Fine mapping of a kernel length-related gene with potential value for maize breeding

Kernel size is a major determinant of yield in cereals. Kernel length, one of the determining factors of kernel size, is a target trait for both domestication and artificial breeding. However, there are few reports of fine mapping and quantitative trait loci (QTLs)/cloned genes for kernel length in maize. In this project, a novel major QTL, named qKL9, controlling maize kernel length was identified. We verified the authenticity and stability of qKL9 via BC2F2 and BC3F1 populations, respectively, and ultimately mapped qKL9 to an similar to 942-kb genomic interval by testing the progenies of recombination events derived from BC3F2 and BC4F2 populations in multiple environments. Additionally, one new line (Mc(qKL9-A)) containing the similar to 942-kb segment was screened from the BC4F2 population. Combining transcriptome analysis between Mc(qKL9-A) and Mc at 6, 9 and 14 days after pollination and candidate regional association mapping, Zm00001d046723 was preliminarily identified as the key candidate gene for qKL9. Importantly, the replacement in the Mc line of the Mc's alleles by the V671's alleles in the qKL9 region improved the performances of single-cross hybrids obtained with elite lines, illustrating the potential value of this QTL for the genetic improvement in maize kernel-related traits. These findings facilitate molecular breeding for kernel size and cloning of the gene underlying qKL9, shedding light on the genetic basis of kernel size in maize.

Automated summary

Kernel size is a crucial factor affecting yield in cereals, with kernel length being a key determining factor. A novel major QTL, qKL9, controlling maize kernel length was identified and confirmed through various population tests. This QTL shows promising potential for genetic improvement in maize kernel-related traits.