Breeding for resistance to fall armyworm in sweet corn

The fall armyworm [Spodoptera frugiperda (J. E. Smith)] (FAW) is a serious pest of late-planted corn (Zea mays L.) in the southern USA. The objectives of this research were to evaluate the inheritance of resistance to FAW in sweet corn and to study the inheritance of selected morphological traits and their relationship with FAW damage. An inbred line of field corn resistant to FAW (Mp708) was crossed to seven inbred lines (R-4, R-10, R-16, R-20, R-24, R-33, and R-37) and four commercial single-cross hybrids (Honey ‘N’ Pearl, Illini Xtra-Sweet, Early Xtra-Sweet, and Illini Gold) of sweet corn containing the sh2 gene. Heritability estimates by variance components over two years were 0.40 for F₂ populations segregating for sh2, 0.47 for F₂ populations not segregating for sh2, and 0.61 for F₃ populations. Estimates of heritability in all F₂ populations were moderate to high when standard unit (r) and regression methods were used in combined analyses. The F₂ progenies gave a close fit to two genetic models: 12 susceptible:3 intermediate:1 resistant and 9 susceptible:6 intermediate:1 resistant. Several genetic models were considered for morphological traits. Correlation coefficients between morphological traits and FAW damage were generally low and non-significant.