Genome-wide association study for frost tolerance in canola (Brassica napus L.) under field conditions

Canola growers in the North Central Region of the United States and Canada are highly concerned about possible early frost. Plants can be killed due to their cells rupture when exposed to a freezing temperature. There are different methods to evaluate frost tolerance including field evaluation. Due to environmental variations, it is difficult to get an ideal condition for frost tolerance evaluation under field conditions. In this study, canola seedlings were grown in a greenhouse for 14 days at 20 °C and cold acclimated for 7–14 days at 4 °C. The acclimated seedlings were placed outside under field conditions based on predicted outside temperature between − 4 and − 8 °C to be exposed to a natural freezing condition. After an overnight freezing exposure, the seedlings were brought back to greenhouse to score the freezing induced seedling damage. The experiment was conducted in a randomized complete black design with two replications, and repeated the trial eight times. A genome-wide association study was conducted on 147 spring, winter, and semi-winter germplasm accessions obtained from 15 countries. A total of 37,111 single nucleotide polymorphism markers were used for the analysis. Three mixed populations with no growth type or geographic patterns were identified. One QTL that explained about 5% of the phenotypic variation and located on chromosome C04 was identified associated with frost tolerance of canola. Five potential genes related to frost tolerance and abiotic stress tolerance were identified.