as parents.

Ron Naylor wrote the following about his best plant, 'Francis Augustus Storey', from a cross involving 'Point Defiance': [reference]

"'Francis Augustus Storey' - Best of grex of four plants from weak germination. One died in 2000 and another in 2001."

Dick Murcott wrote the following about the plant he calls 'TT116': [reference]

"TT116 – [('Jean Marie' x R. yakushimanum) x 'Grand Slam']. Only one seed from this cross germinated. Looks like a tetraploid. Pink. Looks like 'Trude Webster' but is definitely a seedling."

Barlup, Murcott, and Naylor each encountered both the wonder and puzzles presented by polyploid Rhododendrons.

We have discovered for deciduous azaleas that seed produced from tetraploid X tetraploid normally has high rates of germination but germination from diploid X tetraploid crosses varies greatly but is normally low.

To read about Frank Abbott's encounter with the wonders of working with deciduous azaleas of different ploidy levels see Frank Abbott's Village of Azaleas or 'Margaret Abbott' is a Tetraploid.

The following people and organizations donated samples for this research:

John Abbott,
Vivian Abney of East Fork Nursery,
Living Collection of Arnold Arboretum,
Natural Collection of Audra State Park,
Living Collection of Bartlett Arboretum,
Jim Barlup,
Bruce Clyburn,
Jane Brooks,
Joe Bruso,
Werner Brack,
Ned Brockenbrough,
Natural Collection of Canobie Lake, NH,
Dick Cavender,
Living Collection of Connecticut College Arboretum,
Marc Colombel,
Mike Creel,
Hans Eiberg,
Al Fitzburg,
Robert Fox,
Harold Greer of Greer Gardens,
George Hibben,
Living Collection of Highstead Arboretum,
Don Hyatt,
Lindy Johnson of Appalachian Native Plants,
Richard Jaynes of Broken Arrow Nursery,
Doug Jolley,
Fred Knippel,
Living Collection of Longwood Gardens,
Wayne Mezitt of Weston Nurseries
Ron Miller,
Dick Murcott,
Michael Medeiros of Planeview Nursery, Portsmouth, RI
Peter Norris,
Mike O'Hara,
John and Sally Perkins,
Ron Rabideau of RareFind Nursery,
Ellie Sather of Whitney Gardens,
Natural Collection of Stoddard Blog, NH,
Kristian Theqvist,
Patrick Thompson of Auburn University
John Thornton,
Hendrik Van Oostand of Azaleatuin,
Kathy Van Veen of Van Veen Nursery

We wish to thank everyone who donated samples for this research.

Named Elepidotes Suspected of being Polyploid:

Adriaan Koster
Aggie
Aibette
Alibaby
Annie E. Endtz
Arden Primrose
Ariel Sherman
Aristide Briand
Arnold Piper *
Arthur Ostler
Babar
Bellevue
Bernard Crisp
Bernard Shaw
Boskoop Concorde
Bruns Sirius
Canadian Beauty *
Cara Meg
Caruso
Castanets
Charis
Courtenay Duke
Dagmar
Denali
Diane Marie
Diane Titcomb
Direktor Siebert
Doctor A. Blok
Doctor Arnold W. Endtz
Doctor H.C. Dresselhuys
Don Juan
Donald Waterer
Doris Nolan
Double Drake
Dr. V.H. Rutgers
Edward Cornelius
Elizabeth Titcomb
Ester Grace
Eureka Maid
Fiona Wilson
Forever Violet
Fragrant Sensation *
Francis Augustus Storey *
Frentano
Friesland
Garnet
George Hardy
Germania *
Gill's Gloriosa
Goliath
Grab Ya *
Gunborg
Gwen Bell
Hachmann's Anastasia
Hachmann's Kristina
Haithabu
Halfdam Lem
Heat Wave
Heinje's Venezia
Helen Druecker
Hollandia
Horizon Serenity *
Ilam Apricot
Inheritance
Irmelies
Isadora
Isobel Baillie
Jan Dekens
Janet Ward
Jean Lennon
Jean Marie Variegated
Jeanne Yvonne
Jenice Coffey
Johnny Bender
Julie Titcomb
Justa Pink
Kareness
Kathe Heinje
Kathy Ann Pieries
Kay Too
KSW
Lady Longman
Leonardslee Giles
Lilian
Loder's White
Lou-John Gem
Madah Jean
Margaret Mack
Marion
Mary-Ed
Maureen Ostler
Melville
Miss Kitty
Mistake
Mrs E C Stirling (sister of Pink Pearl)
Newcomb's Sweetheart
Nicandra Newman
Orrie Dillie
Patricia Jacobs *
Peggy Bannier
Pink Goliath
President Kennedy
Pride of Roseburg *
Princess Debiann
Professor Hugo de Vries
Professor J. H. Zaayer
Qualicum's Pride
Queen Mary
Record
Reverend Paul *
Red Walloper *
Rhododendron niveum
Robert Korn
Romilda
Rotha
Scandinavia
Seraphine
Shalom
Shari Laurel
Sheer Enjoyment *
Sierra Sunrise
Sigrid
Souvenier de Docotr S. Endtz
Standishii
Titness Belle
TT116
Twins Candy
Virgo *
Vonnie Stockman
Walküre
Walloper *
Whidbey Island
White Swan
William Avery *

Despite having created this suspected polyploid list, we believe that over 25% would not test as polyploid. 'Fragrant Sensation', 'Grab Ya', 'Pride of Roseburg', and 'Sheer Enjoyment' having both parents as tested tetraploids are almost certainly polyploids. We have marked using an * the dozen or so we think are the most likely (almost certainly) polyploids.

Most in this list are known to have at least one polyploid parent, be a sibling of a polyploid, or be a parent of one or more polyploids. However, both triploid and tetraploid hybrid large leaf elepidotes are known to be capable of producing diploid offspring when the other parent is a diploid. Many hybrids on our suspected polyploid list have one parent suspected of being a diploid. In other words, a diploid can have a polyploid parent or sibling. Moreover, two diploid parents can produce a polyploid offspring so having a polyploid offspring does not insure either parent is a polyploid.

If one excludes known or suspected polyploid hybrids listed above, creating a list of 100 suspected polyploid named elepidote hybrids, where more than 20% would test as polyploid, would be difficult. In fact, it is highly likely that most attempts at such a list of 100 named elepidote hybrids would include very few if any additional polyploids.

In other words, we speculate that nearly all (over 90%) named polyploid elepidotes hybrids named prior to this post appear in this single post. This is almost certainly the case for polyploid elepidotes hybrids named prior to 2000. The chances there were more than 200 polyploid elepidote hybrids named prior to 2000 are low. The chances there were more than 50 tetraploid elepidote hybrids named prior to 2000 are even lower.


Figure 2: Offspring from Triploids (Pink Pearl)

In short there are no rules of thumb for guessing the ploidy of the offspring for hybrid large leaf elepidotes if the parents are of mixed ploidy levels or either parent is a triploid or pentaploid.

Diploid X diploid will almost always (but not always) create diploid offspring.

Tetraploid X tetraploid will almost always (but not always) create tetraploid offspring.

However, diploid X tetraploid and tetraploid X diploid, which are normally associated with producing triploid offspring, are known to often produce a combination of diploids, triploids, and tetraploids when working with hybrid large leaf elepidotes.

Triploids, Fertile Triploids, and Triploids as the Progeny of Triploids

Triploids are normally believed to be produced by one of two mechanisms.

Two diploids can cross where one diploid parent instead of providing one set of chromosomes provides two resulting in an offspring that has 3 sets of chromosomes. This is commonly referred to as the unreduced mechanism for creating triploids.

Ploidy results suggest that triploids such as 'Anita Gehnrich', 'Grace Seabrook', 'Markeeta's Flame', 'Markeeta's Prize', 'Solaridity', and 'Taurus' were most likely created by this unreduced mechanism.

On the other hand, a diploid parent and a tetraploid parent can cross where the diploid parent provides one set of chromosomes and the tetraploid parent provides two sets of chromosomes resulting in an offspring with 3 sets of chromosomes. This is referred to as the normal meiosis interploidy mechanism for creating triploids.

Ploidy results suggest that triploids such as 'Anna Rose Whitney', 'Cotton Candy', 'El Camino', 'Hank's Folly', 'Julia Caroline, 'Lady of Spain', 'Lucky Strike', 'Lydia', 'Opal Thornton', 'Platinum Pearl', 'Rwain', 'Steredenn', 'Sugar Pink', 'Super Dog', and 'Van' were most likely created by this normal meiosis interploidy mechanism.

Triploids are commonly believed to always be sterile as both seed parents and pollen parents. Yet offspring are documented for triploids such as 'Anna Rose Whitney', 'Betty Wormald', 'Broughtonii', 'Cotton Candy', 'Cynthia', 'Gomer Waterer', 'Lydia', 'Pearce's American Beauty', 'Phyllis Korn', 'Pink Pearl', 'Platinum Pearl', 'Rwain', 'Solidarity', 'Taurus', and 'Val d'Aulnay'. See figure 1.

