The Effect of High Temperature Stress on the Seed Filling Rate and Duration of Three Winter Wheat (Triticum aestivum L.) Cultivars [Armour, Jagger, and Karl 92].

One of the major causes of yield loss in winter wheat growing regions is from post anthesis heat stress. Temperatures around or above 32 degrees C can effect wheat yield by shortening the seed filling duration or the amount of time the plant can remobilize stored carbon to the seed. Wheat plants can partially over come the shorter duration by increasing the rate at which carbon is translocated but only to a point. The objectives of this study were to compare the changes and differences in the seed filling rate and duration of three cultivars of winter wheat during post anthesis heat stress. The experiment was a randomized complete block design with a split-split-plot treatment arrangement. The whole plot treatment was 4 growth chambers two of which were set at an optimum temperature of 25/18 C (day/night) and the other two were used as heat stress at a temperature of 35/28 C (day/night). The sub-plot was three cultivars of winter wheat Armour, Jagger, and Karl 92. The wheat was sown and grown under optimum conditions until after anthesis, when heat stress was applied and maintained until the conclusion of the experiment. The sub-sub-plot was 12 harvest times during seed fill on a 3, 5, 7, 9, 11, 15, 19, 23, 27, 31, 35, and 40 days after heat treatment (DAT). Harvest time intervals were replicated 6 times for each cultivar. Under optimum temperatures during seed fill, all cultivars had a similar positive linear increase in average seed weight across all harvest times. However during heat stress seed weight responded in a rapid linear increase followed by a plateau, at which point, little to no increase was observed. For the three cultivars, Jagger had the fastest increase in seed filling rate and the highest overall average seed weight followed by Karl 92 and then Armour.