Genetic Analysis of Frost Tolerance in Rapeseed/Canola (Brassica Napus L.)

Abstract

Frost can be detrimental to canola (Brassica napus L.) production. Depending on the severity, the entire field can be killed. Having frost tolerance in canola would benefit growers by allowing them to plant early, utilize early season moisture, and avoid high heat during flowering. However, frost tolerance in canola has not been well studied. A protocol was developed that determined 14 day old seedlings should be acclimated at 4°C for 7 days before being exposed to overnight frost (-4°C) in a small freezing chamber. However, when a larger chamber was used for freezing, the protocol was optimized to -8°C instead. A greenhouse study was conducted on a diverse collection of 231 genotypes and genome-wide association scan (GWAS) was conducted to identify potential genes that were related to frost tolerance or abiotic stress tolerance. Thirty-eight significant single nucleotide polymorphism (SNP) markers were selected based on 10,000 bootstraps and 0.1 percent tail of the empirical distribution. The markers were located on chromosomes A01, A02, A03, A04, A07, A08, A09, A10, C03, C05, C06, C07, and C09. Stepwise regression highlighted a QTL located on chromosomes A02. Another GWAS was done on 147 canola germplasm lines phenotyped under natural conditions. Thirty-eight significant SNPs identified from this study were located on chromosomes A05, A07, A09, C01, C02, C03, C04, C05, C06, C07, and C09. Stepwise regression identified a QTL located on chromosome C04. A protocol was developed to measure the freezing induced electrolyte leakage from leaves of rapeseed/canola. A total of 157 germplasm lines were evaluated for freezing induced (-12°C for 2 h) electrolyte leakage. Thirty-six significant SNPs located on chromosomes A01, A02, A03, A04, A05, A06, A07, A08, A09, A10, C01, C02, C04, C05, C06, C07, and C09 were identified. Stepwise regression identified 10 QTL located on chromosomes A01, A02, A04, A06, A07, C02, C05, C07, C09, and one that could not be assigned. All GWAS studies identified potential genes of interest that were related to frost tolerance, abiotic stress, and transcription factors.