Selection for Spot Blotch Resistance in Four Spring Wheat Populations

Spot blotch of wheat ( Triticum aestivum L.), caused by Bipolaris sorokiniana (Sacc.) Shoem, is serious constraint in South Asia, and leading cultivars have low levels of resistance. The response to selection for low and high area under disease progress curve (AUDPC) of spot blotch in four wheat populations, involving different Chinese hexaploid parents with high level of resistance and a commercial cultivar moderately resistant to spot blotch, was investigated. Selections were made in the F 3 generation for low and high AUDPC of spot blotch and selected progenies evaluated in a replicated field test in the F 4 generation at Rampur, Nepal, in 1994. Selection in the F 3 for low and high AUDPC was effective in identifying F 4 lines with low and high AUDPC, respectively. Low AUDPC resulted in higher biomass and grain yield, higher harvest index, and 1000‐kernel weight. On average, the low AUDPC lines headed later than the high AUDPC lines. Realized heritability estimates for AUDPC were intermediate to high in magnitude (0.48 to 0.76). AUDPC was negatively correlated with biomass ( r = −0.195 to −0.451), grain yield ( r = −0.169 to −0.452), harvest index ( r = −0.256 to −0.597), days to heading ( r =−0.319 to −0.570), and 1000‐kernel weight ( r = −0.322 to −0.530). Results indicate that selection for low AUDPC of spot blotch in segregating generations would be effective in identifying wheat lines with high levels of resistance and would have positive effects on other characters.

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