The Effect of Foliar Nutrition with Potassium Sulfate and Zinc Sulfate on Winter Cold Hardiness of Grapevine Buds cv. Bidaneh Ghermez (Vitis vinifera L.)

Winter cold damage is the main problem in the grape growing regions of Iran. The present study was conducted to investigate the nutritional effect of potassium sulfate and zinc sulfate on winter cold resistance of Bidaneh Ghermez grape buds.   For this purpose, foliar application of potassium sulfate in three concentrations (0, 5 and 10 g.l-1) and zinc sulfate in four concentrations (0, 0.5, 1 and 2 g.l-1) and combined treatments during the growing season on four occasions were sprayed the vines of a commercial vineyard. The measured traits included determining LT50 based on electrolyte leakage and tetrazolium test, soluble sugars, proline content and relative water content of buds.   The results showed that the lowest lethal temperature (LT50) based on two methods of evaluation, electrolyte leakage and tetrazolium test in the control treatments were -16.5 and -15.5 (°C), respectively, while in the foliar treatment of 10 g.l-1 of potassium sulfate with 2 g.l-1 of zinc sulfate were -20 and -19.30 (°C), respectively. The results also showed that the highest soluble carbohydrates and proline content were obtained in 10 g.l-1 potassium sulfate and 2 g.l-1 zinc sulfate, the lowest relative water content of buds in 10 g.l-1potassium sulfate and 2 g.l-1 zinc sulfate alone was observed. The observed biochemical changes observed were correlated with the reduction in LT50.   It seems that the foliar application of K2SO4 and ZnSO4 can simultaneously promote tolerance to winter cold in the grape cv. Bidaneh Ghermez.