28 JOHN W. DUFFIELD 



have, and will continue to have a lot of diversity in your forest. If 

 you handle this right hopefully you will maintain and broaden this type 

 of diversity. You can do this through your selective cuttings to improve 

 the type of product that you get. I'd like to interject another point-- 

 that you shouldn't breed only for rust resistance. This is a mistake 

 that is made time and again. I have seen many plant breeders in my close 

 fraternity in wheat that have spent a life time developing disease resis- 

 tant varieties that have no value whatsoever because they don't yield. 



SLINKARD: Dr. Duffield, referring to your proposal for a wide gene 

 base within ecotypes, the phrase "within ecotypes" bothers me. I would 

 like to get your comments, or someone else's, on the use of wide adapta- 

 tion. In other words, instead of trying to get rust resistant selections 

 for each ecotype, why not try to combine ecotypes and get a wide range of 

 genetic variation so that one population may be adapted to a 2- or 3- 

 thousand feet altitude range or some other ecotypic variation? 



DUFFIELD: Well, I think that there are precedents that would 

 encourage us to hope that this might be possible. We have evidence on 

 both sides of this question. We have the evidence which I have referred 

 to very briefly on localized ecotypes and then we have certain species 

 which are notorious as being widely adapted, for example the Rocky Mountain 

 form of Abies concolor (Gord. $ Glend.) Lindl . , which you find cultivated 

 everywhere. Then there is the tree that grew in Brooklyn, Ailanthus 

 altissima (Mill.) Swingle. I would hope that we could develop similar 

 forms. Further, Jens Clausen and the Carnegie Instition group at 

 Stanford, working with altitudinal ecotypes of Fotentilla, were able to 

 develop F2 lines of extremely wide adaptability and good growth. 

 Developing wide adaptability appears to be very much in the cards. 



BORLAUG: One mere comment about this adaptation, because I think it 

 is fundamental to your long-time improvement. Again it calls for a 

 practical point of view. You can get specificity and you can maintain it, 

 but how are you going to use it? How are your seed programs going to be 

 handled so that you exploit this specific adaptation? This has come up 

 in recent years in cereal crop improvement. In Mexico we are aware of 

 and trying to get ecotypes for a lot of small niches in the mountainous 

 country. We gave it up and started over. Without going into detail, 

 the new work involved growing part or all of the segregating populations 

 at sea level and at 8500 feet, at 28 degrees latitude. The next genera- 

 tion was grown at 18 degrees latitude; and all those populations that 

 didn't do well under both sets of conditions, including severe disease 

 epidemics, were discarded. Sum and substance of all this has been that 

 after 15 or 20 years these varieties have provoked the so-called "green 

 revolution". Genotypes are those coming from that program in Mexico. It 

 also became apparent that one single gene and some modifiers has been 

 responsible for making it impossible to adapt any of the spring wheat 

 varieties bred in Canada or the northern U.S.A. to places below 38° 

 latitude. The Mexican varieties, however, will compete and in many cases 

 outyield Winnipeg varieties under Winnipeg conditions. I say, be careful 

 about specific adaptation. I recognize, however, since I did have a 

 forestry background many years ago, that this whole question of winter 

 tolerance, freezing and wintering is something that's not necessarily a 

 problem in an escape variety such as spring wheat. 



