R. Reuveni et al., FOLIAR SPRAY OF PHOSPHATES INDUCES GROWTH INCREASE AND SYSTEMIC RESISTANCE TO PUCCINIA-SORGHI IN MAIZE, Plant Pathology, 43(2), 1994, pp. 245-250
A single foliar spray of 0.1 M phosphate salts solution was applied to
the upper side of maize (cv. Jubilee) leaves 1, 2 and 3 at the five-
to six-leaf stage, 2-4 h before inoculation with Puccinia sorghi. This
treatment induced systemic resistance against common rust as expresse
d by 98% reduction in the number of pustules of P. sorghi developed on
leaves 5, 6 and 7. There was no damage or chlorotic stippling on the
induced leaves (1, 2 and 3) as a result of the phosphate spray. A less
effective, but still significant, reduction (90%) in the number of pu
stules was obtained when the foliar spray was applied 6 days before in
oculation. One foliar spray of K2HPO4 on leaves 1, 2 and 3, 6 days bef
ore inoculation: stimulated plant growth regardless of inoculation. Th
e foliar spray on the day of inoculation was less effective in stimula
ting growth. Appropriate mixtures of phosphate solutions revealed that
the level of protection was not necessarily dependent on the gradual
changes in the pH of the solution. The possible dual use of phosphate
salts as foliar fertilizers and as agents for induced resistance is di
scussed.