Triploids such as 'Pink Pearl', 'Phyllis Korn', 'Rwain', and 'Taurus' appear to be partially fertile as both seed and pollen parents. See figure 2.

In fact, triploids can be the progeny of triploids. Based on parental documentation, 'Broughtonii', 'Pink Pearl, 'Gomer Waterer', and 'Phyllis Korn' represent four consecutive generations of triploids. See figure 1.

Three sports of the triploid 'Pink Pearl' were ploidy tested. 'Ebony Pearl' and 'Topsvoort Pearl' tested as triploid whereas 'Mother of Pearl' tested as diploid. See figure 2.

Diploids can be the progeny of triploids. The diploids 'Graf Zeppelin', 'Hurricane', 'J.G. Millais', and 'Summer Peach' are documented to have a triploid parent. In the case of 'Graf Zeppelin', the triploid 'Pink Pearl' is documented as the seed parent. See figure 2. Although a diploid, 'Graf Zeppelin' exhibits characteristics often associated with named polyploids.

Tetraploids can be the progeny of triploids. 'Countess of Derby', a tetraploid, is documented to have 2 triploid parents, namely 'Pink Pearl' and 'Cynthia'. The tetraploids 'Antoon van Welie', 'Gentle Giant', and 'Grand Slam' are documented to have a triploid parent. In the case of 'Antoon van Welie', the triploid 'Pink Pearl' is documented as the seed parent. See figure 2.

Marc Colombel donated some of his suspected polyploid hybrid seedlings for testing. Noteworthy is that four seedlings of 'Rwain' X ‘L’Engin’ tested as tetraploid. 'Rwain' the seed parent, is a triploid. 'L'Engin', the pollen parent, is a tetraploid. Moreover, three seedlings of 'Horizon Monarch' X 'Rwain' tested as tetraploids but one seedling tested as triploid. 'Horizon Monarch' is a tetraploid.

Figure 2 suggests that a triploid parent, for instance 'Pink Pearl', can produce offspring that are diploids, triploids, and tetraploids. Figure 1 suggests that pentaploids are also possible from a triploid parent.

In the 1930's, C. J. Darlington showed that triploids could be fertile. Moreover Darlington confirmed a third mechanism for creating triploids. Darlington showed that during meiosis triploids chromosomes may split forming a bell-shaped curve distribution. This means that although there are a few cells formed with 1x and 2x chromosomes, most are closer to the midpoint of 1.5x. So in a few cases, a triploid parent can act as a diploid contributing 1 set of chromosomes or as a tetraploid contributing 2 sets of chromosomes.

Our ploidy results, when combined with the documentation of parentage, strongly suggest this third distributive meiosis mechanism does occur for fertile triploid large leaf elepidote Rhododendrons.

Hans Eiberg has determined in controlled lab experiments that for Rhododendrons hybrid triploid pollen is sometimes as viable as any hybrid diploid pollen.

Tetraploids and Diploids as the Progeny of Tetraploids

Tetraploids such as 'Doreen Gale', 'Gorgeous George', and 'Legend' have been created by the normal meiosis mechanism where both parents are tetraploids.

Tetraploids such as 'Horizon Monarch', 'Lem's Monarch', 'L'Engin', 'Point Defiance', and 'Very Berry' may have been created by the unreduced mechanism of a diploid parent with the other parent being a tetraploid.

Justin Ramsey's work with newly created neotetraploids suggests that such neotetraploids may experience irregular meiosis. Ramsey suggests that in some instances a neotetraploid may contribute only one set of chromosomes to the offspring. For the purposes of this article, we refer to this as the super-reduced mechanism.

Diploids such as 'Orange Leopard', 'Rendezvous', and 'Stony Brook' may have been created by this super-reduced mechanism. In the case of 'Rendezvous', the tetraploid 'Marinus Koster' is documented as the seed parent.

Noteworthy is that one seedlings of 'Horizon Monarch' open pollinated tested as diploid. The actual plant of 'Horizon Monarch' that was the parent of this particular diploid seedling tested as tetraploid. Other seedlings from the same seedpod tested as tetraploid.

Our ploidy results suggest that tetraploids may produce diploid, triploid, tetraploid, and pentaploid offspring.

To read more about the super-reduced mechanism visit Ploidy Reduction in Blackberries" by Kristine Naess or Cytogentics of Rhubus: Meiotic Instability in Some Higher Polyploids by Maxine Thompson.

Normal, Unreduced, Super-reduced, and Distributive Meiosis: By the Numbers

A diploid Rhododendron has 26 chromosomes. Normally a diploid Rhododendron as a parent splits in half contributing 13 chromosomes to the offspring.

A tetraploid Rhododendron has 52 chromosomes. Normally a tetraploid Rhododendron as a parent splits in half contributing 26 chromosomes to the offspring.

A triploid Rhododendron has 39 chromosomes. Half of 39 is between 19 and 20. Darlington showed that if a triploid having 39 chromosmes were to split it would split mainly 19/20 but, also to ever decreasing occurrences, 18/21, 17/22, 16/23, 15/24, 14/25, and 13/26 where the splitting as 13/26 occurs the least. This splitting would form a bell shaped curve between 13 and 26.

Thus, in principle, for Rhododendrons

diploid X diploid usually results in a diploid since 13 + 13 = 26.

tetraploid X tetraploid usually results in a tetraploid since 26 + 26 = 52.

diploid X tetraploid usually results in a triploid since 13 + 26 = 39.

diploid X unreduced diploid can in a few instances result in a triploid since 13 + 26 = 39.

unreduced diploid X tetraploid can in a few instances result in a tetraploid since 26 + 26 = 52.

diploid X super-reduce tetraploid can in a few instances result in a diploid since 13 + 13 = 26

diploid X triploid can in a few instances result in diploid since 13 + 13 = 26 or in a triploid since 13 + 26 = 39.

triploid X tetraploid can in a few instances result in triploid since 13 + 26 = 39 or in a tetraploid since 26 + 26 = 52.

Noteworthy is other researchers found that the offspring of triploids are often aneuploids. For Rhododendrons, an aneuploid would have a number of chromosomes slightly more or less than 26 (2x), 39 (3x), 52 (4x), 65 (5x) or other multiples of 13 (x=13). The unstable meiosis associated with triploids and neotetraploids most likely means that some of the Rhododendrons listed above as diploids, triploids, or tetraploids do not have exactly 26, 39, or 52 chromosomes but instead may have a chromosome count close to these numbers. Flow cytometry being a method of weighting sets of chromosomes rather than counting the number of chromosomes is not well suited to separating euploids from aneuploids when the samples tested involve interactions between a wide range of species within the same genus.

Summary

Named hybrid large leaf elepidote polyploid Rhododendrons have played an important role in the garden for more than 150 years. The physical characteristics associated with polyploid Rhododendrons have proven to be highly desired by gardeners since their introduction by Broughton, Standish and Noble, and Waterer.

The ploidy of more than 100 named hybrid large leaf elepidote Rhododendrons is listed above.

Although to date all species of large leaf elepidote Rhododendrons have tested as diploid species more than 50 named hybrid large leaf elepidote Rhododendrons tested as polyploids.

Approximately 2/3 of the named named hybrid large leaf elepidote Rhododendrons which tested as polyploids tested as triploids with the remaining 1/3 testing as tetraploids.

Triploids can be fertile as both seed and pollen parents. Triploids are able to produce diploid, triploids, tetraploid, and pentaploid offpsring.

Tetraploids are able to produce diploid, triploid, tetraploid, and pentaploid offpsring.

The mechanisms of normal, distributive, unreduced, and super-reduced meiosis are discussed.

This research used as a foundation work done by the following:

Hybridization of Rhododendron Elepidote Polyploids by Jim Barlup

Rules of Engagement: Have Pollen - Will Travel by John and Sally Perkins

Ploidy Levels and Relative Genome Sizes of Diverse Species, Hybrids, and Cultivars of Rhododendron by Jeff R. Jones, Thomas G. Ranney, Nathan P. Lynch, and Stephen L. Krebs

Ploidy Breeding and Interspecific Hybridization in Spathiphyllum and Woody Ornanamentals by Tom Eeckhaut

Meiosis in Polyploids Part I. Triploid and Pentaploid Tulips by W. C. F. Newton and C. D. Darlington

Neopolyploidy in Flowering Plants by Justin Ramsey and Douglas W. Schemske

Posts for each sample ploidy tested are available on the Rosebay Blog. Posts have been grouped using tags to promote easy viewing of related posts. Please weigh in by exploring these posts to discover the wonderful world of ploidy in the Rhododendron garden.

On page 13 of 2001 Rhododendron Camellias and Magnolia Dr. Ray Thornton writes the following:

"I thought that these seedlings might be the record holders for rapid growth but this title instead may pass to 'Lem's Pink Walloper' X R. diaprepes 'Gargantua', from the RHS Seed Exchange, which is growing at a extraordinary rate this spring.

