Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2008
Publication Date: 8/1/2008
Citation: Ni, X., Krakowsky, M.D., Buntin, G., Rector, B.G., Guo, B., Snook, M.E. 2008. Identification of multiple ear-colonizing insect and disease resistance in CIMMYT maize inbred lines with varying levels of silk maysin. Journal of Economic Entomology. 101:1455-1465. Interpretive Summary: Ear-feeding insects have caused significant amount of economic losses in corn production by their direct feeding damage and elevated aflatoxin accumulation in corn grains. Because aflatoxin is one of the most potent known carcinogens in human, the mycotoxin contamination greatly reduces corn quality and marketability. However, only a few sources of corn germplasm are known to confer resistance to multiple ear-colonizing pests, including both insects and diseases. Following a previous experiment using 10 inbred lines and 10 experimental hybrids from Texas, we, in the present study, massively examined for ear-feeding insect resistance in 2005 and 2006 using 94 corn inbred lines obtained from the International Center for the Improvement of Maize and Wheat (CIMMYT) in Mexico. The agronomic traits of the CIMMYT inbred lines were also assessed at Tifton, Georgia. Ten inbred lines were identified as multiple insect-resistant lines with diserable agronomic traits. We conclude that development of multiple insect resistance is likely to be an important management strategy for yield and quality improvements in corn production.
Technical Abstract: Ninety four corn inbred lines selected from International Center for the Improvement of Maize and Wheat (CIMMYT) in Mexico were evaluated for levels of silk maysin in 2001 and 2002. Damage by major ear-feeding insects [i.e., the corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), the maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), the brown stink bug, Euschistus servus (Say), the southern green stink bugs, Nezara viridula (L.) (Heteroptera: Pentatomidae)], and common smut [Ustilago maydis DC (Corda)] infection on these inbred lines were evaluated in 2005 and 2006 under subtropical conditions at Tifton, Georgia. Ten inbred lines possessing good agronomic traits were also resistant to the corn earworm. The correlation between ear-feeding insect damage or smut infection and three phenotypic traits, silk maysin level, husk extension, and husk tightness of corn ears was also examined. Corn earworm and stink bug damage was negatively correlated to husk extension (P < 0.05), but not to either silk maysin levels (P = 0.74) or husk tightness (P = 0.14). In combination with the best agronomic trait ratings that show the least corn earworm and stink bug damage, lowest smut infection rate, and good insect-resistant phenotypic traits (i.e., high maysin and good husk coverage and husk tightness), 10 best inbred lines (CML90, CML92, CML94, CML99, CML104, CML108, CML114, CML128, CML137, CML373) were identified from the 94 lines examined. These selected inbred lines will be used for further examination of their resistance mechanisms and development of new corn germplasm that confers multiple ear-colonizing pest resistance.