Inheritance And Allelic Relationship Of Resistance Genes To Spot Blotch Of Wheat Caused By Bipolaris Sorokiniana

Three varieties viz., Longmai 10, Jinmai and Sanghai, known for their resistance to spot blotch were crossed with a susceptible parent Sonalika. Disease severities of F1’s were intermediate to parents and thus indicated no dominance. Around 150–200 progeny rows of three resistant × susceptible crosses were evaluated in the F3, F4 and F5 generations. Spot blotch severity (%) for each progeny row was measured at three different growth stages viz. 69, 77 and 83 (Zadoks scale, 1974). Based on disease score, F3, F4 and F5 progenies were grouped into three classes: homozygous resistant, homozygous susceptible and segregating. Number of genes was estimated following χ2 and quantitative approach. Two parents showed two genes control while, Jinmai appeared to be under the control of three genes Resistant x resistant crosses were made to confirm the allelic relationship of resistance genes. The F3 progenies of all the crosses did not show susceptible plants. This proved that at least one gene was common among parents for resistance. However, the appearance of transgressive segregants was an indication of the non-allelic relationship. The study indicated the possibility of enhancement of resistance through gene pyramiding.