The 2010 Rhododendron, Camellias, and Magnolias references the following as exceptional plants of 2009

Taurus
Grace Seabrook
Phyllis Korn
Horizon Monarch

Also mentioned are 2 new Award of Merit Winners:

'Brimble' has as a parent the famous R. griffthianum grown by Lionel Foretescue at the Garden House.

'Forest Sprite' is a augustinii X keiskei and the following is noted.

"The cross was tried several times without success, surprising as both parents are from the Triflora series. Eventually just one seedling was reared in 2002."


John and Sally Perkins

Clones may not be Identical

"Using DNA sequencing techniques that can decode the complete genome of an organism in one go (so-called ‘whole genome sequencing’) the researchers analyzed ‘clones’ of the small flowering plant ‘thalecress’ (Arabidopsis). They found that observable variations in regenerant plants are substantially due to high frequencies of mutations in the DNA sequence of these regenerants, mutations which are not contained in the genome of the parent plant."

Why plant 'clones' aren't identical

'Margaret Abbott' is a Tetraploid

'Margaret Abbott' (Frank Abbott) [4x]
Rhododendron prinophyllum [2x] X Rhododendron calendulaceum [4x]
Spring 2009 Saxtons River, VT
S and J Perkins

Rhododendron 'Margaret Abbott', which is a Frank Abbott hybrid documented as Rhododendron prinophyllum X Rhododendron calendulaceum, has been determined to be a tetraploid using flow cytometry by

Dr. João Loureiro, Dr. Silvia Castro, José Cerca Oliveira, and Mariana Castro
Plant Ecology and Evolution Group,
Centre for Functional Ecology,
Department of Life Sciences,
Faculty of Science and Technology,
University of Coimbra, Portugal.

Rhododendron 'Margaret Abbott' was named by Frank to honor his wife. Frank was amazed he crossed a pink with a yellow to produce this lone fragrant ruffled white flower with a yellow flare. See A Love Affair With A Flower by Marge Runnion. See Frank Abbott's Village of Azaleas by John and Sally Perkins.

Notice in the image above on the flower facing forward, 'Margaret Abbott' has, at the end of the stamens, tagged anthers, such anthers rarely appear on a deciduous azalea. 'Margaret Abbott' is known to be partially seed fertile but does not appear to have viable pollen.

Notice, also, for 'Margaret Abbott' that the diploid is the seed parent and the tetraploid is the pollen parent. For deciduous azaleas, diploids usually accept pollen from tetraploids but tetraploids usually reject pollen from diploids. See Rules of Engagement by John and Sally Perkins.

In the case of the tetraploid 'Margaret Abbott', a diploid crossed with a tetraploid produced a tetraploid indicating that unreduced meiosis may have occurred for the diploid seed parent. In other words, 'Margaret Abbott' having 52 chromosomes received something on the order of 26 chromosomes from the diploid Rhododendron prinophyllum and 26 chromosomes from the tetraploid Rhododendron calendulaceum. See Unreduced Meiosis. See Ploidy of Deciduous Azaleas Species.

In every other case we have tested where a diploid deciduous azalea is crossed with a tetraploid deciduous azalea, the resulting offspring have been triploids having 39 chromosomes receiving 13 chromosomes from the diploid seed parent and 26 chromosomes from the tetraploid pollen parent. See 2X4 for Deciduous Azaleas. See Normal Meiosis.

Natural interactions of diploid deciduous azalea species and tetraploid diploid deciduous azalea species do occur in places such as Audra State Park. Plants that appear to be interploidy hybrids have tested as triploid and tetraploid. The ploidy results for 'Margaret Abbott' indicated that unreduced gametes of the diploid seed parent may be one of the mechanism causing tetraploids to be produced by diploid X tetraploid interaction. See Audra State Park: Ploidy Haven. See Rhododendron prinophyllum by Elizabeth Carlhian. See Rhododendron arborescens by Susan Clark. See Rhododendron calendulaceum by Joe Bruso.

The hybridizers of the Ghents, including some done by Ed Mezitt, the Rusticas, and the Northen Lights series crossed diploid and tetraploid deciduous azaleas. See Ghent. See Rustica. See Mezitt.

For large leaf elepidote hybrid Rhododendrons we have discovered several instances where a diploid X tetraploid results in tetraploids as well as triploids and diploids. For instance, Rhododendron 'Horizon Monarch', which is a Ned Brockenbrough hybrid documented as 'Nancy Evans' x 'Point Defiance', has been determined to be a tetraploid. 'Nancy Evans' has been determined to be a diploid and 'Point Defiance' has been determined to be a tetraploid. See 2X4 for Large Leaf Elepidotes. See 4X2 for Large Leaf Elepidotes.

For large leaf elepidote hybrid Rhododendrons we have discovered fertile triploids and the offspring of these triploids can be tetraploids. For instance, Rhododendron 'Countess of Derby', which is a 1913 Henry White hybrid documented as 'Pink Pearl' x 'Cynthia', has been determined to be a tetraploid. Both 'Pink Pearl' and 'Cynthia' have been determined to be triploids. See It is 1913 So What Do You Do? by John and Sally Perkins. See Fertile Triploids. See Pink Pearl.

For large leaf elepidote hybrid Rhododendrons we have discovered tetraploids can produce diploid offspring in the first generation. See Super Reduced Meiosis.

Although there are no known polyploid elepidote species, many elepidote hybridizers, including Barlup, Bones, Brack, Briggs, Brockenbrough, Broughton, Bruns, Colombel, Croux and Fils, de la Sablière, Endtz, Evans, Felix and Dijkhuis, Fujioka, Greer, Gehnrich, Hachmann, Hartman, Heinje, Henny and Wennekamp, Hobbie, Kavka, Kehr, Korn, Koster, Lem, Loder, Lofthouse, Mangles, Markeeta, McCullough, Mossman, Murcott, Naylor, Patterson, Pearce, Rabideau, Sanders, Schannen, Seabrook, Standish and Noble, Stead, Stockman, Thornton, vanNes, VanVeen, von Martin, Walton, Waterer, White, Whitney, Wilson, and Woodward have worked with or produced ployploid elepidotes hybrids and in some cases are best known for these polyploid hybrids.

Clarence Towe aided us in confirming that the plant pictured above is 'Margaret Abbott'.

To see a poster on the ploidy results (Click on the poster image to enlarge):

Ploidy Research Poster by José Cerca Oliveira.

To see the research team:

Research Team of Dr. João Loureiro, Dr. Silvia Castro, José Cerca Oliveira, and Mariana Castro.

To see other images of Frank Abbott's azaleas visit the following:

Abbott Azaleas by S & J Perkins.

The "In The Collections" web page of the Arnold Arboretum includes a reference to our ploidy research.

Summary of Ploidy Levels

Diploid Rhododendron molle,
Diploid Rhododendron prinophyllum,
Diploid 'Frank Abbott',
Diploid "Jane Abbott" (grex),
Diploid 'Nancy Evans',
Triploid 'Cynthia',
Triploid 'Pink Pearl',
Tetraploid Rhododendron calendulaceum,
Tetraploid 'Countess of Derby',
Tetraploid 'Horizon Monarch',
Tetraploid 'Margaret Abbott',
Tetraploid 'Point Defiance'

Source: John Abbott

Ploidy Results by Groups

Rhododendron Species,
Diploid Deciduous Azaleas,
Triploid Deciduous Azaleas,
Tetraploid Deciduous Azaleas,
Diploid Large Leaf Elepidotes,
Triploid Large Leaf Elepidotes,
Tetraploid Large Leaf Elepidotes,
Diploid Lepidotes,
Triploid Lepidotes,
Tetraploid Lepidotes,
Diploid Everegreen Azaleas,
Triploid Evergreen Azaleas,
Diploids,
Triploids,
Fertile Triploids,
Tetraploids,
Ghents,
Northern Lights, and
Rusticas

The following people and organizations donored samples for this reasearch:

John Abbott,
Vivian Abney of East Fork Nursery,
Arnold Arboretum,
Audra State Park,
Bartlett Arboretum,
Jim Barlup,
Bruce Clyburn,
Jane Brooks,
Joe Bruso,
Werner Brack,
Ned Brockenbrough,
Canobie Lake, NH,
Dick Cavender,
Connecticut College Arboretum,
Marc Colombel,
Mike Creel,
Al Fitzburg,
Robert Fox,
Harold Greer of Greer Gardens,
George Hibben,
Highstead Arboretum,
Don Hyatt,
Lindy Johnson of Appalachian Native Plants,
Richard Jaynes of Broken Arrow Nursery,
Doug Jolley,
Fred Knippel,
Longwood Gardens,
Ron Miller,
Dick Murcott,
Planview Nursery,
John and Sally Perkins,
Ron Rabideau of RareFind Nursery,
Ellie Sather of Whitney Gardens,
Stoddard Blog, NH,
John Thornton,
Hendrik Van Oostand of Azaleatuin,
Kathy Van Veen of Van Veen Nursery

John and Sally Perkins

It is 1913 so What Do You Do?

