Abstract
Mechanism and inheritance of resistance to rice tungro disease in the rice varieties Basmati 370 and IR 50 were studied. Resistance of Basmati 370 was associated with its resistance to rice tungro spherical virus (RTSV) infection, which was controlled by a single recessive gene. Individual selection for its resistance to RTSV infection in the F2of a cross with a susceptible variety was effective in securing resistance in the F3. The RTSV resistance showed a genetic relation with heading date and grain width. Resistance of IR 50 was associated with its resistance to the green leafhopper (GLH), which was controlled by a single partially dominant gene. Individual selection for GLH resistance in the F2of a cross with a susceptible variety was ineffective in securing resistance in the F3. However, line selection in the F5was effective in securing resistance to GLH and virus infection in the later generations. Resistance to GLH in IR 50 was not related to heading date, culm length, panicle length, grain shape or resistance to the brown planthopper.
