Inhibition Effect Of Powdery Mildew Development By Foliar Spray Dipotassium Phosphate And So On To Summer Squash (Cucurbita Pepo L.)

The aim was to explore the comprehensive measures of inhibiting powdery mildew to summer squash. Taking Chunyu No.5（Resistance）, Saina（susceptibility）, Chunyu No.4（susceptibility）, 23, 26, NS1402, NS1404, NS1405 and so on as test msterials, at two trial points of Yangling and Taibai, the inhibition effect to powdery mildew, the plant yield and soluble protein content and soluble sugar content were investigated by foliar spray 5 g/L NaHCO₃, 5.706 g/L K₂HPO₄(PH 9.3, 2.62 g/L K₂SiO₃（PH 9.3）, RM: 0.188 g/L Riboflavin + 0.746 g/L Methionine and distilled water used as blank control, the physiological and biochemical mechanism of resistance and susceptibility to powdery mildew of summer squash were discussed briefly. The main results of the study were as following:1. After foliar spraying 5 g/L NaHCO₃, 5.706 g/L K₂HPO₄, 2.62 g/L K₂SiO₃ and RM, the inhibition effect to powdery mildew of summer squash was 5.706 g/L K₂HPO₄>5 g/L NaHCO₃>2.62 g/L K₂SiO₃>RM. On the whole, the best treatments were NaHCO₃ and K₂HPO₄. To a certain degree, the four kinds of inducer treatment could postpone effectively the summer squash incubation period of the powdery mildew, and promoted plant growth.2. After treatments, the individual plant yield of summer squash did not have regularity obviously, while the plant yield was higher than control and over all, the effect of 5.706 g/L K₂HPO₄ and RM treatment was better, followed by 2.62 g/L K₂SiO₃. Plant yield added was positively correlated to increasing resistance, the correlation coefficient was 0.693.3. The soluble protein content and soluble sugar content of summer squash leaf were affected by treatments. The measures induced the summer squash own stress reaction and formation of powdery mildew resistant mechanism by adjusting the endogenous type and content of nutrients. Soluble sugar content increased was positively correlated to increasing resistance, the correlation coefficient was 0.754.4. Taking molecular markers lingked to resistance genes in our germplasms, of which, 15 germs contained dominant resistance gene Pm1, from which 13 materials were moderate resistance, so the coincident rate of PCR and the field survey result was 86.67%; 11 materials contained dominant resistance genes ZYMV-2, the coincident rate of PCR and the field survey result was 100%; none of germplasms contained resistance genes ZYMV-1. The material No.28 contained resistance genes Pm1 and ZYMV-2. Based on obove results, molecular markers ZY-136, ZY-138 and ZY-157 could be applied to our breeding materials.