QTL Mapping For Maize Ear And Kernel Traits Under Different Environments And Confirmation Of A Major QTLs For Maize Kernel Row Number

The maize production is affected by various biotic and abiotic stress, and is closely related with the ear and kernel traits. To identify the key QTL/gene for maize yield that could be used in the maize breeding by QTL mapping or GWAS is of great importance for maize yield improvement. In this study, in order to dissect the QTL controlling maize ear and kernel traits, we constructed an integration and consensus map for maize yield related traits. With the derivative F2:3and F2:4families to do QTL mapping for maize ear and kernel traits, and get the major QTL for maize kernel row number. Based on the primary mapping results, we foused on a major QTL on chromosome10for kernel row number and three segregation populations were constructed to confirm it. At the same time, we used genome-wide association mapping strategy to decipher the genetic basis of maize kernel row number in order to find more closely related SNPs. The main results are as follows:1. In this research,946QTL for grain yield and its related traits in maize were collected from36experiments and were used to construct the integration and consensus map. QTL-Finder was used for QTL integration and meta-analysis with IBM22008Neighbors as a reference map. As shown in the result, the QTL for maize yield and related traits were unevenly distributed on all10chromosomes, with most of174QTL on chromosome1and least of62QTL on chromosome10. QTL for ear length,100kernel weight, kernel number per row and grain yield were mainly distributed on chromosome1, while QTL for cob diameter and kernel width on chromosome1and2, QTL for ear diameter are mainly on chromosome1and5. QTL for other traits are evenly distributed on the10chromosomes. Two-hundreds and eighty-seven consensus QTL for grain yield and its related traits were identified by the meta-analysis function of QTLFinder, some consensus QTL for different traits located on the same or near chromosome regions. These results provide a good basis for studying genetic mechanism and molecular marker assisted selection for maize yield improvement.2. In this research, six ear and kernel related traits including ear weight, ear length, ear diameter, kernel number per row, cob weight and kernel weight, were investigated using F2:3and F2:4populations, which were derived from two inbred lines of Y1648and Y2348cultivated by our lab. Respectively, the two populations were evaluated under different regions in2008and2009. The results showed that the maize ear and kernel traits under the same environment are significantly correlated, except for ear diameter and ear length, the same traits under different environments are significantly correlated. A total of33QTLs for maize ear and kernel traits were identified under different environments, including12QTLs for maize ear diameter,7QTLs for ear weight,4QTLs for ear length,4,1,6for cob weight, kernel number per row and kernel weight respectively. The phenotypic variation explained by each QTL is from6.22-14.96%, some QTLs can be detected under more than one environments. These results may help to further elucidate the genetic basis of maize yield.3. In this paper, with the F2:3and F2:4population development from two inbred lines of Y1648and Y2348cultivated by our lab,13QTLs for maize kernel row number are identified under different environments, and these QTL are distributed on chromosome2、3、5、8and10, for each single QTL can explain5.52%to12.95%of the kernel row number variation. Meantime, with a BC3F2:3population developed from the same two parental lines,4QTLs located on chromosome5and chromosome10for maize kernel row number are identified under two environments, the contribution for each single QTL is between9.19%and34.59%, the QTL on chromosome10between ssr1430and umc1077is in good accordance with the QTL identified in the F2:3and F2:4population, and can explain more phenotype variation. Three BC5F2:3populations which segregated at qKRN10, the major QTL for maize kernel row number on chromosome10were used to reconfirm the target QTL. The lines that could amplify the same size with Y2348at the marker loci umc2348and umc1077generally have more maize kernel row number than lines that amplify the same product with Y1648, while the heterozygous lines are between the two homozygous types, the maize kernel row number between different genotypes are significantly varied. Though we could not mendelize of this QTL, we confirmed this locus in the marker region from ssr1430to umc1077. This result further confirm the major QTL for maize kernel row number on chromosome10and imply the possibility for fine mapping and map-base cloning of this major QTL.4. By the MLM model of TASSEL3.0,390SNP significant loci that associate with the kernel row number were identified. And35SNP could be detected under2environments,4SNP under3different environments,2SNP for kernel row number under4conditions, these SNP supply a good basis for the gene discovery for maize kernel row number.