Evaluation of drought stress on molecular and morpho-physiological traits of wheat cultivar

Evaluation of molecular and morpho-physiological traits of wheat such as grain yield, grain yield component, growth index values and the expression of some genes in the pathway of drought tolerance, including TaNAC67 and TaMYB73 in the farm of Kurdkoi Agricultural Research Center by split plots with randomized complete blocks design in four replications in this reserach was studied. Drought treatment includes levels of -0.3 (field capacity as a control treatment), -2 and -4 were considered as a main factor and bread wheat cultivars (Baharan, Ehsan, Kalate and Marwarid) as a sub factors. Rain shield was used to control rainfall. Traits such as leaf area (LA), dry matter, crop growth rate (CGR) and relative growth rate (RGR) as well as spike length, thousand grain weight, plant height and grain yield were measured. To evaluation of TaNAC67 and TaMYB73 genes expression, RNA was extracted from the leaves and Real time PCR technique was used. The results showed that all investigated morphological traits decreased under the drought stress. Baharan cultivar had the highest grain yield in the control treatment, but by increasing stress, the largest decrease in grain yield occurred in this cultivar. In case of gene expression evaluation, Ehsan cultivar can be introduced as a cultivar with high drought tolerance. Analysis of variance showed that effect of stress, variety and interaction effect between stress and variety on plant height, spike length, thousand grain weight and grain yield were significant at the probability level of 1% but block effect was not significant for any of studied traits. Comparison of average for drought stress on plant height, spike length, thousand grain weight and grain yield of cultivars showed that these traits decreased by increasing drought stress intensity. Comparison of average for variety and interaction effect between stress and variety on plant height, spike length and thousand seed weight showed that the Ehsan variety had the highest amount of these traits and it has significant difference with the other three varieties. Comparing of average for cultivar and interaction effect between stress and variety on grain yield trait showed that Baharan cultivar had the highest value and it has significant difference with other cultivars. The results of leaf area and dry matter showed that the Baharan variety has the highest sensitivity to drought stress and this sensitivity was higher in the pollination stage than other stages. Relative growth rate results showed that decreases rate of this index in Kalate variety was lower than other varieties. The results of evaluating the growth rate of the crop under drought stress conditions showed that cultivars had different reactions. The results of TaMYB73 and TaNAC67 genes expression under drought stress conditions showed increase in expression for -2 than the control in all cultivars but with the increase of stress intensity from -2 to -4, different cultivars showed different expression levels for the expression of these genes. In the condition of drought stress -4, only cultivar Ehsan showed increase of gene expression for TaMYB73 compared to the control and stress -2 times, and it had a significant difference with other cultivars. Also, the highest expression of TaNAC67 gene in -4 stress conditions was for the kalate variety.