Selection Effectiveness for the Resistance to Net Blotch in Barley

Selection effectiveness for the resistance to net blotch was estimated by using two sets of F2 and F3 populations derived from the crosses between resistant and susceptible parents. In every F2 and F3 population, disease ratings showed a continuous distribution. As many F3 lines with intermediate resistance had a smaller variance and homozygous genotype, the resistance might be controlled by a few genes. The heritabilities of the disease rating were estimated　by correlation coefficients and regression coefficients between each F2 plant and the descended F3 lines. Another estimate for heritability was calculated by the selection differential in the F2 plants and genetic gain in the F3 lines. Despite the different level of resistance in the resistant parents of the two crosses, the three kinds of heritabilities estimated were similar and ranged from 0.6 to 0.8. Because of the fewer number of genes controlling the disease resistance and the higher heritabilities, selection in a early generation may be effective for net blotch resistance in barlcy.