MATERNAL INFLUENCE ON THE RESISTANCE OF SWEET CORN LINES TO KERNEL INFECTION BY FUSARIUM-MONILIFORME

Sweet corn inbred lines resistant and susceptible to kernel infection by Fusarium moniliforme were hand pollinated to produce parental, F1, F2, F3, and backcross generations with reciprocals to examine maternal effects on resistance. Silks of half of the hand-pollinated plants in each generation were inoculated with F. moniliforme. Incidence of symptomatic and asymptomatic infection of kernels by F. moniliforme was determined from inoculated and uniculated ears. Factors operative in maternal tissues had a strong influence on the response of sweet corn lines to kernel infection by F. moniliforme and were not influenced by the cytoplasm, endosperm, or embryo. Infection of kernels produced on resistant parents (P(R), F1, and backcross generations) was less than that of kernels produced on susceptible parents (P(S), F1, and backcross generations). Infection of kernels produced on the same ear parent was not significantly different regardless of generation. Maternal tissues that may influence the resistance to kernel infection include the silk, pericarp, and closing layer. Silks that grew actively for several days after pollination inhibited kernel infection by F. moniliforme and therefore appeared to be the maternal tissue most likely to influence kernel infection. The implications of these findings in breeding for resistance to kernel infection by F. moniliforme are to select inbred parents for delayed senescence of silks and to use identified sources of resistance, such as IL125b, as the ear parent in seed production.