Facts and Fancies
David G. Leach, Brookville, Pa.
When friend Guy Nearing concluded our discussion on breeding rhododendrons in the April, 1953 issue of
The Quarterly Bulletin of the American Rhododendron Society
he misquoted me grossly, but gentlemanly restraint and generous impulse combined for me to forgive him privately instead of castigating him publicly. (For the record, I do not advocate inbreeding a variable species such as
, before crossing it with another species. This problem of heterozygosis is easily solved by growing more seedlings than usual of the primary cross.)
Now we have a clarion call from the wilderness in the form of an article from another quarter entitled "Theory and Practice," which was published in the January, 1954 issue of The Quarterly Bulletin of the American Rhododendron Society . With an uneasy, sidelong glance the captious author says "I have no intention of entering into a breeding debate with Mr. Leach..." But alas, I feel impelled to take up the challenge, secure now in the knowledge that I am not overly tempted by the lure of the last word.
So...to the battlements, readers! And bring your copies of the January issue. In the article by my new critic which appeared in that issue Dr. Clement Bowers is blamed for the 3-star rating of R. (hybrid) 'Meadowbrook' as it was given in "The Rhododendron Yearbook for 1945." I had cited my critic's praise of this cultivar as the best known example to prove that cross breeding Catawba hybrids can yield good results. But he says now that R. (hybrid) 'Meadowbrook' is of very inferior quality. Although my new found opponent assigned some quality ratings himself he makes it clear that he included the Bowers rating without protest or comment despite his strong disagreement; in fact, we are given to understand that, while holding a low opinion of R. (hybrid) 'Meadowbrook' he nevertheless added gratuitously to Dr. Bowers' 3-star rating, his own judgment of "very fine, vigorous." Out of the entire list of about 150 hybrids, which includes some of the best rhododendrons in existence anywhere, only four other cultivars are praised as "very fine" by my critic. Therefore, if the erroneous impression prevails that R. (hybrid) 'Meadowbrook' is a superior rhododendron, he has only himself to blame.
But I am content to conclude charitably that the capricious critic has changed his mind about R. (hybrid) 'Meadowbrook.' My case is secure on the evidence of the Shammarello seedlings that the crossing of Catawba hybrids can yield good results. Mr. Shammarello's seedlings No. A-1-P is the finest hardy rhododendron with a pyramidal truss of Waterer's ideal type that I have yet seen. The large, thick textured flowers are the lovely salmon pink of R. (hybrid) 'Corona.' The plant is vigorous and sturdy, and well furnished with large, dark green leaves. The best white flowered Shammarello seedling, of the same type, with built-up truss, is No. A-I-W. The ivory blossoms are fully four inches across, with a gold bronze blotch, and they are formed into tall, imposing trusses which bring to mind an improved R. (hybrid) 'Mrs. P. D. Wilhams'. Mr. Shammarello also has some outstanding red flowered rhododendrons. And all of these hybrids were produced from crosses among the standard commercial Catawba cultivars. I think it is not the best and most efficient way to breed rhododendrons. A lot of experimenting is needed to determine the combinations that "click." But my critic's contention that such matings can not possibly yield good results is a triumph of hope over fact.
The cross of 'Atrosanguineum' x griersonianum was cited in disproof of my proposal that there must be a hardy heritage from one parent and at least a semi-hardy element in the other for the seedlings to be as cold resistant as are the standard Catawba hybrids. A more unfortunate example could scarcely have been chosen. This is the cross of which R. (hybrid) 'William Montgomery' is the best known seedling. With the possible exception of Long Island, it is not hardy north of the Mason and Dixon Line and I am sure that Mr. Gable would not claim that any of the seedlings from this mating are as hardy as are the commercial Catawba cultivars.
Whirling like a dervish, my critic then attempts to disprove my analysis of the reason for the success of the Ridgewood hybrids ( griffithianum x decorum crossed with Catawba hybrids) by stating that catawbiense x decorum is not hardy under eastern conditions. Again, he could scarcely have chosen a more unfortunate example. Catawbiense album var. 'Glass' x decorum has been perfectly hardy in my arctic mountain climate where the temperature goes routinely to 20 or 25 degrees below zero in any normal winter. The reciprocal cross, decorum x catawbiense album var. 'Glass' produced for Mr. Joseph Gable his superb hardy white flowered cultivar which he named 'Mrs. Powell Glass'.
