Influences of Na₂SiO₃  on phenolic contents in hullless pumpkinand its resistance to powdery mildew

The contents of phenolic, chlorogenic acids and flavonoid in leaves of resistance and susceptible pumpkin cultivars were determined after those cultivars were treated by sodium silicate solution foliar spray and the inoculation of Podosphaera xanthii. The results indicate that the contents of phenolic, chlorogenic acids and flavonoid in the leaves of Si supplied plants are significantly increased. The contents of phenolic acid in leaves of the resistant pumpkin cultivars of the induction treatments(Si+Px) are higher than those of the control (CK) and the inoculation treatments (Px) in 5 d,7 d and 9 d respectively, the contents of chlorogenic acid in leaves of the resistant pumpkin cultivars of the induction treatments(Si+Px) are higher than those of the CK and the inoculation treatments(Px) in 1 d, 3 d, 5 d, 7 d and 9 d respectively, and the contents of flavonoid in leaves of the resistant pumpkin cultivars of the induction treatments (Si+Px) are significantly higher than those of the CK and the inoculation treatments (Px) in 7 d and 9 d . The contents of phenolic and chlorogenic acids in leaves of susceptible pumpkin cultivars of the induction treatments(Si+Px) are higher than those of the CK and the inoculation treatments (Px) in 5 d, 7 d and 9 d respectively, and the contents of flavonoid in leaves of the susceptible pumpkin cultivars of the induction treatments (Si+Px) are significantly higher than those of the CK and the inoculation treatments (Px) except in 1d. The contents of phenolic (except 7 d), chlorogenic acids (except 7 d and 9 d ) and flavonoid in leaves of the resistant pumpkin cultivars are significantly higher than those of the susceptible cultivars after treated with sodium silicate induction, the powdery mildew disease indexes of resistance and susceptible pumpkin are decreased significantly at 10 d and 15 d after the inoculation.