ABSTRACT
INTRODUCTION Plant diseases cause billions of dollars in crop losses annually. Yield loss in rice alone is enormous. About 20% of total yield is lost because of biotic stresses, including severe diseases such as blast, sheath blight, bacterial blight, and tungro. Disease control is based on the principle of maintaining yield loss below an economic injury level. In most cases, agrochemicals such as fungicides /pesticides and biological control including, crop rotation, are used to control diseases. Developing varieties with disease resistance will most likely provide the best solution for disease control. This approach is inexpensive and environmentally friendly and management would be easier than before. The classic R gene, defined by plant breeders, is now isolated and characterized as a cloned gene and plant biotechnologists can transfer R genes along with pathogenesis-related genes into many crop plants, including rice (Van Loon, 1999; Datta and Muthukrishnan, 1999; Datta, 2002). R and PR genes are reported in Tables 5.1-5.3.
