The effect of methanol foliar application on yield and physiological traits of cowpea under water deficit stress

In order to evaluate the effect of methanol foliar application on yield and physiological traits of cowpea under water  deficit the experiments were carried out in the research farm of Safiabad Agricultural and Natural Resources, Research and Education (Dezful) along two crop years 2016-17 and 2017-18. The experiment was performed as split split plots in a randomized complete block design with three replications. The studied treatments included water stress at four levels (25, 50, 75 and 100% water supply of the plant) as the main plot, three levels of methanol foliar application (control, 10 and 20% by volume) as a secondary factor and two bean genotypes (1057 line omidbakhsh and Mashhad) were as a sub-factor. The results showed that the application of different levels of water stress reduces the relative water content of leaves, the amount of chlorophylls and carotenoids and increases the amount of electrolyte leakage and proline content. On the other hand, foliar application of different levels of methanol were able to reduce greatly the destructive effects of water  deficit so that the relative water content of leaf increased from 69% in control to 73% in 20% volumetric methanol. Also, 1057 line showed better conditions than Mashhad cultivar for all measured physiological traits and was better in ability to tolerate water deficit. In addition, harvest index and biological yield were reduced under water deficit condition, but grain yield at 50% water supply of the plant showed the highest value due to the earlier entry of the plant in this stress to the flowering stage and longer this stage compared to 75% and 100% water supply of the plant. Also, methanol foliar application was able to eliminate the destructive effects of water deficit on the measured yield traits.