Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/27/2005
Publication Date: 9/1/2005
Citation: Brooks, T.D., Willcox, M.C., Williams, W.P., Buckley, P.M. 2005. Quantitative trait loci conferring resistance to fall armyworm and southwestern corn borer leaf feeding damage. Crop Science. 45:2430-2434. Interpretive Summary: Leaf feeding by southwestern corn borer and fall armyworm cause reduced grain yield in southern U.S. corn production areas. Efforts to identify resistance in corn have led to the development of corn lines that exhibit less leaf feeding damage than conventional lines. In an effort to further understand the mechanism of resistance and aid in transferring it to elite corn inbreds, a study was initiated to identify the underlying genetic regions associated with resistance in Mp704, a resistant line, when crossed to Mo17, a susceptible line. Dual replicated field tests were artificially infested with fall armyworm or southwestern corn borer in each of three years and rated for foliar damage. Molecular techniques were used to find chromosomal regions associated with reduced leaf feeding damage. Eight chromosomal regions that influence resistance to southwestern corn borer and seven that influence resistance to fall armyworm were identified. Three of these regions, two with statistically significant effect, coincide for the two insect pests. Results also correspond to previously documented findings suggesting that these resistance regions are stable over environments. This study provides information on resistance in Mp704 and confirms that primary chromosomal regions influence both insect pests. Identifying these chromosomal regions associated with molecular markers will aid breeding efforts to transfer resistance to elite corn lines used in production of commercial corn hybrids. Growing resistant corn hybrids will reduce production costs and increase profitability of corn in the South.
Technical Abstract: Southwestern corn borer (Diatraea grandiosella Dyar) and fall armyworm [Spodoptera frugiperda (J. E. Smith)] damage ratings were measured on a F2-derived population segregating for leaf feeding resistance following artificial infestation with neonates. Damage ratings for each insect were recorded in replicated trials at three locations. Linkage maps were developed using simple sequence repeat markers. Quantitative trait loci (QTL) and their interactions were estimated using multiple interval mapping analysis. Resistance to southwestern corn borer leaf feeding was fit to a model containing eight QTL and two interactions explaining 20% of the phenotypic variation. A model containing seven QTL and one interaction best fit resistance to fall armyworm leaf feeding damage, and it explained approximately 14% of the phenotypic variation. Three QTL located on chromosomes 6, 9, and 10 affect leaf feeding damage ratings of both insects with similar effects and gene action. Minor interaction effects were observed. QTL on chromosomes 1, 5, and 9 correspond to previously identified resistant regions affecting resistance to southwestern corn borer. Insect resistance genes including the mir family of genes located on chromosome 6 and the glossy 15 locus on chromosome 9 fall within chromosomal regions of QTL predicted in this study. Multiple interval mapping reinforced previous documentation of the importance of QTL on chromosomes 1, 5, and 9 that reduce leaf feeding damage by southwestern corn borer in multiple environments. This study confirms that resistance to fall armyworm and southwestern corn borer involves many of the same QTL including, most significantly, the glossy 15 candidate locus on chromosome 9.