Heritability Of Resistance To Bacterial Streak In Winter Wheat

Bacterial streak caused by Xanthomonas campestris pv. translucens reduces yield of wheat [Triticum aestivum (L.) em Thell] worldwide. Attempts to control the disease with bactericides have been unsuccessful. Resistant cultivars offer the best protection against yield loss, but little is known about the inheritance of resistance. The objectives of this study were to estimate the heritability of resistance to bacterial streak in soft red winter wheat and to derive an effective strategy for selecting resistant genotypes. About 60 F-2:3 and F-2:4 lines from each of three populations (Pop1, Pop2, and Pop3) were tested for resistance to bacterial streak in three Louisiana environments with two to three replications per environment from 1991 to 1994. Variation due to genotype x environment (GxE) interaction occurred in each of the populations and was one-fourth to one-half the magnitude of error variance. Heritability of resistance to bacterial streak was relatively low and ranged from 0.12 to 0.70 (average 0.31) with parent-offspring regression and from 0.18 to 0.40 with variance components (average 0.36). Heritability increased by 0.22, 0.29, and 0.29 for Pop1, Pop2, and Pop3, respectively, with means of two replications and two environments. Non-normal distributions in two of the three populations may have inflated estimates of heritability. Across populations, four lines were resistant in all three environments and 12 lines were resistant in two of three environments. Because of GxE interaction, testing should be conducted with at least two replications in two environments under high disease pressure. Such a testing program should be effective in selecting wheat lines resistant to bacterial streak.