Defoliation Effects on Two Corn Inbreds and their Single-Cross Hybrid1 (original) (raw)

Hail damage to corn (Zea mays L.) 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, FRMol7 rh and FR2Th, and their singlecross hybrid. Defoliation treatments of 0,50, and 100% were conducted by hand at the 7-leaf, ldleaf, anthesis, late-milk, and soft-dough stages in 1982 and the 7-leaf, ldleaf, anthesis, milk, and dent stages in 1983. Data were taken on grain yield, kernel sue, kernel number, and percentage barrens, doubles, and nubbins. The response of the inbreds was quite d8erent 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 ldleaf stage, which reduced FRMol7-and FR27h X F R M O~~'~ grain yields by 90 and 40%, respectively, and increased FR27'b grain 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 af€ected most by defoliation at the milk and late-milk stages. Kernel number was affected most by defoliation at anthesis and the 14-leaf stage. Additwnal index wonis: Zea mays L., Leaf removal, Yield components. AIL STORMS in the USA annually effect consid-' Contnbution.fr0.m the Dep. of Agronomy, ,Illionis Agric. Exp.