There follows then in my adversary's dissertation a bit of bald buncombe which takes its logic entirely from a misconception about a supposed "split-up" in the genes for hardiness which are assumed to co-exist in the Catawaba cultivars serving as parents of the Ridgewood hybrids. Their co-existence in a manner which would support this argument is a false assumption and I think it should be pointed out that merely to repeat a statement continuously does not make it fact.
That such rhododendrons as the hybrids 'Charles Dickens', 'Kettledrum', and 'Atrosanguineum' are able to endure extremely low temperatures is strong evidence that transgressive segregation accounts for such hardiness. This follows because we know that hardiness is not inherited as a simple dominant or a simple recessive. It is controlled by many genes and the usual result of mating a hardy species with a tender one is intermediate, half-hardy progeny. The logical explanation for these cultivars is that they are F 2 or advanced generation segregates of the original cross between tender and hardy rhododendrons and the behavior of their progeny also suggests that transgressive segregation is the reason for their cold resistance. The genetic "split-up" is a favorite over-simplification of those who are striving to bend theory to support faulty observation.
It seems to me that my opponent goes off the deep end when he asks why the Ridgewood hybrids are much hardier than catawbiense x decorum . They are not. I believe I am correct in saying that I have tested a wider variety of the Ridgewood hybrids under more severe conditions than any one else. It is my observation that catawbiense x decorum is hardier than are the siblings of R. (hybrid) 'Beatrice Pierce' and its sister seedlings H-46-6, which my critic mentions. But even if it were not, the point is immaterial. If the same plant of R. decorum had been used as the progenitor for both R. (hybrid) 'Beatrice Pierce' and the cross with R. catawbiense , the question would be germane. My critic obviously confuses a phaenotype with a genotype but readers will immediately recognize that different parents seldom produce identical children, and the progeny of plant "A" may be far different from the offspring of plant "B" even though both belong to the same species and are similar in outward appearance.
My adversary's article seems to me to be overflowing with false assumptions on which he then proceeds to elaborate plausibly. His questions give the appearance of one who has failed to understand the most simple and fundamental principles of heredity, as when he demands to know "what happens in these crosses ( R. catawbiense album var. 'Glass' x ( fortunei x campylocarpum )) to the tender genes of R. campylocarpum ...or are we to believe that these genes have suddenly become recessive and will not appear in any progeny?" I had proposed catawbiense album var. 'Glass' x ( fortunei x campylocarpum ) as the quickest and easiest way to obtain hardy rhododendrons with pale yellow flowers.
The hybrid which constitutes one side of this cross is R. fortunei x R. campylocarpum . It contains the genes for fortunei and it contains those from campylocarpum . The R. fortunei set lie in chromosomes paired with their opposite numbers from R. campylocarpum . Before this hybrid produces pollen, reduction division takes place so that the haploid chromosome number is restored in the pollen nuclei and only one chromosome of each pair enters each germ-cell. At this point many different sorts of germinal cells are produced containing genes representing an infinite number of combinations of the characteristics of the two species. Barring linkages, almost any combination of characteristics can be obtained if a large enough number of pollen cell nuclei are utilized. In the cross I proposed, R. catawbiense album var. 'Glass' x ( R. fortunei x R. campylocarpum ), a gamete is sought which contains the R. fortunei genes for hardiness and flower size in combination with the campylocarpum genes for yellow color. When one so constituted fertilizes an ovule of R. catawbiense album var. 'Glass' the resulting zygote will produce a plant which bears, as I asserted, "pale yellow blossoms in size half way between those of catawbiense and of R. fortunei ." Since my critic infers to himself a technical competence in his article, it is astonishing for him to demand what happens to the tender genes of R. campylocarpum . They are, of course, bestowed upon plants other than those which are the hybridists' goal, and such tender plants are eliminated by the rigors of winter weather in the East. Similarly, the genes for small flowers and for blossoms other than yellow are concentrated in other plants from the cross which become discards for this reason.
