Further studies on the incidence and genetics of rust resistance in sorghum

The incidence of rust is higher under humid condition of Dharwad consequently increasing the susceptibility of the hypersensitive parents and frequency of susceptibles in F sub(2). There is no evidence for the existence of more than three genes even at Dharwad leading to the conclusion that the differential behavior is due to the increased inoculum attributable to favourable environment rather than the occurrence of different physiological races of the fungus. Rust resistance is confirmed to be trigenic recessive of the r sub(1)r sub(1)r sub(2)r sub(2)r sub(3)r sub(3) genetic constitution. Modifying factors appear to push a hypersensitive reaction towards susceptibility under more favourable conditions for disease development.