Developing varieties resistant to insect pest and diseases: An Eco-friendly Approach for Pest Management and Environment Protection

Large scale application of chemical pesticides to reduce the crop losses caused by insect pests and diseases, valued at over US$250 billion annually, has not only led to serious environmental hazards, but has also resulted in development of resistance to pesticides in pest populations. It is in this context that crop varieties capable of resisting pest damage will play a vital role in reducing crop losses and protecting the environment. Host plant resistance (HPR), is an economical and environment-friendly method of pest control. Development of crop varieties resistant to insect pests and diseases has been the major research thrust at ICRISAT for sustainable crop production. The most attractive feature of HPR is that it is the simplest seed-based technology for which farmers do not need any extra skill for application, and require no additional cash investment. Considerable progress has been made by multidisciplinary teams of scientists at ICRISAT in developing crop cultivars with resistance to the major pests of our five mandate crops (sorghum, pearl millet, groundnut, chickpea, and pigeonpea) that are largely grown under rainfed conditions. Using the conventional and molecular tools, resistance genes to major diseases and insect pests have been mapped, and some of these resistance genes have been, and are being transferred into agronomically elite and high-yielding varieties. Genes from the wild relatives of crops, and novel genes, such as those from Bacillus thuringiensis are also being introgressed into different crops to make “plant resistance” an effective weapon in pest management. Development and deployment of pest-resistant varieties will not only cause a major reduction in pesticide use and slowdown the rate of development of resistance to pesticides, but would also lead to increased activity of beneficial microorganisms, reduced pesticide residues in food and food products, and a much safer environment to live. Introduction Indiscriminate use of chemical pesticides has led to adverse effects on non-target organisms, pesticide residues in food and food products, resurgence of secondary pest problems, development of resistance in pest populations, toxic effects on human beings, and environmental pollution. Insect pests and plant pathogens (referred to as pests in the manuscript) have high reproductive rates, a fast generation turnover, wide genetic diversity, and an ability to withstand, metabolize, and avoid toxic chemicals. As a result, it has become quite difficult to control several pests through the currently available chemical pesticides. Therefore, it is important to adopt pest control strategies that are:  Ecologically sound,  Socially acceptable, and  Economically viable. Chemical pesticides (insecticides, herbicides, and fungicides) in general, are quite effective in controlling insect pests and plant pathogens. However, even if 90% of the pest population is killed with pesticides, the remaining population multiplies at a much faster rate in the absence of natural enemies (which quite often are eliminated by the pesticides) (Knipling 1979), and the farmers have to apply pesticides more frequently and at higher doses, which finally results in failure of control operations and increased environmental pollution. Heavy pesticide application has resulted in failure of pest control in several countries, and as a result, the farmers have to give up the cultivation of several crops.. Some cotton farmers have even resorted to committing suicide in India because of crop failures caused by cotton bollworm (Helicoverpa armigera) damage. Heavy insecticide use has led to an exponential growth in the number of insect species resistant to insecticides. Similarly, several plant pathogens causing downy mildews and late blights in various crops have developed resistance to fungicides used for their control. Therefore, it is important to place emphasis on