Fine Mapping And Candidate Gene Analysis Of Qhkw5-3,a Major QTL For Hundred-kernel Weight In Maize

Kernel weight,which is one of the maize yield key factors,the genetic mechanism of kernel weight is studied,it is the great value for high yield molecular design breeding of maize.In our group previous study,based on the genetic background of maize inbred line Zheng58,there was the substitution line homozygote Z22 as material,which only one derived from the chromosome fragment of Chang7-2,based on(Zheng58×Z22)×Z22 constructed BC1F2 segregation population mapped the hundred-kernel weight gene qhkw5-3 between the SSR molecular markers SYM077 and SYM084,the physical interval is 442.6kb.This study is based on these previous studies,the selected homozygous materials and the Iin Del molecular markers developed in the target region were used to fine mapping the qhkw5-3,and the candidate genes in the target region were analyzed.The main studies are as follows:1.Based on the resequencing results of Zheng58 and Chang 7-2,48 pairs of indel molecular markers were designed between ssr molecular markers SYM077 and SYM084,of which 11 pairs of indel markers were polymorphism between parents.11 pairs of indel markers were used to detect 6 pureboids between ssr molecular markers STM077 and SYM084 and flanking in BC1F4 generation.Based on the molecular marker genotyping and kernel hundred weight phenotypic analysis of 6 homozygotes,qhkw5-3 was located between the molecular markers In YM20 and In YM6.At the same time,the grain length,grain width,grain thickness and grain density of the six materials were not detected.The corresponding QTL was not detected.2.Seven homozygotes in the BC1F5 generation were selected to increase the planting population in the field and repeat three times.The hundred kernel weight was examined after fruit ripening,and the genotype of 7 homozygotes was combined with the genotype of 7 homozygotes.By means of overlapping group analysis,the qhkw5-3 was again located between the molecular markers In YM20 and In YM36.The physical distance between the two markers was 125.3 kb,and the heritability of hundred kernel weight was 0.9580.Using the same method,the grain length,grain width,grain thickness and grain density of the 7 sample were analyzed.The results showed that the corresponding QTL was not detected.3.According to the existence of 6 protein coding genes in In YM20 and In YM36 region of B73 Refgen-V4,the sequence alignment bioinformatics and q RT-PCR analysis of 6 protein coding genes were carried out.Sequence alignment analysis showed that there were site differences in DNA and c DNA sequences of the six protein coding genes in inbred lines Zheng58 and Chang7-2.Bioinformatics analysis showed that Zm00001d017706 may be related to corn grain development.The results of q RT-PCR showed Zm00001d017703 and Zm00001d017708 may be candidate genes for qhkw5-3,the preliminary analysis of bioinformatics showed that the proteins encoded by the two candidate genes belonged to hydrophilic proteins.These results lay a foundation for the isolation and functional analysis of the gene.