Developing scald resistant barley germplasm utilizing traditional and marker screening techniques

Abstract

Scald, caused by Rhynchosporium secalis (Oud) J. J. Davis, is present in most barley growing areas. Annual losses caused by the pathogen average 1 - 10%, but losses of 30 - 40% can occur. It is difficult to breed for disease resistance because of high pathogen genetic variability. In this study, progenies of four crosses of resistant (SM89010, CDC Silky) and susceptible (Harrington) barley cultivars were evaluated for scald in the F2 to F4 generations with traditional screening methods and marker assisted selection, using Random Amplified Polymorphic DNA. Plants were evaluated using a 0 to 3 scale, with score 0 for a resistant and 3 for a susceptible reaction. Two Canadian isolates of R. secalis, 1493 and 1824, were used in the study. Crosses and screening of the plants at all generations were performed in a greenhouse environment. Distribution of the progeny disease reaction was skewed toward resistance. Progeny reactions were tested using Chi-square analysis to determine the fit to hypothesized ratios. Crosses 1 and 2 fit the hypothesized ratios for the single dominant gene model in F2 and F3 generations. Cross 3 was designed to develop a marker for a resistance gene, which was not successfully mapped. The segregation ratio for cross 3 at the F2 population did not fit the hypothesized model for single dominant gene or two dominant genes. Progenies from Cross 4 fit the two gene hypothesized model in the F2 generation. Resistance to R. secalis was inherited qualitatively.