Improving Growth and Fruit Yield of Watermelon Using Mycorrhizal Fungi and Salicylic Acid under Different Irrigation Regimes

Water scarcity is the main natural limitation for agricultural production in arid and semi-arid regions. The aim of this study was to investigate the effect of mycorrhizal fungi and salicylic acid on yield and quality of watermelon under water stress. For this purpose, a split factorial experiment was conducted with three replications based on a randomized complete block design in two years. Irrigation treatment at three levels of receiving 100%, 80% and 60% of water requirement were placed as the main factor in the main plots. Mycorrhizal fungus in two levels (including no inoculation and soil inoculation by 20 g m-2) along with spraying of salicylic acid in three levels (including 0, 50 and 100 mg L-1) were designated to the subplots. The highest amounts of proline concentration, peroxidase and catalase enzymes activities were recorded in 60% irrigation treatment. Electrolyte leakage decreased by salicylic acid application, though in each irrigation treatment the lowest electrolyte leakage was recorded in 100 mg L-1 treatment of salicylic acid. Electrolyte leakage was significantly reduced by mycorrhizal fungi application. The highest (9.12%) and the lowest (8.08%) level of total soluble solids were recorded respectively in 80% and 100% irrigation treatments. The highest amount of TSS (9.07%) was obtained with mycorrhizal fungi. TSS was significantly increased by 6.70% and 11.20% with 50 and 100 mg L-1 salicylic acid treatments, respectively, compared to the control. The lowest fruit yield (34.76 t ha-1) was obtained when the plants were exposed to 60% irrigation treatment and no mycorrhizal fungus inoculation conditions. Fruit yield increased significantly in the presence of mycorrhizal fungi inoculation across all irrigation treatment levels, with the highest fruit yield (68.82 t ha-1) being obtained when plants were grown under 100% irrigation treatment and mycorrhizal fungi inoculation conditions. It may be concluded that using mycorrhizal fungus as a biofertilizer and salicylic acid as a plant growth regulator can reduce the harmful effects of drought stress and, hence, it can be recommended to increase the fruit yield and quality of watermelon at least in arid-semiarid conditions.