It is a Beautiful Spring Day in 1913 so What Do You Do?
John and Sally Perkins


Figure 1: Triploids can be Fertile and can create a Bidirectional Pathway Between Ploidy Levels

In spring 1913, George V is the first Windsor King of England, Woodrow Wilson is serving his first term as President of the United States, and World War I is a future event. The 2 most popular Rhododendrons in the world are 'Pink Pearl', a 1890's Waterer hybrid, and 'Cynthia', a 1850's Noble and Standish hybrid. On a beautiful spring day in 1913 if you are Henry 'Harry' White, a nursery manager in Sunningdale, England you cross 'Pink Pearl' by 'Cynthia'. You later name a seedling from this cross 'Countess of Derby'.

In spring 1961, John Kennedy is the young handsome President of the United States and Vietnam is a country unknown to most Americans. On a beautiful spring day in 1961 if you are Harold Greer, living in Eugene, Oregon, you self 'Countess of Derby'. You later name a seedling from this cross 'Trude Webster'.

In spring 1969, Richard Nixon is the President of the United States and Watergate is simply an office building in the DC area. On a beautiful spring day in 1969 if you are Robert Korn in Renton, Washington, you place the pollen from 'Gomer Waterer', a 1900 Waterer 'Pink Pearl' hybrid, onto 'Diane'. You later name a seedling from this cross 'Phyllis Korn'.

In spring 1988, George H. Bush is the Vice President of the United States and Iraq is simply a country somewhere in the Middle East. On a beautiful spring day in 1988 if you are Jim Barlup, living in Bellevue, Washington, you cross 'Whitney's Late Peach' by 'Phyllis Korn'. You later name a seedling from this cross 'Summer Peach'.

In spring 2001, George W. Bush is the President of the United States and the Twin Towers in New York City are still standing. On a beautiful spring day in 2001 if you are Jim Barlup, living in Bellevue, Washington, you cross 'Phyllis Korn' by 'Trude Webster' to create several viable offspring.

So what have you done starting in 1913?

Well you took 2 fertile triploids from the 19th century, namely 'Pink Pearl' and 'Cynthia' and created a tetraploid, namely 'Countess of Derby'. You then selfed the tetraploid 'Countess of Derby' creating a tetraploid, namely 'Truder Webster'. You then placed pollen from the triploid 'Gomer Waterer' onto a diploid seed parent, namely 'Diane' creating a triploid, namely 'Phyllis Korn'. You then used the pollen of a triploid, namely Phyllis Korn' to create a diploid, namely 'Summer Peach'. You then placed the pollen of the tetraploid 'Trude Webster' onto the triploid seed parent 'Phyllis Korn' and produced a series of pentaploid seedlings. See figure 1.

By doing so you ended the myth that triploids are always sterile showing that triploids can be both seed and pollen parents. Moreover, triploids, when used in hybridization, produce both reduced and unreduced gametes. You demonstrated that triploids provide a pathway for the bidirectional transfer of genes between diploids, triploids, tetraploids, and pentaploids.

It took you a few beautiful spring days doing crosses, a few changes of names and addresses, nearly 90 years, and a team of young researchers at the University of Coimbra in Portugal to confirm your results but all in all not a bad piece of work.

Summary of Ploidy Levels

Diploid 'Diane',
Diploid 'Madame Carvalho',
Diploid 'Summer Peach',
Triploid 'Broughtonii',
Triploid 'Cynthia',
Triploid 'Gomer Waterer',
Triploid 'Pink Pearl',
Triploid 'Phyllis Korn',
Tetraploid 'Countess of Derby',
Tetraploid 'Trude Webster', and
Pentaploid Seedlings of 'Phyllis Korn' X 'Trude Webster'

Flow cytometry to determine ploidy levels performed by

Dr. João Loureiro, Dr. Silvia Castro, José Cerca, and Mariana Castro
Plant Ecology and Evolution Group,
Centre for Functional Ecology,
Department of Life Sciences,
Faculty of Science and Technology,
University of Coimbra, Portugal.

The following people and organizations donored samples for this reasearch:

John Abbott,
Vivian Abney of East Fork Nursery,
Arnold Arboretum,
Audra State Park, WV,
Jim Barlup,
Barlett Arboretum,
Jane Brooks,
Joe Bruso,
Canobie Lake, NH,
Dick Cavender,
Werner Brack,
Ned Brockenbrough,
Marc Colombel,
Bruce Clyburn,
Connecticut College Arboretum,
Mike Creel,
Al Fitzburg,
Robert Fox,
Harold Greer of Greer Gardens,
George Hibben,
Highstead Arboretum,
Don Hyatt,
Lindy Johnson of Appalachian Native Plants,
Richard Jaynes of Broken Arrow Nursery,
Doug Jolley,
Fred Knippel,
Longwood Gardens,
Ron Miller,
Dick Murcott,
John and Sally Perkins,
Planeview Nursery,
Ron Rabideau of RareFind Nursery,
Ellie Sather of Whitney Gardens,
Stoddard Blog, NH,
John Thornton,
Hendrik Van Oostand of Azaleatuin,
Kathy Van Veen of Van Veen Nursery

21st Century Chapter Web Site

The Dream of a 21st Century Chapter Web Site
by John and Sally Perkins

If we were starting over from scratch and building a chapter web site for the 21st century, we would concentrate our efforts on having an online presents able to be read by and contributed to by any chapter member who knew how to use email. Our goal would be maximize the number of chapter members who contribute to the chapter site relying on the fact that most members know how to email and most own a digital camera.

Digital Image Presentations

Digital Presentations: Some Hints on Preparation and Delivery
by Sally and John Perkins

Digital image presentations have replaced traditional slide film based talks at most conferences and many chapter meetings. The cost, quality, and availability of digital cameras, digital projectors, and digital presentation software are at the point that the advantages of such digital presentations far outweigh the disadvantages.

In principle, digital presentations are quite similar to traditional presentations in terms of content and the skills required preparing and delivering. In general, the audience appreciates a well organized talk consisting of beautiful images and relevant information presented in an entertaining and timely fashion.

In practice, good images are the backbone of any presentation. Digital cameras have improved to the point that the quality of digital images is more than good enough for projection at a meeting or conference. Here are some suggestions for making good use of these images in a digital image presentation.

Plan to present 2 to 3 images per minute.

We have found that for presentations lasting 45 minutes to an hour that an image every 20 to 30 seconds is often enough to keep the presentation moving while still allowing adequate time to verbally present related content.

Six images per minute for a rapid fire ten minute presentation on say the flora of a given area is possible but only practical for someone who has given many digital presentations. Upwards of 180 images in an hour presentation is possible but again only for someone who is experienced in giving digital presentations.

Ninety images is a good upper bound for a first time digital presentation where an hour has been allotted for the presentation and questions.

Timed presentations

Most digital presentation software allows an option to control the time each image is viewed. A software controlled timed presentation is excellent for a conference where keeping on schedule is extremely important. We now use timed controlled presentations for all our talks where we allow ourselves the option of advancing to the next image manually. This allows us to be certain that a given presentation will last no longer than our desired time upper limit.

Repeat an image if more time is required

For conference presentations where being on schedule is of the utmost importance we use a fixed time per image near 20 seconds. If we want any given image to appear longer than this we merely load a copy of the same image, possibly multiple copies, sufficient for the chosen time period. When we give a 2-person talk we often repeat an image as a transition between the speakers.

Place a title at the top left on each image.

One of the major advantages of digital over slide film based presentations is the ease of adding text to images.

Titles should be placed at the top of the image and preferably always in the same general location. We prefer the top left of the image for all our image titles. We find titles using white print and a green background work well for most plant images. Selection of the font size will depend on the size of the room, as well as the projector’s resolution, and it’s always best to err on the larger size.

Titles centered at the bottom of an image are excellent for books, articles, web sites, and small round table presentations but titles on the top are far more visible for a larger audience where the seating is by rows. Titles at the top of an image are much easier for the audience in the back of the room to see.

Avoid software tricks and special effects

In general first time presenters should avoid tricks such as moving, fading, spinning, blinking, or color changing titles. In fact, software tricks are best kept to a minimum until one gains experience doing digital presentations.

Special effects in the hands of experienced presenters can be very useful for making a point or for humor, but, in general, the presenter has to be able to act as the straight man for these effects to work well requiring a sense of timing that most less experienced presenters lack. In fact if overused special effects may have the opposite effect on the audience becoming distracting and non-humorous.

We rarely use such effects in our presentations.

Images titles as lecture notes

We use the titles on the images as a substitute for written lecture notes. Although we keep the titles brief, we incorporate enough information in the title to remind us of why the image is included.

This greatly increases our ability to keep the presentation moving while insuring we cover all of our major talking points.

Images titles as handout

We prepare a written handout that is basically a list of the image titles. Having the titles on the images allows the audience to focus their attention on the images rather than having to refer to the handout.

This also allows us to have the lights turned down lower than would be practical if the audience had to frequently refer to the handout during the presentation. Many less expensive and older digital projectors need a well darkened room.

