Inheritance of resistance to spot blotch caused by Bipolaris sorokiniana in spring wheat

Abstract Three F 1 progenies and their families in the segregating generations (F 3 , F 4 , F 5 and F 6 ), obtained after crossing resistant × susceptible wheat genotypes were studied in the field to determine the genetics of resistance to spot blotch caused by Bipolaris sorokiniana. Spot blotch scores in the F 1 generation showed absence of dominance. Individually threshed F 2 plants were used to advance the generations. Progenies (200‐250) of resistant genotypes Acc. No. 8226, Mon/Ald, Suzhoe#8 crossed with susceptible ‘Sonalika’ were evaluated in the F 3 , F 4 , F 5 and F 6 generations under induced epiphytotic conditions. Based on disease score distribution in individual progeny rows, F 3 progenies were grouped into four classes: homozygous resistant, homozygous susceptible, segregating resistant and segregating susceptible. Resistance appeared to be under the control of three additive genes. The presence of three genes was also noted in the distribution of F 4 and F 5 lines. In the case of F 6 progeny rows, both quantitative and qualitative models were used to estimate the number of segregating genes based on a 2‐year trial. It appeared that resistance to spot blotch was controlled by the additive interaction of more than two genes, possibly only three.