Identification Of Quantitative Trait Locus For Yield Components And Combining Ability In Maize

The final objectives in maize breeding is developing grain yield. Maize inbred lines with high yield and combining ability is prerequisite for achieving a breakthrough in maize production. Therefore, the genetic dissection of yield components and combining ability is of great importance in maize breeding. In the study, a F2:3 families derived from NX531×YBP53 was used to QTL analysis of 11 yield-related traits based on SSRs under three environments. Furthermore, 120 maize inbred lines were crossed to two testers, zheng58, chang7-2, followed NCⅡmatting design and 240 testcrosses were obtained. Gnome-wide association analysis of yield-related traits and their general combining ability was applied to detect the molecular targets. In the last, comparison of the results in QTL mapping and association mapping were conducted. The major results are as follows:1. 203 F2:3 families were used to construct genetic linkage map based on 101 polymorphic SSRs. The genetic distance was 1179.8 c M, with an average of 11.68 c M.2. 144 QTLs were identified for 11 yield-related traits in F2:3 populations under 3 environments. All the QTLs unevenly distributed on 10 chromosomes. Contribution of single QTL to phenotypic variation varied from 0.03% to 25.65%. It was found that 42 QTLs were detected in different environments simultaneously, and 5 QTL-rich regions were detected in this study.3. Association analysis population consisting of 120 maize inbred lines was used to conduct genetic diversity analysis based on 195 SSRs. 1478 allelic variations were detected with an average of 7.58. The average of gene diversity and PIC value were 0.7016 and 0.6593, respectively. 120 maize inbred lines were clustered into 5 subpopulations, Reid, Lancaster, Tangsipingtou, Lvdahonggu and PB group, according to population structure analysis.4. Genome-wide association analysis of general combing ability for yield-related traits was carried out based on the genotype of inbred lines and phenotype of testcrosses. Under the-Log10P>2.5 level, 7 loci associated with GCA of yield were detected in 2 environment, located on chromosomes 2, 5, 6, 7 and 10. Phenotypic variation, explained by single loci, ranged from 4.67% to 22.14%. Furthermore, 5 GCA loci for plant height and 1 GCA loci for ear height were detected, distributed on chromosome 5, 9 and 2.5. Association analysis of yield-related traits was conducted based on phenotypic data of F1. 2 and 5 loci were detected strongly associated with plant height and ear height, respectively. A total of 12 associated loci were identified for yield in 2 environments, located on chromosomes 1, 2, 6, 7 and 9. Among those, 1 common loci mmc0241 was discovered in 2 environments, and explained 19.29% and 21.41% of phenotypic variation. Compared the results of linkage analysis and association analysis, it was found that yield-associated loci umc2393 and QTL for EW bnlg2122-umc2344 located the same chromosome region.