Quantitative trait loci conferring resistance to fall armyworm and southwestern corn borer leaf feeding damage

Southwestern corn borer (Diatraea grandiosella Dyar) and fall armyworm [Spodoptera frugiperda (J.E. Smith)] damage ratings were measured on an F2-derived maize (Zea mays L.) population segregating for leaf feeding resistance following artificial infestation with neonates. Damage ratings for each insect were recorded in replicated trials at three locations and used in conjunction with a genetic linkage map to identify quantitative trait loci (QTL) associated with resistance. Significant QTL and their interactions were estimated by 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. The QTL on chromosomes 1, 5, and 9 correspond to previously identified regions affecting resistance to southwestern corn borer. Insect resistance genes including the mir family of genes located on chromosome 6 and the glossy15 locus on chromosome 9 fall within chromosomal regions of QTL predicted in this study. This study confirms that resistance to fall armyworm and southwestern corn borer involves many of the same QTL and candidate genes for insect resistance include the glossy15 candidate locus on chromosome 9.