Referring to Pierre Cronjé message on genotype X nutritional environment interaction [5 July]

One is left with the impression that biotechnology will solve the problems of the world and, in particular, plant or animal breeding. A common viewpoint of a biotechnologist is that of a reductionist, i.e. everything can be reduced to simple parts and the whole can be explained from the parts. Or, in this case, the reductionist would say that the phenotype, and all it's interactions with the environment, can be explained by studying individual genes controlling expression. To a certain extent this is true but it is much like saying that because we understand the atom we can predict the behavior of all material made from atoms. Another analogy is micro vs. macro economics. Which is better for predicting economic growth of a country?

The opposite of reductionism is holism: "The theory that living matter or reality is made up of organic or unified wholes that are greater than the simple sum of their parts" ( Third Edition copyright © 1992 by Houghton Mifflin Company). A holistic scientist is more of a statistician working with large sample theory (the central limit theorem) or asymptotic theory and it works quite well in animal breeding. Broilers only a few decades ago took 18 weeks to reach market weight, now they reach that weight in 6.5 weeks and with much improved feed efficiency. This improvement was possible without biotechnology and continues to be possible.

The point I am trying to make is that biotechnology (functional genomics) will certainly help us understand gene interactions and will have profound impacts on pharmaceuticals, health and well-being. However, the notion that it should be used for all, or even most, aspects of breeding is misplaced trust. High tech does not necessarily equate with good tech. Good tech is that which is cost effective and appropriate for the situation. For example, simulations (Muir, W.M. 1999. Molecular Genetics in Poultry Breeding. Proc. International Symposium on Animal Breeding and Genetics.. Eds. Lopes P.S, Euclydes RC, Torres RA, and Guimaraes, EF. pp 243-268) have shown that for non sex limited traits with moderate heritability (.35), incorporation of molecular information optimally applied in breeding programs, will only increase response by a few percentage points over several years and in the long term is actually detrimental (due to increase in rate of inbreeding and loss of polygenes from diverted attention on candidate genes). The optimal selection program is to weight each allele by it's contribution to the phenotype in a given environment. This weighting automatically occurs in standard breeding programs selecting on the phenotype (the whole is certainly easier and cheaper to measure than the sum of the parts). The few percentage points that can be gained in breeding programs using biotechnology may be crucial to large multi-national companies with unlimited budgets and where a few percentage points can make or break a company, but for developing countries is this where large amounts of resources should be invested? The economic resources could be better utilized bringing the management skills of the farmer up to the level of test stations. Perhaps investments in extension would be more profitable than biotechnology in those cases.

In contrast to the use of biotechnology in standard breeding programs, transgenic technology offers tremendous potential for developed and developing countries. Transgene technology offers the potential to increase food nutrient value, reduce chemical use and dependence, and improve disease resistance with sustainable impact. I strongly support this technology, however, possible adverse ecological impacts also need to be assessed and addressed to avoid potential negative impacts. The negative impacts also need to be evaluated relative to the true cost of the technology; which is the alternative. For example, BT impact needs to be compared to conventional insecticide usage and it's impact, but that is a discussion for another forum.

Bill Muir, PhD
Professor of Genetics
Department of Animal Sciences
Purdue University
W. Lafayette IN 47907-1151, USA
Phone 765-494-8032
FAX 765-494-9346
bmuir@purdue.edu http://www.ansc.purdue.edu/faculty/muir.htm

[In the last paragraph, it is slightly unclear if Professor Muir is referring only to transgenic crops. If his comments also refer to transgenic animals, it would be interesting if he (or anyone else) would like to provide more comments/views on the appropriateness of transgenic technology for the livestock sector in developing countries. This subject is currently quite topical following the article of McCreath et al in Nature 29 June ( http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v405/n6790/f ull/4051066a0_fs.html ), which describes a technique which could provide a general way of introducing specific genetic changes (gene-targeting), such as the inactivation of undesirable genes or the precise positioning of foreign genes, to other mammalian species (previously it was only possible in mice).

In addition, if anyone is interested in reading more about Bt and transgenic crops, I would refer to the Background Document and the archives of Conference 1 of this Forum ( http://www.fao.org/biotech/Conf1.htm ) held from March 20 - May 26 on the appropriateness of currently available biotechnologies in the crop sector for food production and agriculture in developing countries......Moderator]

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