Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2007
Publication Date: 10/1/2007
Citation: Ni, X., Xu, W., Krakowsky, M.D., Buntin, G.D., Brown, S.L., Lee, R.D., Coy, A.E. 2007. Field Screening of Experimental Corn Hybrids and Inbred Lines for Multiple Ear-Feeding Insect Resistance. Journal of Economic Entomology. 100(5):1704-1713. Interpretive Summary: Ear-feeding insects have caused significant amount of economic losses in corn production. Insect damage on corn ears also provides the entrance for fungal infections that are called ear rot and consequently aflatoxin accumulation in corn grains. Because aflatoxin causes cancer in human, such contamination reduces corn quality and marketability. However, no corn germplasm is known to confer multiple ear-feeding insect resistance. The possibility of developing multiple ear-feeding insect-resistant maize inbred lines with good agronomic traits for the southeastern coastal plain region has been examined by the corn breeding program in the USDA-ARS Crop Genetics and Breeding Research Unit at Tifton, GA location. After examining of 10 experimental hybrids and 10 inbred lines, we identified two corn inbred lines two experimental hybrids that confer multiple ear-feeding insect resistance. We conclude that development of multiple insect resistance is likely to be one of the important management strategies for yield and quality improvements in corn production. Such improvements are critical to meet the ever-growing demand of corn as a key animal feed component for food security, as well as a key carbon source for bio-energy (ethanol) production in energy security.
Technical Abstract: Identifying and utilizing native insect resistance genes is the core of integrated pest management. In this study, ten experimental corn hybrids and ten inbred lines were screened for resistance to major ear-feeding insects in the southeastern Coastal Plain region of the U.S.A. during 2004 and 2005. Ear-feeding insect damage was assessed at harvest by visual damage rating for the corn earworm, Helicoverpa zea (Boddie), and by the percentage of kernels damaged by the maize weevil, Sitophilus zeamais Motschulsky, and stink bugs [combination of Euschistus servus (Say) and southern green stink bug, Nezara viridula (L.)]. Among the eight inbred lines and two control populations examined, C3S1B73-5b was resistant to corn earworm, maize weevil, and stink bugs. In contrast, C3S1B73-4 was resistant to corn earworm and stink bugs, but not to maize weevil. In a similar manner, the corn hybrid S1W*CML343 was resistant to all three ear-feeding insects, while hybrid C3S1B73-3*Tx205 was resistant to corn earworm and maize weevil, but susceptible to stink bug feeding in both growing seasons. The silk-feeding bioassay showed that corn earworm developed better on corn silk than did fall armyworm. Among all phenotypic traits examined (i.e., corn ear size, husk extension, and husk tightness), only corn ear size was negatively correlated to corn earworm damage in the inbred lines examined, while only husk extension (i.e., coverage) was negatively correlated to both corn earworm and maize weevil damage on the experimental hybrids examined. Such information could be used to establish a baseline for developing agronomically-elite corn germplasm that confers multiple ear-feeding insect resistance.