VARIETAL SCREENING AND INHERITANCE OF RESISTANCE TO BROWN SPOT DISEASE IN RICE (ORYZA-SATIVA)

A study was conducted to identify the new resistant varieties of diver se origin and inheritance of genes controlling brown spot disease. Ric e (Oryza sativa L.) varieties (560) from diverse sources were screened during wet seasons of 1990 and 1991 for brown spot (Cochilobolus miya beanus Ito & Kuribayashi) disease in the field under natural infection where high disease pressure was created by cultural operations. Twent y-two varieties were identified to be resistant to this disease. The i nheritance of resistance was studied during 1992-94 in 6 crosses invol ving 3 resistant parents and I susceptible parent. It was found that r esistance to brown spot disease was controlled by 2 pairs of recessive genes. The 3 resistant parents 'RR 35-4-1', 'RR 20-5' and 'RR 36-141' had single recessive gene in each. Gene present in 'RR 20-5' and 'RR 36-141' was the same whereas gene present in 'RR 35-4-1' was different from other 2 resistant parents.