Rationale for Developing Herbicide-Resistant Crops

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Abstract
Herbicide-resistant crops (HRCs) have been used extensively during the past five decades, because crop tolerance is necessary for a selective herbicide. In the past, chemical company personnel screened a large number of organic compounds against a limited number of major crop and weed species to discover HRCs. Now a single herbicide can be evaluated for crop selectivity against a great number of biotypes of a single crop in tissue culture, or sometimes gene transfer can be used to produce tolerant genotypes. Thus, one can now choose an environmentally “benign” herbicide and search for or develop resistant crop cultivars. The advantages of these new HRCs are: (a) solutions may be more easily found for difficult weed management problems, (b) growers are more apt to use integrated weed management when they have effective backup weed control procedures if cultural or mechanical methods fail, (c) increased weed management options for growers of minor crops, (d) economic advantages to growers, and (e) increased use of more environmentally “benign” herbicides. Concerns about HRCs include: (a) these weed management procedures do not eliminate herbicides, (b) some believe biotechnology should not further herbicide use, (c) HRCs may become weeds, (d) this approach may facilitate less ecological diversity, (e) HRCs may increase herbicide use, (f) it could result in more herbicide carryover by facilitating the use of environmentally “harsh” herbicides, (g) HRCs may be less competitive to weeds, and (h) dependence on HRCs may decrease the weed control practices that a farmer uses. One needs to consider both the benefits and risks of HRCs to properly evaluate this technology.