Comparison of some metabolites alteration in two wheat cultivars subjected to terminal drought stress during grain filling

The aim of this study is to study the effects of water deficit on physiologic parameters related to yield in two wheat cultivars (Triticum aestivum L.), Marvdasht and Zagros (sensitive and tolerant to terminal season drought, respectively) grown in pots under well watered and water-stressed starting from anthesis to maturity. Water stress resulted in a marked increase in leaf proline content of the drought-tolerant that led to alleviate the deleterious effect of water stress whereas, a slightly increment at the end of grain development observed in drought sensitive cv. The effect of drought on grain yield was primarily due to the significant reduction in grain weight, particularly in drought-sensitive. The results indicate that grain filling processes under water restriction are limited by low substrate availability and reduced synthesis capacity of the sink. Hence, the main physiological factor associated with yield stability of Zagros under drought stress may be attributed to the capacity for chloroplast activity in the flag leaf. The higher assimilate in Zagros grains under drought could also be related to drought resistance. These results raise the possibility that water stress-induced elevated levels of proline in Zagros contribute to reduced harmful stress during grain filling.   Key words: Assimilate, flag leaves, grain yield, proline, soluble proteins, wheat (Triticum aestivum L.).