Biotechnologies of Obtaining Herbicide Tolerance in Potato

Abstract

The control of weeds is a worldwide problem. Infestations of weeds increase insect and disease problems and compete with the potatoes for nutrients, moisture and light resulting in reduced yields of between 16% and 76% (Neild and Procter 1962; Chitsaz and Nelson 1983). Weeds are generally controlled by soil-applied herbicides supplemented with machine or hand cultivation. Although herbicides reduce the number of cultivations, they are expensive. Costs of weeding range from $ 10 ha^-1 for cultivation up to $ 93 ha^-1 for herbicides (Chitsaz and Nelson 1983). In Eastern Europa and most of the Third World, areas that produce the largest percentage of the world crop (Van der Zaag and Horton 1983), limited herbicide availability magnifies the problem. Even in Europa and North America where herbicides are readily available, supplemental cultivation is required. The available herbicides tend to have a short, soil residual life and potato cultivars are susceptible to these under certain environmental conditions (Freeman 1982). Chloracetamide and as-triazine, the most effective potato herbicides available, can cause stunting and reduced yields on certain varieties (Weller et al. 1979, Freeman 1982). These problems necessitate numerous cultivations. Cultivations done prior to hilling have the sole purpose of eliminating weeds. Once the potatoes are hilled, existing weeds within the row are difficult to control as cultivation is impractical and no post-emergent herbicides are safe or available for use. Even though Aldrich et al. (1954) have shown that more than two or three cultivations per season can reduce yields, presently, in most regions of the world due to limited herbicide availability and costs, numerous cultivations for weed control are the standard practice.