Cool Pea Leaves: Canopy Traits to Reduce Heat Stress.

Heat stress in pea can occur when daytime air temperatures exceed 29°C to 32°C during vegetative and reproductive growth, and heat stress lowers yield.  Irrigation or soil moisture availability appears to increase the temperature threshold to >32°C before heat stress occurs.  When soil moisture is sufficient for crop evapotranspiration, crop canopies are usually cooler than daytime air temperatures.  To date, our heat research has used daytime maximum temperature as a reference, but we know little of the actual canopy temperatures experienced by the crop.  Our first objective was to characterize actual canopy temperatures in relation to air temperatures associated with heat stress.  Our second objective, and ultimate goal, was to seek potential heat resistant parents through maintained cool canopy temperatures using traits such as leaf cuticular wax, leaf pigments, leaf size and shape, leaflet and stipule shape, and diameter of tendrils, peduncles and stems.  In 2013 we sampled a 16 cultivar trial and the 94 diverse cultivars from the Pea Association Mapping Panel at two locations in Saskatchewan for leaf size, pigments and wax.  Several times during reproductive growth canopy temperatures from plots were measured with a handheld Infrared thermometer.  Preliminary results of wax and leaf traits will be presented with canopy temperature and yield.