Genome-wide association mapping of freezing tolerance in canola (Brassica napus L.)

Authors: Chao, Wun; Horvath, David; STAMM, MICHAEL - Kansas State University; Anderson, James

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2021
Publication Date: 1/27/2021
Citation: Chao, W.S., Horvath, D.P., Stamm, M.J., Anderson, J.V. 2021. Genome-wide association mapping of freezing tolerance in canola (Brassica napus L.). Agronomy Journal. 11(2):233. https://doi.org/10.3390/agronomy11020233.
DOI: https://doi.org/10.3390/agronomy11020233

Interpretive Summary: Canola is an important oilseed crop contributing to the global demand for oil production. Although winter canola generally produces greater yields than spring canola, the range of winter canola is limited by its inability to withstand the winter conditions experienced in many regions of the northern U.S.A. Improving winter hardiness in canola requires knowledge of the many genes that control this trait. Using a genetics approach, we located 32 regions on the chromosomes of winter canola that are associated with freezing tolerance. The numerous genes within these regions could be potential resources for improving freezing tolerance. This knowledge should allow breeders to start integrating freezing tolerance traits into elite breeding lines of both winter- and spring-types of canola, and to increase canola production in the U.S.

Technical Abstract: Winter canola generally produces greater yields than spring canola. However, its range is limited due to its inability to withstand the harsh winter conditions that occur in many northern regions of the U.S.A. To identify loci associated for freezing tolerance in canola, we conducted a genome-wide association study (GWAS) using a genotyped diversity panel containing 399 accessions consisting primarily of winter canola. Genotyping-by-sequencing (GBS) of this canola diversity panel population identified 251,575 single-nucleotide polymorphisms (SNPs). Cluster analysis confirmed a high degree of diversity within the population of accessions, with minimal sub-clustering of genotypes. One-month old plants from this population were phenotyped for freezing survival and chlorophyll fluorescence (Fv/Fo). There was reasonable correlation observed between visual damage and chlorophyll fluorescence ratings among the top associated loci. The resulting numerical values for phenotypes were used for association analyses with the identified SNPs. Thirty-two significant loci were identified for the phenotypes scored, with several showing significance for multiple phenotypes. Thirty-eight candidate genes were identified as previously associated with freezing tolerance, photosynthesis, or were differentially regulated by cold.