Genetic Dissection And Application Of Disease Resistance To Gibberella Ear Rot And Gibberella Stalk Rot In Maize

Ear rot and stalk rot are the two most destructive diseases in maize.So far,many disease resistance QTL against stalk rot and ear rot have been identified,most of which have minor effect and are greatly affected by environment.Few studies on adoption of these QTL in resistance breeding have been reported.Therefore,it is necessary to mine new genetic loci with multiple disease resistant that could stably inherit across environments and generate resistant germplasm.In this study,176 F_6:7recombinant inbred lines（RILs）generated from91227 and Chang7-2 were used to map QTL for Gibberella ear rot resistance,Gibberella stalk rot resistance,plant height,ear height and day to pollen in maize under multiple environments.Furthermore,24 resistant lines were selected from a separate RIL population and crossed with two inbreds to generate 48 hybrid lines.The yield of the hybrid lines was measured under three environments.Ear rot resistance and fumonisin content were evaluated to select elite hybrid lines.The main results are as follows:1.The Maize6H-60K chip was used to determine the genotype of the RIL population（91227×Chang7-2）.The total length of the constructed genetic map was 4433.2 c M,with an average genetic distance between adjacent markers being 2.39 c M.Combining the GER phenotypic data from the four environments and BLUP,a total of 21 GER resistance QTLs were detected using the Win QTLcart 2.5 software composite interval mapping method.The QTL located in bin 3.07 explained the largest phenotypic variation,which was 14.60%,with a confidence interval of 13 c M.2.Two QTLs located in bin 7.03 and bin 7.04 was detected for GSR resistance,explaining12.39%and 10.74%phenotypic variation respectively,with confidence intervals between 9-10 c M.3.Two QTLs controlling plant height were detected in bins 1.03/04 and bins 1.04/05,explaining 15.11%and 9.31%of the phenotypic variation respectively.One QTL controlling ear height was detected in bin 4.06,explaining 10.53%of the phenotypic variation.Two stable QTLs controlling day to pollen was detected in bin 2.04 and bin 8.07,respectively.4.Co-localized disease resistance QTLs for GSR and GER were identified in bins 2.02,5.04 and 8.07.Bins 1.03/04 was associated with both plant height and ear height.5.Twenty-four resistant lines for Fusarium ear rot have been selected from a separate RIL populations previously.These lines were backcrossed with the two parents to generate hybrids.The yield and Fusarium ear rot resistance of the hybrids were measured under three environments.Six hybrids with good resistance and high yield were selected.Principal component analysis and cluster analysis showed that there was a clear group division among lines,which laid a foundation for breeding ear rot resistant inbred lines in Shaan A and Shaan B heterotic groups.