Abstract
Background：Kernel size are important agronomic traits for grain yield in maize. The objective of this study is to map QTLs for kernel size, fine map a stable QTL qKL-2 and predict candidate genes for kernel length in maize. A total 199 F2:3 lines were obtained from selfing F2 individuals from the cross SG5/SG7. In this study, a high density genetic linkage map with 3305 bin-markers spanning a total length of 2236.66 cM on 10 chromosomes was applied for primary QTL mapping. Composite interval mapping (CIM) method was used for detecting QTLs in three environments of F2 and F2:3 populations. Results：The result showed that a total ten QTLs for kernel size were detected, among which five QTLs for kernel length (KL) and five QTLs for kernel width (KW). Two stable QTLs qKW-1 and qKL-2 were mapped in all three environments. In order to validate and fine map qKL-2 , near isogenic lines (NILs) were developed by continuous backcross between SG5 as the donor parent and SG7 as the recurrent parent. Marker assisted selection was conducted from BC2F1 generation with molecular markers near qKL-2. Secondary linkage map with six markers around the objective region was developed for fine mapping qKL-2. Finally, qKL-2 was mapped in a 1.95Mb physical interval on maize chromosome 9 by blasting with Zea_Mays_B73 v4 genome. The results were confirmed with selected overlapping recombinant chromosomes. A total 11 out of 40 protein coding genes in the identified interval differentially expressed after conducting transcriptomic analysis between the two parents. GRMZM2G006080, which encodes receptor-like protein kinase FERONIA was predicted as candidate gene to control kernel size. Conclusions：A total ten QTLs for kernel size were identified. Two stable QTLs qKL-2 and qKW-2 were mapped in three envionments. Major QTL qKL-2 for KL was validated and fine mapped in a 1.95Mb physical interval. GRMZM2G006080 was predicted as candidate gene for qKL-2 to control kernel length. The work will not only help to understand the mechanisms that control kernel size of maize, but also provide new gene for marker-assisted selection in further studies.
Fine mapping and candidate gene prediction of the photoperiod and thermo-sensitive genic male sterile gene pms1(t) in rice