ABSTRACT
The occurrence of plant diseases and their counterattack for self-defense might have evolved simultaneously. Every plant species possesses its own immune system, which signals a cellular response and leads to the death of the attacking pathogen. Plants recognize pathogen-encoded molecules through probable receptors encoded by disease resistance (R) genes. A signal transduction study provides an excellent understanding of gene-for-gene resistance, which explains plant pathogen co-evolution in a given environment [1]. Plant diseases cause billions of dollars in crop losses annually. Yield loss in rice alone is enormous. About 20% of total yield is lost due to biotic stresses, including severe diseases such as blast, sheath blight, bacterial blight, tungro, etc. Disease control implies that it 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 [2-4]. R and PR genes are listed in Tables 1-3. A few selected areas such as transgenic research with R and PR genes and expression of those genes in transgenic crop plants leading to strategic management of diseases are stressed here.
