Genome-wide Association Study Reveals a NAC Transcription Factor TaNAC074 Linked to Pre-harvest Sprouting Tolerance in Wheat

Twelve QTL associated with pre-harvest sprouting tolerance were identified using association analysis in wheat. Two markers were validated and a candidate gene TaNAC074 for Qgpf.cas-3B.2 was verified using Agrobacterium-mediated transformation. Pre-harvest sprouting (PHS) is a considerable global threat to wheat yield and quality. Due to this threat, breeders must identify quantitative trait loci (QTL) and genes conferring PHS-tolerance (PHST) to reduce the negative effects of PHS caused by low seed dormancy. In this study, we evaluated a panel of 302 diverse wheat genotypes for PHST in four environments and genotyped the panel with a high-density wheat 660 K SNP array. By using a genome-wide association study (GWAS), we identified 12 stable loci significantly associated with PHST (P < 0.0001), explaining 3.34 - 9.88% of the phenotypic variances. Seven of these loci co-located with QTL and genes reported previously. Five loci (Qgpf.cas-3B.2, Qgpf.cas-3B.3, Qgpf.cas-3B.4, Qgpf.cas-7B.2, and Qgpf.cas-7B.3), located in genomic regions with no known PHST QTL or genes, are likely to be new QTL conferring PHST. Additionally, two molecular markers were developed for Qgpf.cas-3A and Qgpf.cas-7B.3, and validated using a different set of 233 wheat accessions. Finally, the PHST-related function of candidate gene TaNAC074 for Qgpf.cas-3B.2 was confirmed by CAPS (cleaved amplified polymorphic sequences) marker association analysis in 233 wheat accessions and by expression and phenotypic analysis of transgenic wheat. Overexpression of TaNAC074 significantly reduced seed dormancy in wheat. This study contributes to broaden the genetic basis and molecular marker-assisted breeding of PHST.