Metabolic Biomarkers Associated with Heat Stress Tolerance in Spring Canola (Brassica napus L.).

Heat stress significantly impacts the metabolome of many plant species and inhibits the yield potential of economically important cool-season crops such as spring canola (Brassica napus L.). An untargeted metabolomics analysis of the spring canola metabolome under heat stress was conducted to determine if potential biomarkers could be discovered that are associated with heat stress tolerance. Two groups of spring canola that exhibited distinct responses to heat stress were classified as heat tolerant or heat susceptible. The genotypes, four within each classification, were grown in a greenhouse (22-23 / 19-20 C day/night) and then transferred to a growth chamber, just prior to anthesis, where they were exposed to either a control treatment (22/10 C day/night) or a heat stress treatment (31/14 C day/night) for 14 days. The plants were then transferred back to the greenhouse for the remainder of their life cycle. Following the 14 day treatment, unopened floral buds were sampled and lyophilized. Metabolite identification was completed using gas chromatography-mass spectrometry. The experiment was conducted twice and the data analyzed separately to determine reproducibility. Principle component analysis (PCA) showed a significant impact of heat stress on the floral bud metabolome. From the PCA of the heat treated plants in the second experiment, 25 metabolites (loadings) were identified that distinguished the tolerant and susceptible genotypes. These same 25 metabolites were effective at discriminating between the tolerant and susceptible genotypes in both experiments independently. Of the 25 metabolites identified, 8 increased in the tolerant genotypes compared to the susceptible genotypes and 17 metabolites declined in the tolerant genotypes compared to the susceptible genotypes. These data support the hypothesis that metabolites have the potential to be used as biomarkers in the identification of heat stress variation in spring canola.