QTL Mapping Of Starch Content In Maize Kernel

Currently, maize is not only one of the most important food crops in world, but also the largest food crops in China. Starch, one of the main maize kernel compositions, accounts for 60% to 70% of kernel compositions. Thus, starch has a great influence on the yield and quality of maize. In addition, maize starch is one of the most important raw material in starch industry. Therefore, increasing starch content in maize kernel is one of the key targets in maize breeding. In this study, two RIL populations were developed by a comment founder K22 intercrossed with high oil founder BY815 and normal founder CI7, respectively. QTL for kernel starch content were detected by linkage analysis in single population and joint-linkage analysis using the BLUP value of starch content in three environments. The main results are as follow:1. The starch content of maize kernel has a wide range of variation in the two RIL populations. In population BY815/K22, the mean of starch content is 60.84% with a range from 54.1% to 66.53%. In K22/CI7 RIL population, the mean of BLUP is 64.82% with a range from 61.36% to 69.52%. ANOVA analysis indicated the significant effects on starch content are due to genotype as well as environment. The broad-sense heritability estimates of starch content were 81.2% in BY815/K22 RIL population and 82.1% in K22/CI7 RIL population, respectively.2. QTL for starch content were identified using the BLUP values of starch content in three environments and high-density genetic linkage maps in two separate RIL populations. In BY815/K22 RIL population, 8 QTL for starch content, collectively explaining 59.9% of the total phenotypic variation were detected with the explained phenotypic variation of each single QTL ranging from 3.38% to 13.12%. And the favorable alleles of the 8 QTL come from K22. In K22/CI7 RIL population, 6 QTL were detected for starch content. Each QTL accounted for 4.69% to 10.62% of phenotypic variation, and all QTL collectively explained 48.6% of the total phenotypic variation. Except one QTL’s favorable allele come from CI7, the others’ favorable allele come from K22. What’s more, a common QTL was detected in the two RIL populations.3. A total of 16 QTL were detected for starch content by joint linkage analysis. Each QTL explained 2.3% to 12.4% of phenotypic variation. The additive effects of QTL mapping tothe same locations were different(and sometimes opposite) in different RIL populations. Compared with QTL identified in two separate populations, 13 QTL were common and 4 QTL were only detected in joint-linkage analysis, which showed joint-linkage analysis had higher power in identifying QTL.