Inheritance of Gray Leaf Spot Resistance in a Multiple Disease Resistant Maize Inbred.

Gray leaf spot is a fungal disease in maize caused by the pathogens Cercospora zeae-maydis and C. zeina (group I and group II). Number of dQTLs that confer resistance to gray leaf spot disease had been identified in all the ten chromosomes of Maize. In this study we used mixed models to characterize the inheritance pattern of gray leaf spot resistance in the northeast US in a multiple disease resistant inbred 22613, developed at Cornell University. Generation means analysis provides information on the relative importance of additive and dominance effects in populations generated from two inbreds. Our study used the means of nine generations (P1, P2, F1, F2, BC1P1, BC1P2 F3, BC1P1S1, and BC1P2S1) to improve prediction accuracy beyond that possible from the typical six-generation study. The multiple disease resistant inbred 22613 and susceptible inbred B73 were used for the crosses. We used the mixed-model approach of Peipho (2010) to account for the between–plot variance that is not accounted for in the Mather and Jinks (1971) model. Significant estimates of additive effects were observed for the gray leaf spot resistance in the generation means analyses. The dominant estimates were not significant. This confirms that the resistance to gray leaf spot in Corn is quantitative in nature for the inbred 22613. Also, the inbred 22613 has been identified to be resistant to Northern Leaf Blight, Southern Leaf Blight, Anthracnose Leaf Blight and Anthracnose Stalk Rot. The nature of this multiple disease resistance can be due to pyramiding of multiple resistance genes or a single pleiotropic region that confers resistance to multiple diseases or a quantitative trait locus that is made up of a number of disease resistance genes that are linked together. Understanding the inheritance pattern of gray leaf spot resistance will aid in the detection of mechanism behind multiple disease resistance in Corn.