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 with 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. One-month-old greenhouse grown plants were subsequently cold-acclimated for two months in an environmental growth chamber prior to phenotyping for freezing survival using a visual damage scale and chlorophyll fluorescence (Fv/Fo). There was reasonable correlation observed between visual damage and chlorophyll fluorescence ratings among the top associated loci; the results indicated that some loci contributed to both freezing damage/tolerance and photosynthetic efficiency. The resulting numerical values for phenotypes were used for association analyses with the identified SNPs. Thirteen significant markers were identified on nine chromosomes for the phenotypes scored, with several showing significance for multiple phenotypes. Twenty-five candidate genes were identified as previously associated with freezing tolerance, photosynthesis, or cold-responsive in canola or Arabidopsis.
Highlights
Canola is an important oilseed crop contributing to the global demand for oil production
At 3 and 7 days after the freezing treatment, plants were phenotyped for chlorophyll fluorescence (Fv/Fo), and at 2 weeks, plants were phenotyped for visual damage
Among the three phenotypic data sets evaluated in this study, correlation coefficients Agronomy 2021, 11, x FOR PEER REV(RIE)Wbetween fluorometer readings taken at three- and seven-days was greate7ro(f02.384) than coefficients observed between the two-week visual damage scores and the three- and seven-day fluorometer readings (0.6 and 0.72, respectively; Table 1)
Summary
Canola is an important oilseed crop contributing to the global demand for oil production. The winter survival of canola is in general low and inconstant in many regions of the northern U.S.A. [3]; limiting yearly winter canola acreage. Winter hardiness in canola requires both cold acclimation and freezing tolerance (intensity and duration) [4]. The process of cold acclimation involves environmentally-induced alterations in cellular constituents [5]. This includes the ability of plants to withstand osmotic dehydration triggered by extracellular ice nucleation that causes water to diffuse from cells [6] and reprogramming of gene expression networks [7,8,9,10], allowing plant tissues to survive periods of freeze/thaw cycles
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