Effects of Heat Stress On Pod Set and Seed Yield of Spring Canola.

Canola (Brassica napus L.) is a cool season crop, and as such is sensitive to high temperature stress during flowering. Heat stress during this period results in yield loss due to abortion of pods. Experiments were conducted in greenhouses and growth chambers to investigate the effects of heat stress on pod abortion in spring canola, and to develop a standard heat stress protocol for further experiments. Plants of a commercial hybrid canola variety were grown in the greenhouse and then transferred to growth chambers for heat stress treatments, which consisted of exposure to one of three temperature regimes (32/20⁰C, 28/20⁰C, or 20/15⁰C day/night), initiated at one of three developmental stages (first flower, 3 d after first flower, or 7 d after first flower) and maintained for 3, 7, or 14 d.  Following heat stress treatments, the plants were returned to the greenhouse until maturity.  A control treatment, where the plants remained in the greenhouse, was also included.  Yield components were determined for the main raceme of each plant.  Compared to the greenhouse control, both the 32/20 and 28/20 treatments produced statistically significant (p<0.05) effects on numbers of viable pods, aborted pods, total pods set, seed yield and seed number, with the magnitude of the effects being dependent on the duration of the stress treatment and the developmental stage at which it was initiated.  However, the 20/15 temperature regime did not significantly affect any of the measured parameters.