Chapter 16
Agrochemistry: An Introduction
Downloaded by UNIV OF MASSACHUSETTS AMHERST on October 1, 2015 | http://pubs.acs.org Publication Date: January 7, 1988 | doi: 10.1021/bk-1988-0362.ch016
James N. Seiber Department of Environmental Toxicology, University of California—Davis, Davis, CA 95616
Biotechnology provides many new opportunities to advance the field of agricultural pest control by augmenting chemical-based technology as well as affording alternative approaches to pest control. Examples include the development of herbicide-tolerant crops, insecticidal seed coatings and insect-resistant crops, bioengineering approaches to producing pest control agents, immunoassays for their analysis, and bacteria and other microorganisms for decontaminating waste products. There i s a growing r e a l i z a t i o n that agriculture can benefit immensely from increased inputs of biotechnology, to complement and perhaps replace a dependence on chemical technology which has characterized much of the industry during the past several decades. To be sure, chemical technology has provided impressive gains i n f e r t i l i z a t i o n , growth regulation, pest control, animal health, and diagnostic techniques which have d i r e c t l y improved yields and q u a l i t y of many a g r i c u l t u r a l products. But these advances have been accompanied by undesirable side-effects — residue contamination, resistance, ecosystem impairments, and r e c a l c i t r a n t waste generat i o n . Some have even ascribed the economic problems of agriculture of recent years to an over-reliance on chemical technology — a s i m p l i s t i c view i n many respects, but one which nonetheless has stimulated a renewed interest i n "organic", "sustainable" and "lowinput" a g r i c u l t u r e . Whether p r o f i t a b i l i t y and environmental q u a l i t y can be improved i n modern farming by decreasing reliance on chemical technology w i l l depend i n large part on successful development of biotechnology-based a l t e r n a t i v e s . Certainly, many people believe that the p o t e n t i a l benefits j u s t i f y diversion of research and development c a p i t a l into the biotechnology f i e l d , a trend which i s already quite apparent i n the state a g r i c u l t u r a l experiment s t a t i o n s , USDA's A g r i c u l t u r a l Research Service, venture-capital firms, the food industry, and i n fact i n the agrochemical industry itself.
0097-6156/88/0362-0204$06.00/0 © 1988 American Chemical Society
In The Impact of Chemistry on Biotechnology; Phillips, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.
Downloaded by UNIV OF MASSACHUSETTS AMHERST on October 1, 2015 | http://pubs.acs.org Publication Date: January 7, 1988 | doi: 10.1021/bk-1988-0362.ch016
16.
SEIBER
Agrochemistry: An Introduction
205
Biotechnology i n the broad sense has long been practiced i n a g r i c u l t u r a l science i n general, and pest control i n p a r t i c u l a r . Breeding programs have produced disease- and insect-tolerant crops; natural product chemists and biochemists have i d e n t i f i e d a host of secondary chemicals which have proved useful as pest and disease control agents, and as growth regulators; microorganisms and t h e i r enzymes have been applied to waste decontamination; fermentation provides indispensable intermediates and end products of a variety of a g r i c u l t u r a l uses; and b i o l o g i c a l control agents (predators, bacteria, and viruses) have proven t h e i r worth as components of pest control arsenals. The new biotechnology w i l l build upon these leads, and carry them to new levels of efficacy and u t i l i t y as organisms are genetically modified to optimize the desired end-use
COMuch attention i s being devoted to development of herbicideresistant crop plants where c l a s s i c genetic s e l e c t i o n with whole plants i s a slow, tedious, and expensive path. Using c e l l culture s e l e c t i o n techniques, resistant mutants can be i d e n t i f i e d rather quickly, t h e i r chloroplasts combined with the nucleus of related species by c e l l fusion, and commercially viable resistant hybrids produced as the end r e s u l t . Crops tolerant of t r i a z i n e s , s u l f o n y l ureas, and glyphosate represent examples of t h i s technology. I t i s not far-fetched to envision that environmentally-friendly broad spectrum herbicides w i l l be emphasized i n the future, with s e l e c t i v i t y achieved by genetically engineering resistance into crops (2). Another example of the application of biotechnology to pest control l i e s i n the transfer of the gene regulating protein toxin production i n B a c i l l u s thuringiensis — a biocontrol agent i n widespread commercial use — to bacteria or plants. Toxin producing bacteria could be used i n seed coatings to protect germinating seedlings from attack by s o i l insects. Direct transfer of the B.T. gene to crop plants represents another promising avenue for crop protection, p a r t i c u l a r l y when the toxin can be confined to plant pests or l i f e stages which are i s o l a t e d from the harvested commodity of commercial value. There i s concerted interest i n pest control agents which work at low dosage l e v e l s , thus minimizing the quantity of material p o t e n t i a l l y available for residue contamination of the commodity and i t s environment. Some such agents represent complex natural products whose synthesis by conventional chemistry i s too d i f f i c u l t or expensive to be p r a c t i c a l . Biotechnology affords an approach wherein the organism which produces the active agent can be modified for use i n large-scale bioreactors, providing good y i e l d s , p u r i t y , and s t e r e o s p e c i f i c i t y i n the end product. An example l i e s i n the production of ivermectins by the actinomycete, Streptomyces avermitilis. Modification of the fermentation medium and of the organism, by mutation, resulted i n a 50-fold increase i n the y i e l d of avermectins from broth, opening the door to large-scale production of t h i s promising family of remarkably potent animal parasite control agents (3). Further genetic manipulation of t h i s and other organisms promises major advances i n the f i e l d of bioengineering applied to the production of hormones, pheromones, and pest control agents. In the area of analysis, operational benefits can be derived from the use of immunoassays to replace some c l a s s i c a l physico-
In The Impact of Chemistry on Biotechnology; Phillips, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.
