Harish Kumar

Bayer Seeds, Hyderabad, India.
 

Rice (Oryza sativa L.) is an important cereal crop in Asia. In order to address food security and strategy to enhance rice production under shrinking resources of arable land and soil quality and water availability, hybrid rice is being cultivated in many countries to increase rice yield to feed the ever-increasing human population. Hybrid rice gives an advantage of 15 to 20% increment of grain yield over inbred cultivars developed by various public sector organizations. Hybrid rice has certainly the potential to boost the stagnant yield of inbred rice varieties, thus, providing a clear-cut advantage of grain yield increment. However, hybrid rice has also increased the input cost of the farmers by purchasing pesticides to control various biotic stresses due to its extra attractiveness to various insect pests. Among the notorious pests of rice, the Brown planthopper (BPH), Nilaparvata lugens, Stal (Homoptera: Delphacidae) and the white backed planthopper (WBPH), Sogatella furcifera, Hovarth (Homoptera; Delphacidae) are the most dreaded insect pests of rice. Recently, pests have caused huge losses to farmers, particularly, after the adoption of hybrid rice. The pesticide application on hybrid rice to control these sucking pests has not yielded the desired results due to various reasons including the development of resistance against the most potent insecticide chemistries such as Imidacloprids. Among the other control measures, genetic resistance in rice has been advocated by various workers to be one of the alternative pest control tactics on rice because of its being carried in the rice seed, its effectiveness from seedling to harvest, environmentally safe, socially acceptable and economically feasible. The current paper describes the methods to development of some new sources of resistance using the methodology, which deviates, but complements the one developed and used by various public and private ventures. Experiments have been carried out to characterize resistance in the new sources of resistance by infestation by the standard methodologies as well as, by the ones developed and used in this paper. Several sources of resistance characterized by various workers to map resistance genes against BPH were found either susceptible or varied in their resistance at seedling stages and flowering stages. The new sources of resistance identified herein have been shown to display high level of resistance not only at different crop stages but also against 13 populations of BPH collected from various rice agro-ecosystems of India. The identified sources of resistance showed a good level of resistance against WBPH at seedling and flowering stages of the crop. The sources of resistance have been utilized very effectively to breed a rice hybrid AZ8433 DT with anti-xenosis type of resistance against BPH. The implications of using new sources of resistance in providing protection to the hybrids against BPH and WBPH under choice and no-choice situations have been discussed.

Key words: Nilaparvata lugens, Sogatella furcifera, planthoppers, rice breeding, BPH, WBPH, Oryza sativa, Homoptera. .