Inheritance and linkage relations of reaction to Xanthomonas phaseoli (E. F. Smith) Dowson (common blight), stage of plant development and plant habit in Phaseolus vulgaris L.

Summary

The inheritance of the reaction to Xanthomonas phaseoli (E. F. Smith) Dowson Nebraska isolate Xp-816, cause of common blight disease of beans Phaseolus vulgaris L. was studied in crosses between the late flowering, indeterminate, blight tolerant dry bean PI 207262 (Colombia) and susceptible cvs. GN 1140, an early flowering and indeterminate dry bean; Dark Red Kidney, a late flowering and determinate dry bean; and Gallatin 50, an early and determinate green bean. The tolerant disease reaction was dominant in the F₁. A continuous distribution of disease reaction ratings, skewed in the direction of dominance, occurred in the F₂ derived from the first 2 crosses while a slight bimodal distribution was observed in the F₂ of the last cross. A low narrow sense heritability estimate of 14% was calculated by the regression of F₃ progeny means on individual F₂ plants, in the cross GN 1140×PI 207262. The occurrence of a small number of nonsegregating families in a low number of F₃ families indicates that a small number of major genes were involved in controlling the disease reaction. Linkage did not appear to be involved between genes controlling early flowering (early maturity) and common blight tolerance. Coupling linkage occurred between genes controlling determinate plant habit and early flowering. A crossover value of 8.4% was estimated. Recombinants for early maturity, determinate habit, and blight tolerance were obtained. Transgressive segregation for early flowering and common blight susceptibility occurred in progeny derived from the cross of the two late-flowering blight tolerant lines, PI 207262 and GN Nebraska 1, sel. 27, indicating that the parents possessed different genes controlling these traits.