My opponent remarks "...have yellow and orange (colored flowers) suddenly become dominant?" He must go back and do his homework before pursuing further this matter, too. Yellow can dominate other colors in varying degree as witness R. (hybrid) 'Butterfly', which is a cross between campylocarpum and an old-fashioned wine red cultivar called R. 'Mrs. Milner'. R. (campylocarpum elatum x fortunei ) 'Letty Edwards'; R. (discolor x wardii) 'Inamorata'; and R. (fortunei x 'Goldsworth Yellow') 'Goldfort' are additional examples of crosses which refute my critic's claim that yellow has been "heretofore recessive."
My opponent says that "we do not know very much about the behavior of R. catawbiense var. 'Glass' in hybrid form (sic)." Actually, we know more about R. catawbiense album var. 'Glass' in inheritance than about almost any other rhododendron hardy in the East. In addition to innumerable crosses, Mr. Joseph Gable has raised plants of this species variety by the hundreds-perhaps by the thousands and he has stated repeatedly that when crossed under controlled conditions, it comes "true" from seeds. That can mean but one thing: the white is a homozygous recessive, in the lights of its inheritance in this and other instances, and it can not impart a magenta tinge to its progeny.
My new found critic seems not to have considered that his other parents could have, and did, provide the purplish tint of which he complains in the seedlings of his crosses. And he is very foolish to reject the seedlings of the several crosses which he proposes to discard for this reason. They provide the means to attain his goal in the next generation.
My adversary imputes a statement to me which I did not make when he says that in my proposed crosses I expect "the seedlings as a whole would carry all these good qualities." I made no such claim for the type of cross represented by the catawbiense album var. 'Glass' x ( fortunei x campylocarpum ). But I am amused because it was previously denied that any of the seedlings could represent a successful effort and in this instance he complains because all of the seedlings are not uniformly up to the ideal result. My opponent is a man of simple tastes; all he wants is the best of everything.
By the omission of a most critical portion of the passage, my meaning was distorted in a quotation of my comments on the type of cross represented by the formula, ( dichroanthum x griersonianum ) x ( griffithianum x catawbiense ). This cross had previously been proposed as a promising prospect for eastern breeders. The claim was made that if it exhibited the worst qualities of all four species in the progeny then some seedlings must also exhibit the best features in them. In refuting this contention I pointed out the patent absurdity of expecting desirable recessive qualities to be exhibited among the seedlings bred from such a formula. Such a cross simply can not result in a redistribution of all characters, or even a majority of them. The situation is somewhat complicated by linkages, especially sex-linked characters, but basically the attributes of plants are inherited in only three ways: in a dominant manner, in an intermediate fashion, or in a recessive way. I wrote: "Except for dominant qualities the formula presents no opportunity for the appearance of any but characteristics roughly intermediate between the two parents and/or the four grandparents. IN THIS RESPECT it is similar in result to a cross between two species." The italicized portion of my comment was omitted in the quotation, the confused author having missed the point of the passage cited. I maintained in effect that this formula could only yield seedlings exhibiting those qualities of their progenitors which were inherited in a dominant or in an intermediate quantitative manner. Put another way, I refuted the proposal that the seedlings could show any great range of characteristics inherited in a recessive manner. In disputing this statement my contentious contestant is obliged to take the unfortunate position that the progeny of such a cross will exhibit a general appearance determined by recessive characteristics. In the interaction of genes in complex crosses, characters inherited as dominants and intermediates (which are often undesirable) can and do create some variation among the seedlings, but this does not invalidate my statement.
Just why an unidentified inquirer at a British panel discussion is cited as an authority on breeding rhododendrons is incomprehensible to me, but in any case the same repetitious issue has been discussed earlier in this rebuttal.
Equally incomprehensible is a reference to Mr. J. G. Millais, who was no authority on breeding rhododendrons; and even more odd, the quotation used is contrary to my critic's own position that the consequence of breeding complicated hybrids is, to use his phrase, "junk." In the passage cited, a celebrated Dutch breeder describes this same procedure as a great success. In any case, as most rhododendron students know, Millais' works are full of misinformation and inaccuracies. As I write this article in mid-February I have for review an advance copy of Mr. Frederick Street's fine new book, "Hardy Rhododendrons" in which he describes Millais as "notoriously unreliable," and that is putting it charitably.
My opponent says that he holds me in the highest esteem and I trust readers will understand while I am beating him vigorously about the head that I esteem him highly too. I disagree with almost every word he writes. He is entitled to his views but his position appears to be capricious and contradictory, a result of having misconstrued the principles of genetics which he seeks to use to support his statements.