RESUMEN
KEY MESSAGE: Genome-wide association on winter survival was conducted using data from image-based phenotyping method. Nine QTL were observed and three of them with candidate gene identified. Winter survival is an essential trait of winter wheat (Triticum aestivum L.) grown in regions with high risk of winterkill. We characterized a diversity panel of 450 Canadian wheat varieties that included mostly winter-growth habit wheats to identify key genetic factors that contribute to higher winter survival under field conditions. To more accurately quantify winter survival differences among varieties, image-based phenotyping methods, captured by unmanned aerial vehicle (UAV) and on ground level, were used to estimate the winter survival of each varieties. Winter survival index was developed to correct for emergence when evaluating winter survival. Winter survival measurement estimated by visual estimation, UAV imagery and ground imagery showed strong correlation with each other and had comparable broad-sense heritability. Genome-wide association studies resulted in the identification of seven quantitative trait loci (QTL) for winter survival including Vrn-A1. By using the recently released annotated sequence of the wheat genome and the available RNA-Seq data, two putative candidate genes underlying the QTL for winter survival were identified. However, our study showed that certain QTL was unique to specific winter survival measurement. Collectively, our study demonstrated the feasibility of using UAV-based imagery for the identification of loci associated with winter survival in wheat. The complexity of in-field condition make our result a valuable complement to indoor frost-tolerance studies in the identification of genetic factors not directly linked to freezing tolerance.