HERITABILITY AND EARLY-GENERATION SELECTION FOR RESISTANCE TO EARLY AND LATE LEAFSPOT IN PEANUT

The genetic nature of resistance to early (Cercospora arachidicola Hori) and late [Cercosporidium personatum (Berk. & Curt.) Deighton] leafspot of peanut (Arachis hypogaea L.) is quantitative, making selection for resistance difficult in segregating populations. In many areas of peanut production, without fungicide application one or both diseases may significantly reduce yields. A study was conducted to obtain heritability estimates, responses to selection, and relationship of resistance of two peanut populations for early and late leafspot resistance. Selection based on F2 family means in the F3 generation via defoliation, infection, and sporulation was performed for early and late leafspot in North Carolina and Georgia, respectively, within populations of PI 314817/[TG3/EC 76446 (292)] and (PI 314817/ICGS 4). Divergent selections for each diseases were evaluated in the F4 generation at the same locations the following year for resistance by visual rating of infection and defoliation. Broad-sense heritability estimates ranged from low to high (0.12-0.88) for components of resistance to each leaf-spot disease. Narrow-sense heritability estimates from parent-offspring regression (0.18-0.74) and realized heritability (0.60-1.41) were significant for late leafspot resistance and early leafspot resistance in the PI 314817/[TG3/EC 76446 (292)] population. Results indicated that selection based on family means would be successful. Selection of individual plants within families did not significantly improve genetic progress. Moderate to high correlations (0.41-0.86) existed between early and late leafspot disease components indicating possible genetic linkage or host-plant physiology that conferred resistance to both diseases in one population.