Assessment of osmoregulation capability in bread wheat (Triticum aestivum L.) cultivars using response of projected pollen grains to drought stress

In this study thirty three wheat cultivars were compared for osmoregulation capability using the ratio of projected pollen grains area under water stress to normal conditions. Digital images of pollen grains obtained from plants grown under well watered condition, were analyzed to obtain their projected areas. Field experimental arranged in a split-plot (cultivars were assigned to sub-plots and drought stress to main plots) in order to compare cultivars grain yield under water stressed and well watered conditions. Based on the results of pollen area ratio, cultivars were divided into two groups. Cultivars, Dez, Kavir, Roshan, Back Cross Roshan (winter type), Zarrin, Pishtaz, Omid and Alvand were classified as capable for osmoregulation as they had a ratio of higher than unit, while the others were grouped as incapable since had ratio lower than unit. Results of ANOVA showed that drought stress and cultivar had significant effects on grain yield and its components as well as biological yield and harvest index. In general, drought stress significantly reduced the grain yield. On the other hand, average grain yield of osmoregulation capable group was 1.73 times greater than that of incapable group. Meanwhile, significant correlation coefficient (r = 0.29**) was found between projected pollen area and grain yield under drought stress condition, implying that increased grain yield could be attributed to osmoregulation capability. Wheat cultivars grouped as capable for osmoregulation are suggested to be used in breeding programs for increasing drought tolerance.