|SOME THOUGHTS ON ALBESCENT CYMBIDIUMS. |
Cymbidiums which are genetically incapable of normal anthocyanin pigment
production have been the source of much interest and attraction; particularly
in the last few decades.The question of a suitable name for plants of this this
type has been long debated and there are many suggestions. Albescent and Albinistic refer to plants which show a significant degree of reduction in normal
anthocyanin production. I tend to use the former term, but not exclusively. Albino is often used for anthocyanin-free plants, but to me this term means plants
incapable of producing chlorophyll; that is those with white leaves. A selfing
of Cymbidium suavissimum has given me about 25% of seedlings of this type, not something I have
attempted to maintain in cultivation; the normal green seedlings being
difficult enough. Alba is a useful term for anthocyanin-free plants, especially where cattleyas are
concerned; most alba cattleyas being white. Unfortunately many alba cymbidiums are green. I still find this the term of choice for plants which
have no anthocyanin. Pure-colour is currently the most popular term to describe anthocyanin-free cymbidiums.
Nice clean pinks with no browning seem to fit better with this name, in my
opinion. Concolor refers to plants having the lip similarly coloured to the tepals and are not
necessarily anthocyanin deficient. A Tinted Alba, by my definition, is a plant which contains a highly reduced anthocyanin
concentration, but is not completely anthocyanin-free. I would like a useful
term like Ananthocyanic to exist, but it really does sound rather pedantic.
Gregor Mendel was the father of genetics, but he died before his child could be born. Sixteen years after his death, his work was rediscovered. The year was 1900, and for two or three years before this, an Englishman, C.C. Hurst, had been studying the inheritance of flower colour in Cattleya. When Mendel's hypotheses surfaced, Hurst was in a position to become the first person to view the genetics of orchids with a scientific eye. He did much work on the alba clones of Cattleya and his C and R lists have become well-known to generations of orchid people, but he did not work on the genus Cymbidium to any extent.
The first person to look at the genetics of Cymbidium in any depth appears to have been Gustav Mehlquist, who published the landmark article "The Ancestors of our Present-day Cymbidiums" in the Missouri Botanical Gardens Bulletin, 34: 1-26, in 1946. (This article is more readily accessible to cymbidium growers as a reprint published in the Orchid Advocate, 8(1): 13-18 and 8(2): 48-52 in 1981.) In this article, Mehlquist started the list of albescent Cymbidium hybrids. He went on to do critical work on the cytogenetics of cymbidiums, establishing the existence of polyploidy in Cymbidium and is thus one of the fathers of the polyploid revolution in cymbidium breeding; Donald Wimber being the other.
Lee Lenz and Donald Wimber, contributing the chapter on "Hybridization and Inheritance" in Carl Withner's 1959 book The Orchids - A Scientific Survey, expanded Mehlquist's list. Up to this point, these albescent clones of Cymbidium were known as "concolors". Don Wimber went on to do the very important work of doubling chromosome numbers with colchicine, giving us new polyploid studs with which to breed.
Paul Gripp also addressed albescent cymbidiums, in one of a remarkable flurry of articles mostly concerning cymbidiums, published in the American Orchid Society Bulletin from 1964 onwards and only slowing down after 1970. His article "Concolor and Recessive-colored Cymbidiums" appeared in the A.O.S. Bulletin, 37: 192-199, of 1968. In this article, Paul divided the albescent plants that he knew at the time into three groups. Aside from those plants mentioned above, and others which had passed through his hands as a foremost grower, he included those brought to his attention by Alvin Bryant, then working dedicatedly on alba cymbidiums in Australia.
The first of Paul's categories was "Concolors" (lip devoid of marking or suffusion) and included some true alba clones. The second category was "Suspected recessively marked lips or albino cymbidiums" and included, of interest with regard to this article, Cym. Eburneo-lowianum 'Concolor' and Cym. eburneum. The third category was "Concolors in miniature cymbidiums".
