Defoliation Effects on Two Corn Inbreds and their Single‐Cross Hybrid1

Abstract

AbstractHail damage to corn (Zea maysL.) is assessed with the use of loss charts derived primarily from research conducted with hybrids. Little data are available on the relative responses of inbreds vs. hybrids to defoliation. Therefore, field experiments were conducted at the University of Illinois on a Drummer silty clay loam (Typic Haplaquoll) in 1982 and a Flanagan silt loam (Aquic Argiudoll) in 1983 to compare the response to defoliation of two corn inbred lines, FRMol7rhmand FR27rhm, and their single‐cross hybrid. Defoliation treatments of 0,50, and 100% were conducted by hand at the 7‐leaf, 14‐leaf, anthesis, late‐milk, and soft‐dough stages in 1982 and the 7‐leaf, 14‐leaf, anthesis, milk, and dent stages in 1983. Data were taken on grain yield, kernel size, kernel number, and percentage barrens, doubles, and nubbins. The response of the inbreds was quite different than that of the hybrid and showed greater yearly variation because of differences in the growing seasons. Complete defoliation at anthesis reduced grain yield 100% in all cases. The greatest genetic variability was observed with 100% defoliation at the 14‐leaf stage, which reduced FRMol7rhmand FR27rhm✕ FRMo17rhmgrain yields by 90 and 40%, respectively, and increased FR27rhmgrain yields by 2%. In many cases, defoliation increased grain yields by decreasing transpiration or delaying flowering until irrigation water was applied. Yield reductions were due to decreases in kernel size and kernel number. Kernel size was affected most by defoliation at the milk and late‐milk stages. Kernel number was affected most by defoliation at anthesis and the 14‐leaf stage.