New Insight in Herbicides Science: Non-Target Site Resistance and Its Mechanisms

Managing weeds in crop production, whether in the field, or greenhouse, can be troublesome; however, it is essential to successful production. Weeds compete with the crop for nutrients, space, sunlight and also host plant pathogens and insect pests. The economic impacts of weeds include both monetary and non-monetary. In Australia, the overall cost of weeds to grain growers is estimated at AUD 3.3 billion annually. In India, weeds cost over USD 11 billion each year. In the USA, weeds cost USD 33 billion in lost crop production annually. Herbicide use is indispensable in agriculture as it offers tool for weed management; however, repeated applications of herbicides with the same mode of action resulted in the selection of herbicide-resistant weed populations. Herbicide resistance is a rapidly growing worldwide problem that causes significant crop yield losses as well as increases in production costs. Non-target-site resistance to herbicides in weeds can be conferred as a result of the alteration of one or more physiological processes such as reduced herbicide translocation, increased herbicide metabolism, decreased rate of herbicide activation. Non-Target Site Resistance mechanisms are generally more complex and can impart cross-resistance to herbicides with different modes of action. To date, approximately 252 species have evolved resistance to 23 of the 26 known herbicide modes of action.