Genetic dissection of husk number and length across multiple environments and fine-mapping of a major-effect QTL for husk number in maize(Zea mays L.)

Husk number(HN) and husk length(HL) influence the mechanical harvesting of maize grain. We investigated the genetic basis of HN and HL using a population of 204 recombinant inbred lines phenotypically evaluated in five environments. The two husk traits showed broad phenotypic variation and high heritability. Nine stable quantitative trait loci(QTL) were identified by single-environment mapping, comprising four QTL for HN and five for HL, and three QTL explained >10% of the phenotypic variation. Joint mapping revealed 22 additive QTL and 46 epistatic QTL. Both additive and epistatic(additive ×additive) effects as well as a few large-effect QTL and some minor-effect QTL appeared to contribute to the genetic architecture of HN and HL. The QTL for HN located on chromosome 7, q HN7, which accounted for ～20% of phenotypic variation, was detected in all five environments. q HN7 was fine-mapped to a 721.1 kb physical region based on the maize B73 Ref Genv3 genome assembly. Within this interval, four genes associated with plant growth and development were selected as candidate genes. The results will be useful for improvement of maize husk traits by molecular breeding and provide a basis for the cloning of q HN7.