Image as background to bulleted text

Text based digital slides are easily added to digital presentations. Such slides are useful in the introduction of a presentation or during transition periods in a presentation.

In general, a background image relating to the text being presented greatly enhances the visual effect of such slides.

Collages for transitions

The digital software packaged with most digital cameras allow the easy creation of simple collages as digital images. Collages can be useful as a starting or transition slide in a presentation.

Maps for reference

Web based software supports the creation of maps as digital images. Maps can be can be useful as a starting, reference, or transition slides in a presentation.

Starting presentation with the first digital slide

Map, text, or collage based slides allow the presenter to coordinate the beginning of the talk with the first digital slide. In our opinion, nothing moves a talk forward and gets the audience on board more than the presentation of the first slide and then the transition to the second slide.

Learning to blend the beginning of verbal and visual portions of a presentation is the key to leading the audience on your digital journey.

Prior to presentation review

A big advantage of digital presentations is the ease in reviewing the finalized version. All one needs is to set the computer monitor at the same resolution as the digital projector. Whereas a slide projector is required to review the sequence in its final form costing precious bulb time. Three seconds per slide is usually all that is needed to review the visual portion of the presentation including the quality of the images, the clarity of the titles, and the basic sequence of the digital journey.

We find five to ten seconds of review per slide is needed to convince ourselves that we are ready to talk to the given set of slides. We find that slight modifications to the titles are sometimes required at this point for the mnemonics needed especially for transition slides.

Removing lower quality images

We have learned that removing lower quality images greatly improves the overall presentation. Marginally passable images that are considered essential for the theme are often just not included, which avoids having to apologize for the image quality. Before finalizing a presentation we digitally project the sequence of images. Some images that look fine on a monitor simply do not translate well to the big screen.

Maximizing the real estate

We finalize a presentation by making certain we take full advantage of the resolution of the digital projector. We crop our images to have the same ratio, normally 4 by 3, as the digital projector, thereby allowing the horizontal based images to fill the screen. We reduce the resolution of the images to match the native resolution of the digital projector, often 1024 by 768. We set our laptop to this resolution also.

Presentation from the hard drive

We have found that placing the presentation on the hard drive rather than on a CD or thumb drive reduces the potential for lag time on the transition between slides. Reducing the resolution of images to be no larger than what is supported by the projector also reduces the potential for such delays.

Color variation

One of often sited, disadvantage of digital presentation is the color varies depending on the laptop and the projector. When one is using their own equipment this can be dealt with during the review process but becomes much more of an issue when using provided equipment. It is worthwhile to have someone familiar with color balance and the projector’s menu options on hand for setup. Most frequently there will be too much blue tones resulting from a combination of less expensive digital cameras and video signal of the laptop.

The clicker

Clickers often have a button for closing (terminating) a presentation as well as buttons for advancing forwards and backwards between slides. Unintentional use of the close button can be an issue when using provided equipment.

The camera

A digital camera of more than 3 mega pixels is adequate for producing images good enough for digital projection. Cameras designed to capture the nuances of human skin tone (many inexpensive point and shoots) will require more software to restore the actual color.

The projector

Since image quality and color is more important than sharpness of text, we recommend a DLP projector having a native resolution of at least 1024 by 768.

The software

Personal preference combined with what software you already have loaded on your home computer are the biggest factors in choosing what software to use to prepare a digital presentation. PowerPoint is the default choice of many especially those used to the Microsoft work environment and it is more than adequate. We prefer a combination of the program Picasa for storing, titling, and organizing of the images, JPEGCrop for cropping the images, and Irfanview for finalizing the presentation format.

Our preparation process

We have found that finding the images, titling the images, and ordering the images are the major factors in how long it takes to put a presentation together. Cropping of the images, producing the handouts, and the finalized presentation are only done after the more time consuming steps are completed and reviewed.

We store all our images using Picasa. Picasa supports titling of images as captions. The caption is stored as metadata or data within the data of the image file rather than the title becoming pixels in the image. In our work, once the title is entered as a caption within the image information, we can choose to show the image without or without the caption since its stored in a different part of the file than the actual pixel information. The caption can be changed without affecting the image pixel information.

Picasa supports searching on the file name of the images as well as the caption and sorting by date of storage. This is invaluable in locating images.

Picasa supports organizing images in virtual folders. In other words the images can be added and organized into a named folder without physically moving the images on the hard drive. Moreover, once in a virtual folder, the images in that folder can be reordered using drag and drop. The caption for an image in the virtual folder can be added or modified.

Picasa supports viewing as a slide show the images stored in a virtual folder. This slide show can be viewed with or without titles.

Picasa allows exporting this slideshow as a text file of captions and associated images that can be imported and used by Irfanview.

Picasa supports quick fixing the quality of image. Picasa supports creating simple collages.

Irfanview, also, supports viewing the images as a slide show. Using Irfanview we can generate a timed slideshow executable that can run without requiring any other software. Irfanview supports the use of the caption stored in an image to be placed in the upper left hand corner of each image using a green background and white letters. Options for location, font, font size, color of text and different backgrounds are available.

Before finalizing the presentation as an executable using Irfanview we crop the images using a batch edit tool such as JPEGCrop or individually with the newer version of Picasa and resize the images using Irfanview.

We review the finalized presentation using a laptop and a digital projector and make any final modifications to the images or titles using Irfanview.

We finalize the handout by editing the file of titles using Word.

Worth mentioning is everything we do to the images inside Picasa is work to improve the quality of our set of stored images. This work is a permanent part of our image collection and useful in creating future presentations.

On the other hand, the work we do inside Irfanview is for the sole purpose of finalizing the given presentation.

Conclusion

Although there are as many ways to prepare and give a good presentation as there are presenters, we have found the hints presented above useful in improving the quality of our digital image presentations.

Golf and Rhododendrons

Enjoy an article on the Rhododendrons that Dean Barber contributed to the Concord Country Club.

Dean Barber Rhododendron's at the Concord Country Club

Rules of Engagement

Rules of Engagement: Have Pollen - Will Travel
by John and Sally Perkins, Salem, NH

Click on image to enlarge


Species of Diploid Clade
Rhododendron cumberlandense in center
Clockwise from top left: periclymenoides, prunifolium, prinophyllum, viscosum, flammeum
Not shown: alabamense, arborescens, canescens, eastmanii, occidentale
S and J Perkins

Species of Tetraploid Clade
Rhododendron calendulaceum in center
Clockwise from top left: colemanii, luteum, atlanticum, pink austrinum, austrinum
S and J Perkins

'Margaret Abbott' (Abbott)
Rule #3: prinophyllum (diploid) X calendulaceum (tetraploid)
S and J Perkins

Crosses onto R. calendulaceum 'Cherokee', a tetraploid
Rule #4: Rejects pollen from diploids
Rule #2: Accepts pollen from other tetraploids
S and J Perkins

Bigger Than Normal Diploid Seedpod
Rhododendron arborsecens var. rubra, a diploid is next to 'Marydel', a tetraploid
S and J Perkins

The conventional wisdom, passed along in books, articles, and word-of-mouth, states “North American native deciduous azaleas, excluding Rhododendron vaseyi and canadense, interbreed freely”; however, the rules of engagement for these azaleas are far more complex when crossing diploid and tetraploid azalea species.

The 2 Clades

The latest work by Benjamin Hall and Tom Ranney indicates that native deciduous azaleas break into 2 major clades that correspond to their ploidy levels. For those unfamiliar with the discussion of clades and ploidy we will digress and explain that when genetic material is used to try to determine how closely related species are, the term clade refer to species that have a common ancestor. The analysis done so far, strongly suggest that there are 2 different clades when examining the deciduous azaleas. These clades seem to separate according to their ploidy level. The ploidy level refers to the number of chromosomes. Most rhododendrons and azaleas have a base number of 13 chromosomes (x=13) which is the number found in pollen and unfertilized seed. Here diploid deciduous azaleas are classified as having 2x=26 chromosomes, triploid deciduous azaleas are classified as having 3x=39 chromosomes, and tetraploid deciduous azaleas are classified as having 4x=52 chromosomes. The tetraploids have twice as much genetic material as the diploids, but they do not, based on genetic studies from Hall, have simply a duplication of the genetic material alone and the tetraploids and diploids have not been freely exchanging genes with each other for a long time. Triploids often result as a result of a cross between a diploid and a tetraploid.

The tetraploid clade includes Rhododendron atlanticum, austrinum, calendulaceum, colemanii, luteum (from Europe), and possibly, a pink-flowered species similar to austrinum. The diploid clade includes Rhododendron alabamense, arborescens, canescens, cumberlandense, eastmanii, flammeum, occidentale, periclymenoides, prinophyllum, prunifolium, and viscosum.

Although each are diploids, the two native deciduous azaleas Rhododendron canadense and vaseyi, as well as the Chinese and Japanese species of Rhododendron molle, do not belong to the diploid clade as described above. Benjamin Hall, Hans Eiberg, and K. A. Kron each found Rhododendron vaseyi to be only a distant relative of the other North American deciduous azaleas. Of the three, Rhododendron molle is the only one that has been used extensively to produce commercial hybrids involving the 2 clades described above. George Fraser and Harold Pellett each successfully crossed canadense X molle.

