Genome-wide association study of physical and microstructure-related traits in peanut shell

Peanut shell plays key roles in protecting the seed from diseases and pest infestation but also in the processing of peanut and is an important byproduct of peanut production. Most studies on peanut shell have focused on the utilization of its chemical applications, but the genetic basis of shell-related traits is largely unknown. A panel of 320 peanut (Arachis hypogaea) accessions including var. hypogaea, var. vulgaris, var. fastigiata and var. hirsuta was used to study the genetic basis of two physical and five microstructure-related traits in peanut shell. Significant phenotypic differences were revealed among the accessions of var. hypogaea, var. hirsuta, var. vulgaris and var. fastigiata for mechanical strength, thickness, three scleren-chymatous layer projections and main cell shape of the sclerenchymatous layer. We identified 10 significant single nucleotide polymorphisms (SNPs) through genome-wide association study (P< 5.0 x 10(-6)) combining the shell-related traits and high-quality SNPs. In total, 192 genes were located in physical proximity to the significantly associated SNPs, and 11 candidate genes were predicted related to their potential contribution to the development and structure of the peanut shell. All SNPs were detected on the B genome demonstrating the biased contribution of the B genome for the phenotypical make-up of peanut. Exploring the newly identified candidate genes will provide insight into the molecular pathways that regulate peanut shell-related traits and provide valuable information for molecular marker-assisted breeding of an improved peanut shell.