Effect of Foliar Application of chitosan and salicylic acid on potato (Solanum tuberosum) yield under low irrigation

In order to investigate the effect of deficit irrigation on vegetative growth characteristics and potato tuber and the effect of foliar application of chitosan and salicylic acid on yield and physiological characteristics of experimental potatoes as a split plot in a randomized complete block design with three replications in 2019 at an agricultural reaearch station in the city of Fariman. Experimental treatments included irrigation levels (60, 80 and 100% water requirement) and foliar application of chitosan and salicylic acid (control treatment, 2 g/l chitosan, 0.5 g/l salicylic acid and combined treatment with chitosan and salicylic acids). Irrigation levels in main plots and foliar spraying treatments were included in sub-treatments. Deficit irrigation treatments were applied 20 days after after plant emergence and at each irrigation period, and foliar application of chitosan and salicylic acid was performed in two stages during the growing season: at the flowering stage (beginning of tuber development), and at the mid-growth stage of tubers. The results showed that by reducing the irrigation volume by 20%, the same performance can be achieved with the performance in full irrigation conditions. Foliar application chitosan and salicylic acid also yielded different results. Foliar application of chitosan prevented a decrease in chlorophyll a concentration as the most important leaf photosynthetic pigment in 80% irrigation treatment. Other pigments showed similar behavior to chlorophyll a in solutions sprayed with chitosan or a combination of chitosan with salicylic acid. Proline, free phenols and soluble carbohydrates as secondary metabolites that undergo stress-induced osmotic regulation of leaf cells also had higher concentrations in chitosan foliar application at 80% irrigation treatment than their control treatment. Foliar application of chitosan and salicylic acid separately or in combination in treatments that were irrigated at 20 and 40% also maintained the concentration of glutathione peroxidase. Despite the above effects, foliar treatments could not clearly have a significant effect on glandular function.It does this by playing an important role in counteracting oxidative stress and balancing oxygen free radicals, as well as its role in protecting cell membranes, especially under stress conditions. According to the results of this experiment, it can be concluded that although these compounds have a significant role in the interaction of potato plant with deficit irrigation conditions, but the time and dose of its use requires more detailed research. Time and dose used that can compensate for the effects of stress and improve yield in deficit irrigation treatments.