From 1972, Alvin Bryant wrote articles on the Australian experience of albescent cymbidiums. While previous students of alba cymbidiums had only made presumptions with regard to the genetics of this group (based on Hurst's work with cattleyas), Alvin laid a good scientific groundwork. Although one thinks of the 'Sleeping' series of Cymbidium hybrids as an invention of Valley Orchids, the first few plants with this name were in fact registered by Alvin Bryant. Alvin's terms for alba cymbidiums were 'non-staining' and 'albino'. The term 'pure-colour' appears to have been the invention of either Bob Vandyke or Merv Dunn, both associated with Valley Orchids of Australia, dating back to 1970.
In the Cymbidium Society News, 27: 140-146 from 1972, Jim Burkey catalogued the alba clones in an article "A Listing of Alba Cymbidiums". He repeated Paul Gripp's assertion that Cym. Eburneo-lowianum 'Concolor' and Cym. eburneum were alba clones but qualified the latter with "pure white form". Jim also addressed the question of how these clones should be defined and named.
Andy Easton has also briefly covered albescent cymbidiums on many occasions. In his article "About Albas and Allotetraploids" published in the Orchid Advocate, 1(6): 212-214 (1975) Andy says the following; "Although it is periodically debated, an alba form of C. eburneum definitely exists. There is an interesting hybrid of Gottianum with Durham Castle that produced some albas that were also concolors. They resembled C. eburneum in form and spike habit and were pure white all over. Charming! And C. Alexanderi 'Album' FCC RHS from the 1911 crossing of Eburneo-lowianum 'Concolor' with C. insigne 'Westonbirt', a concolor carrying an alba gene, shows strong evidence of an alba eburneum grandparent."
Having read everything I could get my hands on regarding cymbidiums, I was at one point quite satisfied that Cym. Eburneo-lowianum 'Concolor' was an alba and that there was an alba form of Cym. eburneum. Checking the award citation for the FCC/RHS that Cym. Eburneo-lowianum 'Concolor' received on March 24, 1903, however, clouded the situation. It said the following: "Flowers large, yellowish cream colour, with purplish markings on the front of the lip." (Journal R.H.S., 28: lxxxi). In the same journal (26: 922), Cym. Eburneo-lowianum 'Mureauense' was described as follows; "Raised by M. C. Vive of Mureaux (Seine et Oise), France, out of Cym. lowianum 'Concolor' by Cym. eburneum. Segments of the flowers cream-white, lip narrowly margined with purple; the peculiar yellow tint of the flower recalls that of Cym. lowianum 'Concolor'." So, in fact, these early Cym. Eburneo-lowianum plants were not albas, but were distinct from the original plants made with normal Cym. lowianum. It is not impossible that the early albescent Cym. Eburneo-lowianum was selfed or sib-pollinated, giving rise to true alba plants which survived well into the twentieth century. I must also mention at this point, that it is probable that Cym. Veitchii is the correct name for Cym. Eburneo-lowianum, as it has precedence. I will, however, be using the latter name as it is the one more commonly used. (P.S. The International Orchid Registrar has informed me that in the case of horticultural plant names, precedence is not absolute, and more widely used names can be accepted, with the earlier names being 'supressed'.)
Being interested more in cymbidiums exhibiting the charm of the species, rather than those producing great, big heaps of floral tissue, I have remade many primary hybrids including both versions of Cym. Eburneo-lowianum, and those made with Cym. lowianum 'Concolor' are distinct. My photo of the two versions together shows the differences in tepal colour, as well as the striking differences in lip-pigmentation. The 'Concolor' version has less lip area pigmented, the markings being a distinct light orange-brown, and this pigment fades rapidly in our hot, bright spring. Within two weeks the lip appears to be 'concolor'. From this pair of plants alone it is rather difficult to explain what is going on here, from a genetic point of view.
Two clones of Cymbidium Eburneo-lowianum from two different crosses. The spike on the left comes from the cross Cymbidium lowianum 'Concolor' x Cymbidium eburneum 'Santa Barbara'; that on the right is a cross between a normal, anthocyanin-containing Cymbidium lowianum x C. eburneum.
Another picture of the albescent Cymbidium Eburneo-lowianum, showing more clearly the trace of orangy-brown pigment present in the lips and under the columns of newly-opened flowers.