Downloaded by UNIV OF MASSACHUSETTS AMHERST on October 1, 2015 | http://pubs.acs.org Publication Date: January 7, 1988 | doi: 10.1021/bk-1988-0362.ch016
206
THE IMPACT OF CHEMISTRY ON BIOTECHNOLOGY
chemical a n a l y t i c a l methods i n terms of speed, s p e c i f i c i t y , and lower costs. Immunoassays represent a here-and-now biotechnology with many examples of application to pesticide detection (4)· The use of hybridoma c e l l technology offers the p o t e n t i a l for providing a stable supply of antibodies f o r a given assay, of dependable e f f i c a c y . This technology can be used as the basis for f i e l d assay k i t s which might provide on-the-spot residue l e v e l s so that growers, pest control advisors, and regulators can assess residue levels i n terms of harvest i n t e r v a l s , reentry i n t e r v a l s , water holding times, and the l i k e . Adapted microorganisms can also be used to destroy waste pesticides r e s u l t i n g from s p i l l s , spray equipment rinsates, and disposal operations — applications o r g i n a l l y suggested by the p r o l i f i c biodégradation c a p a b i l i t y of microorganisms i n sewage sludge, eutrophic waters and sediments, and a g r i c u l t u r a l f i e l d s o i l s (_5). Once again, genetic engineering provides a p o t e n t i a l f o r t a i l o r i n g such organisms to better carry out what i s natural f o r them, perhaps at higher rates and i n unfamiliar environments. F u l f i l l i n g the promise of biotechnology i n these and other applications w i l l require careful planning to address health and safety issues, p a r t i c u l a r l y when g e n e t i c a l l y engineered organisms are to be released to the environment. Fortunately, these are f a m i l i a r concerns to pest control researchers, and many of the safety t e s t i n g protocols required now f o r chemical agents can be adapted to the products of biotechnology with appropriate changes i n monitoring t o o l s . Nevertheless, to convince a wary public that we know what we are doing, and that i t w i l l be b e n e f i c i a l to them, may require that we go to extra lengths i n safety evaluation — at least i n the early going. The p o t e n t i a l benefits to be gained j u s t i f y t h i s investment of time, energy, and c a p i t a l .
Literature Cited 1. Clarke, N.P. In 1986 Yearbook of Agriculture: Research For Tomorrow; Crowley, J.J., Ed; USDA, Washington, DC, 1986; pp 3741. 2. Schneiderman, H.A. "Overview of Innovation in Agriculture". Paper presented at the conference on Technology and Agricultural Policy, National Academy of Sciences, Washington, D.C., Dec 11-13, 1986. 3. Campbell, W.C.; Fisher, M.H.; Stapley, E.O.; Albers-Schönberg, G.; Jacob, T.A. Science 1983, 221, 823-828. 4. Hammock, B.D.; Mumma, R.O. In Recent Advances in Pesticide Analytical Methodology; Harvey, Jr., J . ; Zweig, G., Eds; American Chemical Society Symposium Series, Washington, DC, 1980; pp 321-352. 5. Alexander, M. Science 1981, 211, 132-138. RECEIVED August
6, 1987
In The Impact of Chemistry on Biotechnology; Phillips, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.