Rules of Engagement for Crossing Species in the 2 Clades

Rule #0: The rules of engagement for deciduous azaleas within these 2 clades are highly generalized guidelines. The rules focus on the ability to successfully create seedpods. Exceptions to these rules will occur. The only way to know for certain is to do the cross and let nature takes its course.

However, such exceptions are rare enough that hand crosses violating these rules are worthy of documentation and attempts should be made to see if the same result is repeatable between the same parents and other members of the 2 clades.

Rule #1: An individual plant in either the diploid clade or the tetraploid clade does not freely “self fertilize” to develop seeds. In those rare instances were selfing does occur, the offspring are seldom viable (if they germinate they die at a young age).

Rule #2: Species within a given clade freely cross in both directions. The resulting offspring are normally viable and fertile. The offspring normally reflect characteristics that are intermediate between the 2 species involved.

Rule #3: Species in the diploid clade freely accepts pollen from species in the tetraploid clade. The resulting offspring are often viable but usually sterile (bloom but do not produce seed) triploids. The offspring often reflect more characteristics of the tetraploid pollen parent. Offspring having pink or salmon colored flowers with a yellow blotch are not unusual. Deformed anthers, multiple petals and color streaks in the corolla are also frequently seen.

Rule #4: Species in the tetraploid clade normally reject pollen from species of the diploid clade. Exceptions occur but they are extremely rare.

Rule #5: Species in the diploid clade freely accepts pollen from Rhododendron molle. The resulting offspring are often viable but usually sterile diploids.

Rule #6: Triploids resulting from interaction between the diploid and tetraploid clades are more likely to accept pollen from species in the tetraploid clade than from species in the diploid clade. This rule is much more preliminary than the others above.

Rule #7: There are no known instances of Rhododendron vaseyi successfully interacting in either direction with species in either clade.

Rule of Thumb: To maximize you opportunity for producing seed where you have the option of parents in either direction, always use the deciduous azalea of the lower ploidy or same ploidy as the seed parent.

These rules of engagement support Hall's finding that the 2 major clades of North American deciduous azaleas are divided such that species grouped in a given clade are much more closely related to other species in that clade than they are to species that are more similar in appearance in the other clade. In other words, R. calendulaceum, a tetraploid, is more closely related to the other tetraploid species R. atlanticum, austrinum, colemanii, luteum, and “pink austrinum” than to the similar looking species R. cumberlandense, a diploid. The same is true for R. colemanii, a tetraploid, being closer to R. calendulaceum, atlanticum, austrinum, luteum, and pink austrinum than to the similar looking species R. alabamense, a diploid. Rhododendron atlanticum, a tetraploid, is closer to other tetraploids than the similar looking R. viscosum, a diploid. The “pink austrinum”, a tetraploid, is closer to other tetraploids than the similar looking R. canescens, a diploid.

Our Evidence

Richard Jaynes showed that selfing deciduous azaleas failed to produce seedpods in most instances and nonviable offspring resulted in those instances where seed was produced. We have failed in our attempts to self late blooming deciduous azalea species.

Many of the late blooming commercial hybrid azaleas produced by David Leach, George, Mary, and Jeff Beasley, Ed Mezitt, and Bob and Jan Carlson involve only species of the diploid clade combining R. arborescens, cumberlandense, prunifolium, and viscosum. We have found that species in the diploid clade cross in both directions.

Tom Dodd, Earl Sommerville, and Gene Aromi produced several good-doer hybrid azaleas for the south involving primarily calendulaceum and austrinum, both tetraploids. Fred Galle produced 'Choice Cream' using austrinum X atlanticum, both tetraploids. Bob and Jan Carlson produced hybrids using calendulaceum X luteum, both tetraploids. Ian Donovan produced a cross of atlanticum X calendulaceum, both tetraploids. We found we could cross in both directions R. calendulaceum 'Cherokee', 'Marydel', and 'My Mary' with Donovan's atlanticum X calendulaceum. Both ‘Marydel’ and ‘My Mary’ were shown later to be tetraploids in the lab. Prior to the ploidy testing, many hybridizers were aware that calendulaceum accepted pollen more easily from luteum, austrinum, and atlanticum than from other deciduous azalea species.

Prior to the current information on the ploidy of North American azaleas, Frank Mossman, John Thornton, Anthony Waterer Sr., and the authors all noted that certain species crossed much more easily in one direction than the other. In retrospect, these hybridizers noticed that diploids normally accept pollen from tetraploids whereas tetraploids normally reject pollen from diploids.

In 1972, Frank Mossman wrote the following concerning his hybridization with Rhododendron occidentale, a diploid:

"We have found that Rhododendron occidentale will cross with many other rhododendrons or azaleas if Rhododendron occidentale is the seed parent, but Rhododendron occidentale as a pollen parent produces few seed."

In 1974, Mossman added the following concerning his use of three diploid species as seed parents for pollen from occidentale:

"Rhododendron prunifolium, cumberlandense, or viscosum x Rhododendron occidentale will take."

Mossman stated concerning the work of Anthony Waterer Sr.:

"Anthony Waterer, Sr, of Knaphill Nursery, England, was the first known hybridizer of Rhododendron occidentale in the 1860's and reportedly had little success for almost ten years. It is probable that he had pollen only, at first, and later had flower-producing plants to use for seed parents. His effort with the Ghent Azaleas plus Rhododendron occidentale was the beginning of the Knaphill Azaleas and later the Exburys."

In the 1990's, we found 'Marydel' and 'My Mary' rejected pollen from late blooming deciduous azaleas such as R. arborescens, cumberlandense, flammeum, prunifolium, and viscosum but accepted pollen from each other and R. calendulaceum.

As an exception, John Thornton has found that Rhododendron austrinum normally rejects diploid pollen but was able to successfully cross Rhododendron canescens 'Crane Creek' onto Rhododendron austrinum on one occasion. The resulting seedlings were “sickly and sterile”. R. canescens 'Crane Creek' is a lab-tested diploid.

Mike Oliver cross raised by Dick Cavender’s of Rhododendron calendulaceum ‘Colossus’ X occidentale ‘SM-30’ and Jim Skonieczny's self of Rhododendron calendulaceum 'Colossus' X occidentale ‘SM-189’ are 2 possible additional exceptions of a tetraploid accepting pollen from a diploid. Augie Kehr was successful crossing an evergreen azalea onto Rhododendron calendulaceum 'Colossus'. Dick Jaynes in his work was only able to successfully cross evergreen azaleas onto diploids and not tetraploids. Carlson crossed luteum, a tetraploid, onto R. calendulaceum 'Colossus'. Britt Smith’s crossed of R. calendulaceum 'Colossus' onto occidentale, a diploid, producing at least some fertile offspring. We have found no documentation of a member of the tetraploid clade accepting pollen from Rhododendron calendulaceum 'Colossus'. What is interesting to us is that Rhododendron calendulaceum 'Colossus', believed to be a calendulaceum by David Leach, Augie Kehr, and Clarence Towe, behaves by the evidence above as a member of the diploid clade. In other words, our rules suggest, probably falsely, that R. calendulaceum 'Colossus' is more likely a R. cumberlandense. We have never used R. calendulaceum 'Colossus' in any of our crosses. 'Pumpkin 3.1416' is a Carlson cross of R. calendulaceum 'Colossus' X luteum.

Lab testing the ploidy of 'Colossus' would be informative; however, the more interesting question is how general is 'Colossus' in violating Rule #4 above. Are the crosses mentioned above repeatable? Does 'Colossus' accept pollen from most or all occidentale. This is doubtful since Frank Mossman used 'Colossus' only as the pollen parent in his hybridization program involving occidentale. Does 'Colossus' accept pollen from other diploid species besides occidentale? Does 'Colossus' accept pollen from tetraploids?

Frank Abbott of Saxtons River, Vermont produced 'Margaret Abbott' using prinophyllum, a diploid X calendulaceum, a tetraploid. In a personal letter from Joseph Gable written in the 1940’s, Frank was reminded to always put the seed parent first in listing the cross as this convention had not always been followed in the past and led to confusion.

Ron Rabideau of Rarefind Nursery grew 2 orange flowered seedlings from seed he collected from a native Rhododendron prinophyllum on his parents' property in Ashburnham, MA. This Rhododendron prinophyllum was growing near an orange Exbury azalea, most likely Rhododendron 'Gibraltar' which is a lab-tested tetraploid. This interaction provides support for the possibility of diploid X tetraploid occurring in nature. Tom Ranney and Clarence Towe have documented natural occurring triploids. T.G.R. Eeckhaut, L.W.H. Leus, A.C. De Raedt, and E.J. Van Bockstaele ploidy testing of Ghents showed a mixture of triploids and tetraploids.

