A New Direction For Hybridists
Fred E. Knapp, Locust Valley, N. Y.
Reprinted from the New York Chapter Newsletter
For its November meeting at Planting Fields Arboretum, the New York Chapter had a most unusual speaker, Dr. Harold Smith of the A. E. C. at nearby Brookhaven Laboratories. Dr. Smith, who has recently "made" the local press, "Time Magazine," and even we understand the BBC-TV on a recent European trip, brought a treat and a treatment to our group - a treat in that he is a very human and approachable scientist, and a treatment in that his subject was undeniably more scientific than our usual.
If the name Harold Smith is not known to you now, it may well be in the future. Dr. Smith and others at Brookhaven have succeeded in directly combining two species of tobacco by non-sexual means. His work is with somatic (body) cells. In very brief outline, it consists of breaking down the cell walls, fusing the wall-less cells directly into new cells, and growing plants from these combined cells. This last stage is analogous to the current tissue-culture reproduction process for asexual clonal propagation.
The plants so obtained are true hybrids, with certain differences from the hybrids which might be obtained sexually. The fusion of the cells is an addition process retaining all of the genetic material from both parents, rather than the usual selective pairing process which leaves some behind. As a result, it offers a chance of concentrating desirable genetic factors (or undesirable, of course), of bypassing certain apparent "rules" (such as the seeming antipathy in our genus of the genetic factors for true bright red and for northeastern style hardiness), of combining species with widely differing chromosome numbers normally reluctant to cross, and of obtaining fertile hybrids from crosses hitherto known as dead-ends.
All of this will not happen easily or quickly, but the possibilities are unbelievably wide, and tailor made for the genus rhododendron, with so many "impossible" crosses crying to be made.. And, of course, even one success produces a pollen source which could initiate a whole new wave of possibilities by conventional sexual propagation.
Another interesting potential of somatic cell fusion is the possibility of selection for specific purposes at the tissue-culture stage. While the new cells are still plated out in Petrie dishes of nutrient, (analogous to "lining out" our rooted cuttings), they can be subjected to stress in order to select the more suitable ones. This stress could be low temperature, high pH, viral influences, pollutants - and presumably the last living cells at some level of stress might produce correspondingly hardier plants, plants not requiring such acid soils, Phytophthora resistant plants, better parkway or city plants, etc.
Our program chairman, Dennis Stewart introduced Dr. Smith, an alumnus of Rutgers and Harvard Universities and a man who has rooted his own rhododendron cuttings and grown them on in his own yard, with some comments about Buck Rogers coming true in our time and a reference to such plants as "rhodolex" or "ilerho".
Dr. Smith did not emphasize this kind of goal in his lecture, but did not really deny it either. There appears to be no reason, other than a great deal of research and laboratory trial and error, why many inter-generic crosses cannot eventually be made! Some of the most unlikely sounding crosses may not be the most difficult when cell structure and nutrient requirements are examined. Dr. Smith's current project is to cross petunias with tobacco-ancient relatives though far removed in their present form.
After that - who knows? I should like to own the first rhodolex, let's say a bright red rhododendron truss or Ilex aquifolium 'Camelliaefolia,' with much larger leaves and berries! Or similarly, R. 'Crest' on I. a. 'Fructu-luteo'! But perhaps we should take care what we do in this area - lest one day we be swamped by commercial opportunists producing so many new plants as to obscure totally the plant world we know today. I think after I get my rhodolex we should stop! Or certainly after I have a kalmiodendron.
Regardless of speculations light or serious, Dr. Smith presented an interesting talk on what may be the most important new tool in horticulture in our time. Let us hope to use it as well as he described it, and if the day comes, to restrain such selfish feelings as I expressed at the end of the previous paragraph.