I have, however, been extremely fortunate to bloom another cross which has helped me better understand the genetics involved. A cross between Cym. Cooperi 'Plush' (a plant I believe to be nothing more than an excellent, perhaps slightly introgressed form of Cym. insigne, and about which I will write in the future) and a Cym. eburneum has recently started flowering for me. These Cym. "Gottianum" plants fall into two groups. The first group has light pink flowers with the lip marked with medium-purple dots and dashes. Plants of the second group open pure white and the lip-markings are of a noticeably paler colour, but still exhibit some anthocyanin colouration. The latter I call my 'tinted-alba Gottianums'. Knowing from previous experience that Cym. Cooperi 'Plush' carries an alba gene, something that has been reported in the Orchid Advocate a while ago (see 18(2): 58-59 of 1992), an explanation for these two groups of progeny can be suggested. I have included a photo showing the flowers of one plant of each group.
Two clones from the cross Cymbidium Cooperi 'Plush' x Cymbidium eburneum 'Santa Barbara', that on the left having normal colour, while the right-hand one has a reduced anthocyanin content.
It seems clear to me that more than two different alleles exist for the alba
gene in Cymbidium. In the article "Floral Pigments in Cymbidium" (CSN 27(4): 170-171) the authors Strauss & Arditti use the letter c to refer to genes at this locus and c is classically the letter used throughout genetics for genes related to
pigment deficiency. So here I will define my three alleles as:
|C (upper case)||the dominant normal (coloured) gene|
|c (lower case)||the recessive alba gene|
|c t||an allele allowing limited pigment expression|
|Cym. lowianum 'Concolor'||c c (a true alba clone)|
|Cym. eburneum||c tc t(a tinted alba)|
|Cym. Cooperi 'Plush'||C c (normal coloured carrying alba)|
Cymbidium Eburneo-lowianum - plate 6 in James O'Brien's book Orchids. This photograph was taken of a plant from the Westonbirt Collection of Sir George Holford (grower, Mr. H. G. Alexander).
The peculiar lip-colour of the Cym. i'ansonii seen in cultivation does not appear to be caused by a gene that would be an allele in this series;
based on the fact that a hybrid of this species with Cym. Cooperi 'Plush' did not segregate into two colour populations; all plants
having normal lip colouration.
Of the other Subgenus Cyperorchis species, it is probable that Cym. mastersii carries predominantly the tinted alba gene (except for plants which belong to the formerly recognised var. affine, which exhibits good lip colour), and it is possible that Cym. roseum and even Cym. elegans could do so as well.
Amongst the miniature species, Cym. floribundum (pumilum) var. album is definitely a tinted alba, but as the genome of this species is not particularly homologous with that of the large species, it is difficult to state categorically that the same allele, namely c t, is involved. The alba clones of Cym. ensifolium and Cym. sinense appear to be true albas, based on breeding results, but once again non-homology clouds the issue. Cymbidium madidum is another species which exhibits albescence and warrants examination.
Plants like Cym. Balkis 'Solent Queen', Cym. Nadina 'Concolor', Cym. Amy Stewart 'Zita' etc. with small, concolor lips, represent hybrids exhibiting the c t gene phenotypically, and you will find Cym. eburneum on both sides in their ancestry. Suffusions on a clear lip, such as may be seen in Cym. Mem. S.G. Alexander FCC and Cym. Narela 'Jennifer Gail' may represent phenotypic c t lips on top of a contribution by Cym. sanderae. The complexity of the genetics of lip-markings is probably a huge subject and when one considers tetraploids with four genes at each locus, the complexity compounds considerably.
Additionally, it is quite possible that more than three alleles may exist in the alba series in Cymbidium. In the domestic cat, the albino series of alleles, also denoted by the letter c, includes five alleles; normal colour, burmese, siamese, blue-eyed albino and pink-eyed albino.
As far as I am aware, this is the first time that "tinted alba" has been considered from a genetic point of view and the first time that the idea of a third allele in the alba series in Cymbidium has been entertained. We are on the verge of knowing about the DNA of cymbidiums when we barely have any concept of what genes our beloved flowers hide beneath their elegant surfaces. Grow, observe and ponder over your cymbidiums, particularly species and species hybrids and help to reveal a little about their genetics. Every small contribution, like this one, will help us to understand our plants more.
© 2003-2011 Greig Russell
This page was updated on 11th May 2009.