Research by Ernest Henry Wilson and Alfred Rehder indicates that 3 of the earliest (1830) English deciduous hybrids where the pollen parent is known were each diploid X tetraploid, namely R. viscosum X luteum, flammeum X luteum, and periclymenoides X calendulaceum. In this timeframe many native deciduous species were grouped under viscosum and periclymenoides.

An examination of ARS seed exchange lists from 1990 to 2008 indicates that for crosses involving an azalea from each of 2 clades, the crosses where the diploid is the seed parent far out numbers those where the seed parent is the tetraploid. Moreover, most of these interclade crosses where the tetraploid is the seed parent, R. calendulaceum is listed as the seed parent. It is interesting to point out that Rhododendron cumberlandense, a diploid, is often misidentified even by experts as R. calendulaceum, a tetraploid.

Jukka Kallijarvi wrote the following in an email conversation comparing Azaleas to rose hybrids:

"Rules #3 and #4 are, in fact, a rule of thumb in rose hybridization. Pollen from tetraploids works on diploids, but not vice versa. Also, tetraploid roses are generally much easier to hybridize than diploids."

In 2008 we performed 18 tests using Rhododendron calendulaceum 'Cherokee', a tetraploid, as a seed parent. In each instance, pollen from the 5 different tetraploids produced seedpods. In each instance, pollen from the 13 different diploids failed to produce seedpods. In the same year, pollen from 12 of these diploids produced seedpods when applied to other diploids. In 2009 we placed pollen from R. colemanii and “pink austrinum”, both tetraploids, onto several tetraploids producing seedpods in each instance. In total over the years, we have done 50 crosses placing diploid pollen onto tetraploids and all have failed to produce seedpods.

In 2009, we performed 42 tests placing tetraploid pollen on fertile diploids. Forty of these crosses produced seedpods. Our experience indicates that, for the same diploid seed parent, pollen from a tetraploid produces larger seedpods than pollen from a diploid. In some cases, much larger seedpods result. Hans Eiberg states that the size of a seedpod is determined by the number of seeds and the amount of DNA in each seed so for a fixed number of seeds the seedpod would increase in size depending on whether the resulting seed was diploid, triploid, or tetraploid.

In 2009 we placed R. molle pollen on 8 diploids producing seedpods in each instance. Frank Abbott produced 'Jane Abbott' using R. prinophyllum X 'Miss Louisa Hunnewell' where 'Miss Louisa Hunnewell' is a cross between the Japanese and Chinese forms of molle. Ed Mezitt and Harold Pellett produced hybrids using R. prinophyllum X molle hybrids. Felix and Dijkhuis produced hybrids using R. viscosum X molle.

There are no documented interspecies crosses involving Rhododendron vaseyi. All of our attempts at crossing other species onto Rhododendron vaseyi have failed.

Caution about Historical Documentation

Tetraploid X diploid crosses of deciduous azaleas are mentioned in the literature. The reader when reviewing such crosses has to be mindful of three things:

1. Many deciduous azaleas documented as “natural hybrids” of tetraploid X diploid species are selections found in the wild. The parentage is based on the conjecture of knowing both the physical characteristics and the distribution of the species in the immediate area. Which species is the seed parent is unknown.

2. In the past, especially in the 19th century and early 20th century, the order of the parentage was alphabetical. The use of seed parent first and pollen parent second is now the accepted way of listing parentage of a cross.

3. Our native deciduous azaleas are often misidentified even by experts.

Labels at arboretums and display gardens can be wrong by benign neglect, malicious or helpful label switching, and incorrect identification by the initial source. In fact, an examination of Galle's wonderful tome, Azaleas shows that once natural hybrids are excluded and one discounts 'Galle's Choice', documented as R. calendulaceum X alabamense as very likely R. calendulaceum X colemanii, there is not a single occurrence of a documented cross of a tetraploid deciduous azalea species as the seed parent with the diploid native deciduous azalea species as the pollen parent.

Worthy of mention is that no matter how careful one performs the multiple steps involved in producing a named hybrid, including accurate identification of parents, proper hybridization techniques, proper seed handling, and proper labeling of seed, seedlings, and transplants, one unintentional mistake may result in an inaccurate documentation of the parentage. We believe that reproducibility, using multiple crosses on the same parent and the same pollen across many different parents, and the distribution of seeds to the seed exchanges will address some of these issues.

Home Tests for Ploidy

Prepare for hybridization the unopened flower buds from known tetraploid and known diploid deciduous azaleas by removing the corolla and immature stamens, then wait one to two days allowing their styles to straighten and stigmas to become receptive. For clarification the use of the terms pollen and seed fertile are based on prior experience. “Pollen fertile” refers to a deciduous azalea’s pollen that has been used previously to successfully produce seed from a hand crosses. “Seed fertile” refers to a deciduous azalea that has produced seed from either hand crosses or known to set open pollinated seed freely.

A deciduous azalea that accepts pollen from both diploids and tetraploids and, also, produces pollen that takes on both diploids and tetraploids is indeed rare.

Speculation is a fertile triploid would act similar to a tetraploid.

To increase confidence, perform both of these tests for multiple parents of known ploidy. For conclusive knowledge send the azalea to a lab for testing.

Pollen Parent Test

One can test the likely ploidy of a “pollen fertile” deciduous azalea as follows:

Place the pollen of the deciduous azalea of unknown ploidy onto known tetraploids and known diploids stigmas from the 2 clades mentioned above.

If the known tetraploid(s) X unknown ploidy produces seedpods, then the unknown is very likely a tetraploid.

If the known tetraploid(s) X unknown ploidy fails to produce seedpods but the known diploid(s) X unknown ploidy produces seedpods, then the unknown is very likely a diploid.

If no seedpods are produced for either known set of seed parents, then no conclusion is reached.

Seed Parent Test

One can test the likely ploidy of a “seed fertile” deciduous azalea as follows:

Place the pollen of known tetraploids and known diploids from the 2 clades mentioned above onto the deciduous azalea of unknown ploidy.

If the unknown ploidy X known diploid(s) produces seedpods, then the unknown is very likely a diploid.

If the unknown ploidy X known diploid(s) fails to produce seedpods but the unknown X tetraploid(s) produces seedpods, then the unknown is very likely a tetraploid.

If no seedpods are produced for either known set of pollen parents, then no conclusion is reached.

Conclusion

Hall's clade work and Ranney's ploidy work divides the deciduous azaleas into a 6 species tetraploid clade and an 11 species diploid clade where Rhododendron canadense, molle, and vaseyi are excluded. Their work caused a paradigm shift in how we think about our deciduous azaleas and how we approach doing hand crosses involving these azaleas. The rules of engagement address this shift in our thinking and have dramatically increased our ability to predict the possibility of producing seedpods.

Our evidence suggests that the ability to produce seedpods is clade dependent but is not species dependent with respect to the 2 clades. In other words, in general, species within a clade behave similarly with respect to accepting pollen from within the clade and between the 2 clades. All species within a given clade accept pollen from one another. All species in the tetraploid clade reject pollen from all the species in the diploid clade. All species in the diploid clade accept pollen from all the species in the tetraploid clade.

It is highly likely that individual plants exist, such as calendulaceum 'Colossus' and canescens 'Crane Creek', that fall outside these rules of engagement especially Rule #4 above. The questions are as follows:

Are the exceptions repeatable? Were viable offspring produced? Were fertile offspring produced?

Are there more such plants? How do such plants get identified and documented?

Are such plants associated with certain species?

What is the actual lab-tested ploidy of these plants? Are most such plants diploids, tetraploids, or possibly triploids?

Do such plants fall outside Rule #4 when crossed with only a few plants in the other clade, or for an entire species in the other clade, or for several or all the species in the other clade?

Notes and References

Rhododendron colemanii by Ben Hall, Tom Ranney, and Ron Miller

Ploidy Levels and Relative Genome Sizes of Diverse Species, Hybrids, and Cultivars of Rhododendron by Jones, Ranney, Lynch, and Krebs

Clade Ploidy of Deciduous Azaleas by John and Sally Perkins

Ploidy Research of Rhododendron canadense by John and Sally Perkins

Status of Ploidy Research for Rhododendron canadense by John and Sally Perkins

Dr. Tom Ranney is now testing the ploidy of living samples of Rhododendron canadense.

F1 Crosses of Evergreen and Deciduous Azaleas and Other Wide Crosses of Rhododendron by Richard A. Jaynes

With Camera, White Umbrella, and Tin Pants In Rhododendron occidentale Heartland by Frank Mossman

The Western Azalea, Rhododendron occidentale by Frank Mossman

ARS Seed Exchange Lists: 1990 to 2008

A Monograph of Azaleas: Rhododendron subgenus Anthodendron by Ernest Henry Wilson and Alfred Rehder

Rhododendron periclymenoides X calendulaceum

Lindley (in Bot. Reg. XVI. t. 1366 [1830]) states under A. calendulacea sub-
cuprea, quoting from Mr. Gowen's letter, that this form was raised at Highclere
between A. nudiflora rubescens impregnated with pollen of A. calendulacea
triumphans.

