| Maize is one of the most important cereal crops. The decrease of arable land and increase of population make the global supply and demand situation more and more tense. In addition, as an upland crop, maize production is frequently affected by drought, and drought becomes one of the most important abiotic stresses. Study on the genetic basis of grain yield-related traits and drought resistance will contribute to achieving the goal of high and stable yield. In this study, two sets of maize introgression lines derived from the crosses of HuangzaosixCML343and Zong3×Hengbai522respectively were used to investigate yield and yield related traits, drought resistance traits at seedling stage at middle parent heterosis under multiple environments. Significant loci associated with these traits were also identified with SSR markers. The main results are listed as follow:1. For the137introgression lines from the cross of Huangzaosi×CML343,201SSR markers were analyzed. Introgressed segment in each line ranged from14to38with an average of22.5in this population. Background recovery rate ranged from63.0%to86.1%with an average of76.0%. A total of98significant loci associated with12yield and yield related traits under3environments with software Graphical Genotypes (GGT)2.0. Except for grain yield per plant (YP) and ear number per plant (EN),2to21significant loci were detected under at least two environments for the other10traits. Six important QTL clusters were mapped on chromosome1,2,5,7,9and10, and each locus was associated with more than one traits under at least two environments.2. Degree of leaf-drying under medium drought stress (LDM), degree of leaf-drying under severe drought stress (LDS) and three root traits under severe drought stress condition in the Huangzaosi introgression lines were investigated under two environments. Results showed that LDM was significantly correlated to LDS, however, they were negatively correlated to the three root traits:root length under stress (RLS), root number under stress (RNS), and root weight under stress (RWS). A total of97significant loci were detected for the5traits under two environments. Among them,31and25significant loci for LDM and LDS were identified, respectively, and17of them were commonly detected under both environments. For the three root traits,41significant loci were detected with20loci identified under both environments. Of these significant loci,20controlled LDM and LDS simultaneously and19loci related to both leaf-drying degree and root traits under stress.3. Heterotic loci (HL) for seven yield and yield-related traits under two environments were identified with another set of introgression lines derived from the cross of Zong3xHengbai522and the F1population individually derived from introgression lines crossing with one of their parents, Zong3. Middle parent heterosis (MPH) of the seven yield and yield-related traits was calculated based on the field experiments conducted at two locations. The results showed that the MPH of grain yield per plant (YP) was significantly correlated with the MPH of other six yield-related traits. A total of120significant loci for the traits were identified by calculating marker-trait coefficients with software GGT2.0, and48loci represent for five traits were commonly identified under two environments.36,10,25,14and33HL were detected for YP,100-kernel-weight (KW), ear length (EL), kernel number per row (KN), plant height (PH), but only two HL were identified for ear diameter (ED). For yield and most of the yield-related traits, the heterozygosity rates of the markers at the HL were strongly correlated to the performance of middle parent heterosis.Results in this study could provide useful maeker information to develop maize inbreds or hybrids with high yield and drought resistance. Meanwhile, according to the QTL mapping result for yield traits and drought resistance indicators, we can develop Near Isogenic Line (NIL) at the target QTL region, which will lay a foundation for the fine mapping and clone of these genes. |
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