M. Reuveni et al., INDUCTION OF SYSTEMIC RESISTANCE TO POWDERY MILDEW AND GROWTH INCREASE IN CUCUMBER BY PHOSPHATES, Biological agriculture & horticulture, 9(4), 1993, pp. 305-315
A single spray of 100 mM solutions of K2HPO4, KH2PO4, Na4P2O7, and Na3
PO4 on the upper surface of the first true leaf of cucumber plants 2h
before inoculation with a conidial suspension of Sphaerotheca fuligine
a, induced systemic protection to powdery mildew in leaves 2 and 3. Ap
plication of Na2HPO4, had little or no effect. A mixture of KH2PO4 and
Na2HPO4, which was sprayed on leaf 1 however, markedly induced system
ic resistance on leaves 2 and 3. Spraying K2HPO4, on leaf 1 at the sam
e concentration at 96,48 and 2h before inoculation induced 74,76 and 9
6%, respectively, of systemic protection in the number of powdery mild
ew pustules per plant as compared to plants sprayed with water. Consis
tently, inductions with K2HPO4, or KH2PO4 were the most effective for
systemic protection. One spray of K2HPO4 on leaf 1, two or four days b
efore inoculation also stimulated plant growth, regardless of inoculat
ion. The possible dual use of phosphate salts as foliar fertilizers an
d as agents for induced resistance is considered.