INHERITANCE AND ALLELIC RELATIONSHIP OF RESISTANCE GENES TO SPOT BLOTCH OF WHEAT CAUSED BY BIPOLARIS SOROKINIANA

摘要

Three varieties viz., Longmai 10, Jinmai and Sanghai, known for their resistance to spotblotch were crossed with a susceptible parent Sonalika. Disease severities of F_1 's wereintermediate to parents and thus indicated no dominance. Around 150-200 progenyrows of three resistant x susceptible crosses were evaluated in the F_3, F_4 and F5 generations. Spot blotch severity (%) for each progeny row was measured at three differentgrowth stages viz. 69, 77 and 83 (Zadoks scale, 1974). Based on disease score, F_3, F_4and F_5 progenies were grouped into three classes: homozygous resistant, homozygoussusceptible and segregating. Number of genes was estimated following x~2 and quantitative approach. Two parents showed two genes control while, Jinmai appeared to beunder the control of three genes. Resistant x resistant crosses were made to confirm the allelic relationship of resistance genes. The F_3 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-allelicrelationship. The study indicated the possibility of enhancement of resistance throughgene pyramiding.