Oslo and Biggar spring wheats respond differently to controlled temperature and moisture stress

In studying the inconsistent field performance of Oslo spring wheat, Oslo and Biggar were exposed to controlled levels of temperature and moisture stress in growth chamber experiments. Plants were started under low stress with day/night temperatures of 18/10 degrees C and watering to 90% of plant-available water. From 30 d after planting to maturity, temperature and/or moisture stress were applied to one-half of the material by raising day/night temperatures to 30/18 degrees C and watering to approximately 30% of plant available water every 3-4 d. Biggar produced greater root dry matter than Oslo under low temperatures but less under high temperature stress. Moisture stress caused a relatively greater decrease in kernel production in Biggar than in Oslo. Although temperature stress reduced seed set relatively more in Oslo than in Biggar, Oslo was better able to compensate through the grain-filling period. The change in rank of grain yield per plant with increasing levels of stress indicates that Oslo was more tolerant to stress than Biggar.