R. Reuveni et al., INDUCTION OF GROWTH INCREASE AND SYSTEMIC RESISTANCE TO EXSEROHILUM-TURCICUM IN MAIZE BY FOLIAR SPRAY OF PHOSPHATES, Journal of phytopathology, 141(4), 1994, pp. 337-346
A single foliar spray of O.1 M solution of phosphate salts on the uppe
r side of maize (cv. 'jubilee') leaves 1, 2 and 3 at the 5-6 fully-exp
anded leaf-stage, 2-4 h before inoculation induced systemic resistance
to northern leaf blight caused by Exserohilum turcicum. Nine days aft
er challenge, protection was demonstrated by 91% reduction in the size
and 69% in the number of E. turcicum lesions developing on leaves 4,
5, 6 and 7. Appropriate mixing of phosphate solution with KOH revealed
that the level of protection was not necessarily dependent on the pH
of the solution. The size and number of lesions decreased to 62% and 5
6%, respectively, 12 days after challenge. There was no damage or chlo
rotic stipling on the induced leaves (1, 2 and 3) as a result of the p
hosphate spray. There were no significant differences in the reduction
in the number or size of the lesions obtained when the foliar spray w
as applied 2-4 h or 1, 3, 6, 8, or 10 days before inoculation. One fol
iar spray of K2HPO4 on leaves 1, 2 and 3 in these intervals before ino
culation, remarkably stimulated growth of inoculated plants, which was
expressed by several parameters. The possible dual use of phosphate s
alts as foliar fertilizers and as resistance-inducing agents is discus
sed