Improvement of resistance to Fusarium head blight by recurrent selection in an intermating breeding spring wheat population using the dominant male-sterile gene ms(2)

Four cycles of recurrent selection for FHB resistance were conducted in an intermating wheat breeding population using the dominant male-sterile gene ms(2) during 1987-1991. Five cycles of phenotypic mass selection for male-s terile plants were evaluated using the soil-surface inoculation method in E xperiment I. Experiment II evaluated changes in FHB scores during five cycl es of progeny selection for fertile plants using the single-floret inoculat ion method. In Experiment I, the average level of FHB response increased to MR level in C-4, compared to MS level in C-0. The numbers of infected spik elets and diseased kernels decreased 0.32 and 2.68 per cycle, respectively. In Experiment II, the average level of FHB response increased to R level i n C4F1. The numbers of infected spikelets and diseased kernels decreased 0. 93 and 4.58 per cycle, respectively. In both experiments, the largest selec tion gains were realized in the first cycle. The frequencies of R and MR in dividuals were increased significantly. The frequencies of individuals with FHB response equal and/or superior to Sumai 3 were increased to 5-8% in C- 4 and 25% in C4F1 after the fourth cycle. Agronomic traits tended to be sli ghtly improved in selected populations. Compared to 2% in C-0, about 34% of lines superior in both FHB resistance and agronomic traits in C4F1 were se lected to enter the conventional breeding program for further evaluation. S ixty three semidwarf lines superior in both FHB resistance and yield potent ial were selected from the F-5 generations derived from C1F1 to C4F1. From them, two resistant cultivars with high-yielding potential were developed a nd commercialized in the Lower Yangtze Valley. Recurrent selection appears to be highly effective and feasible in shifting the average FHB response of the intermating population in the desirable direction, thereby enhancing t he frequency of resistant individuals.