Rhododendron flammeum X luteum

In the Botanical Register Mr. Gowensays: "This Azalea was raised at Highclere
in the same year with those already figured in previous parts of this work and is
a seedling from Azalea coccinea major impregnated by the pollen of Azalea pontica.
The flowers are bright pink with the narrow lobes of R. nudiflorum and with the
upper lobe of a pale buff color or nearly whitish."

Rhododendron viscosum X luteum

Sweet states that he received the specimen figured the end of May, 1830, and that "the seeds were raised by Lord Carnarvon's gardener from Azalea viscosa var. rubescens, fertilized by A. pontica under Mr. Gowen's own inspection."

Rhododendron flammeum x molle.

The plant is stated to be "a hybrid produced from A. coccinea fertilized with the pollen of A. sinensis. The size of the flowers and the foliage with the entire habit of the plant is quite like that of the A. sinensis with the exception of the color which differs only in the light orange-red margin of the corolla." The hybrid was raised by Mr. Cunningham of Comely Bank near Edinburgh, in whose collection it flowered February, 1835. The parentage given is probably correct as far as can be judged from the colored plate.

Rhododendron arborescens x calendulaceum = R. Anneliesae (Rehder)

This hybrid originated accidentally at the Arnold Arboretum and was raised probably in 1896 from seed of R. calendulaceum or R. arborescens collected in the Arboretum. It is exactly intermediate between R. calendulaceum and R. arborescens and I have little doubt that it is a hybrid between these two species. The first flowers of R. arborescens are usually just beginning to open about the middle of June when late blooming forms of R. calendulaceum bear the last flowers; and with dichogamous plants this is just a favorable condition for cross-fertilization. From R. calendulaceum it differs chiefly in the glaucous and glabrous under side of the leaves, only the midrib being furnished with strigose hairs and slightly pubescent toward the base, in the very sparingly hairy branchlets and in the longer corolla-tube of the pinkish white fragrant flowers marked with a large yellow blotch and in the style puberulous only near the base. From R. arborescens it differs in the slightly pilose and slightly puberulous branchlets, glabrescent toward the base, in the pubescent and strigose midrib of the under side of theleaves, in the large yellow blotch on the upper lobe of the pinkish white flowers, in the shorter ovate calyx-lobes and in the style being puberulous near the base.

It is a shrub of vigorous habit, very handsome in flower with its large fragrant, pinkish white flowers marked with a conspicuous yellow blotch; the pinkish corolla-tube is rather densely furnished with short glandular hairs and the style is purple toward the apex. The leaves are elliptic or broadly elliptic and somewhat bluish green above.

R. Anneliesae is named for my wife.

Species in Our Mist by American Rhododendron Society Massachusetts Chapter Species Study Group

"A Revision of Rhododendron Section Pentanthera", Edinburgh Journal of Botany, Volume 50, No. 3 (1993) by Kron, Kathleen A.

KONSTRUKTION AF RHODODENDRONFAMILIENS STAMTRÆ by Hans Eiberg

Phylogenetic tree published by Hans Eiberg

Eiberg, Hans (1997) Rhododendronfamiliens stamtræ 2. Rhodo-Nyt 1: 14-18

Eiberg, Hans (1999) Rhododendronslægtens stamtræ. in Rhododendron i Danmark i 25 år page 186-199. Copenhagen.

"Occurrence of polyploidy in Rhododendron luteum Sweet, Hardy Ghent, and Rustica hybrids", Eeckhaut, T.G.R., L.W.H. Leus, A.C. De Raedt, and E.J. Van Bockstaele. 2004. The Azalean 26:32-37.

Sakai, K., Y. Ozaki, K. Ureshino, I. Miyajima, A. Wakana and H. Okubo.,"Interploid crossing overcomes plastome-genome incompatbility in intersubgeneric hybridization between evergreen and deciduous azaleas.",Scientia Hortic.,115: 268-274.,2008.02.

molle X 4x deciduous azaleas produce seed capsules whereas 4x deciduous azaleas X molle do not

We found in 2009 that the 4x 'Marydel' rejected molle pollen but we did no other such 4x X molle crosses. We found in 2010 that luteum rejects molle pollen.

George Woodward has found that tetraploid lepidotes reject pollen from diploid lepidotes but diploid lepidotes do accept pollen from tetraploid lepidotes.

Mike Creel wrote the following:

"I well-pollinated two different Mountain Flame Azaleas - 'Gamecock' and 'Walhalla Gold' - with fresh pollen from a nearby eastmanii this May, and NONE of the flowers formed a seed pod, acting like they had never been pollinated."

"Can anyone try to explain this apparent incompatibility between calendulaceum and eastmanii?"

"A friend of mine in Oregon has had several successes with crossing occidentale and eastmanii, so those species appear compatible."

Jim Barlup stated the following Barlup Lecture:

"This years 'Gargantua' seed was fertilized with four different tetraploid. They germinated and seedlings currently growing well. There were no results using the pollen of diploid. I am not a scientist and I do not know the answers to this curious puzzle. I am grateful that the plants do not know not read, so they know what they are supposed to do. All I know is the results."

We found using pollen testing in 2010 that our seedling of the Oliver / Cavender of Rhododendron calendulaceum ‘Colossus’ X occidentale ‘SM-30' is both seed and pollen fertile. Diploid pollen is accepted by this seedling indicating strongly but unconclusively that this seedling is a diploid.

We found using pollen testing in 2010 that our calendulaceum seedling from 'Engine Gap' behaves as a tetraploid.

We found in 2009 that canadense accepts pollen from both luteum and atlanticum.

Two reports of vaseyi crosses occurred in 2010.

Werner Brack crossed albrechtii X vaseyi creating a single seedpod about half the size of a typical pod of self pollination on albrechtii.

Tadeusz Dauksza crossed vaseyi X 'Western Lights' to produce seedpods. 'Western Lights' is a tetraploid produced by Briggs from 'Orchid Lights'.

To date with the exception of vaseyi which does not easily cross with other species the ploidy of every deciduous azalea species in the 2 ploidy based clades plus canadense and molle could have been accurately predicted using the home pollen test for ploidy.

Research showing kuisianum X molle produces triploid due to an unreduced gamete in the kiusianum seed parent

The research shows that a lab tested diploid kuisianum crossed by a lab tested
diploid molle produced a single triploid offspring. That diploid X diploid can
result in a triploid in one generation is a lab documented fact.

Seed Size

In both monocots and dicots, when the relative dosage of maternal and paternal genomes is perturbed, the endosperm and seed size are affected (13, 14). Arabidopsis, a diploid plant pollinated with tetraploid pollen, produces large seeds. This cross generates tetraploid endosperm (2 ♀:2 ♂) with paternal genome excess rather than the normal triploid endosperm produced by diploid parents. A different endosperm and seed result is generated when a tetraploid plant is pollinated with diploid pollen generating maternal genomic excess (4 ♀:1 ♂), and the pentaploid endosperm results in smaller seeds than normal. Apart from the ploidy level and parental genome representation, endosperm development is also subject to differential expression of many genes that depends on their parent of origin.

Endosperm Degeneration

The germination of pollen grains on the stigma and the growth of pollen tubes in the style and entry of pollen tubes into the micropyles in 4X×2X are in a fairly normal manner when compared with controls 2X×2X. The percentages of pollen tubes entering ovules of the crosses 4X×2X and the control 2X×2X had no significant difference. Fertilization was normal in cross pollinated ovules. The ovules of 2X×2X,4X×4X,4X×2X were studied to determine the sequence of events leading to embryo and endosperm deterioration in 4X×2X ovules. On the 3rd day after pollination, the 4X×2X showed no signs of abnormality, Endosperm deterioration was the first indication of anatomical abnormality. The endosperm was disintegrated totally by the 7th day after pollination. Deterioration of both the 4X×2X embryo and the cells of proliferated endothelium was complete by 23 days. Therefore it might be concluded that the sterility of crosses between diploid and tetraploid was primarily attributed to the abortion of hybrid endosperm.

Frank Mossman's Occidentale Slideshow

This slideshow includes images of calendulaceum 'Colossus', occidentale SM-30, occidentale SM-189, and occidentale X calendulaceum 'Colossus'

Rhododendron 'Moorgold' from seed of 'Daviesii' a lab tested triploid.

Henry Skinner x 'Daviesii'

We have succesfully crossed tetraploids onto viscosephalum which is a similar cross to 'Daviesii'.

'Canobie Sunset' X luteum set full seedpods for all pistils. 'Canobie Sunset' is an evergreen azalea.

Pollination by Marc Colombel

In Search of Native Azaleas: Henry Skinner's 1951 Southern Collecting Trip

American Azaleas by Clarence Towe

Azaleas by Fred Galle

Frank Abbott's Village of Azaleas by John and Sally Perkins

Azalea Society of America

cumberlandense X luteum

Burce Clyburn reports the the image titled luteum X cumberlandense on the Azalea Society site is from seed Bruce received as bakeri X luteum.

The American Rhododendron Society

Rules of Engagement

Have Gun - Will Travel