Heritability estimates of field resistance to spot blotch in four spring wheat crosses

Abstract

AbstractSpot blotch of wheat (Triticum aestivum L.), caused by Bipolaris sorokiniana (Sacc. in Sorok.) Shoem., is a major disease in South Asia. Popular commercial cultivars have low levels of resistance to spot blotch. Information on the inheritance of spot blotch resistance in wheat is lacking. Field studies were conducted in four wheat crosses, each involving a Chinese hexaploid parent with high levels of resistance and a commercial cultivar with low to intermediate levels of resistance to spot blotch. Data were recorded in the F2, F3 and F4 generations to estimate heritability. Field studies were conducted in three years (1992–94) at Rampur. Nepal, involving 150 lines in each cross. The spot blotch score was recorded as the percentage necrosis and associated chlorosis of the two upper most leaf surface. In the F2 generation three spot blotch readings on the flag leaf were taken whereas in the F3 and F4 generations four readings were recorded at 5‐day intervals on the flag and the penultimate leaves. The highest disease score (HDS) and the area under disease progress curve (AUDPC) were analysed. Heritability (h2) estimates for spot blotch resistance were intermediate to high measured in terms of HDS (0.47 < h2 < 0.67) and also AUDPC (0.58 < h2 < 0.77) both in F3 and F4 generations in each of the four crosses. Heritability values were somewhat higher for AUDPC than HDS. There were significant negative correlations (r) of days to heading with HDS (‐0.186 < r < ‐0.515) and AUDPC (‐0.218 < r < ‐0.623). One‐hundred kernel weight was significantly negatively correlated to AUDPC (‐0.245 < r < ‐0.454) in all crosses in each generation. The results suggest that selection for resistance to spot blotch could be effective in the segregating populations generated from hexaploid wheat parents having different levels of resistance. Although AUDPC appeared to be a better measure to determine genetic differences for spot blotch in wheat, HDS would be adequate in screening trials for resistance to spot blotch.