MUTUAL RELATIONS BETWEEN JASMONIC ACID AND ACIBENZOLARSMETHYL IN THE INDUCTION OF RESISTANCE TO FIRE BLIGHT ERWINIA AMYLOVOROA IN APPLE TREES
W. Warabieda, M. Markiewicz, D. Wójcik, J. Pulawska
Analysis of the effects of jasmonic acid (JA) (at 1.5 mM and 2.5 mM) and acibenzolar-S- methyl (BTH) (at 0.5 mM and 1.5 mM), applied separately or together, on the development of fire blight in ‘Gala’ apple trees showed that in almost all the variants of elicitor treatment the development of fire blight symptoms was lower than in the control. The disease severity in control plants was much higher in the nitrogen-fertilized than in the nitrogen-deficient plants, and the efficacy of the elicitors in controlling the disease was also higher in the N-fertilized plants. The induction of the expression of selected PR apple genes (PR-1a, PR-2, PR-3) by BTH was much more significant than by JA. The studies have shown the existence of mutual relations between JA and BTH in the induction of PR gene expression. These relations depended on nitrogen fertilization, but generally JA was antagonistic to BTH more often than BTH to JA. However, this was not reflected in the severity of the disease symptoms. Analysis of the costs of induced defence showed no effect of the application of the elicitors on shoot growth, fruit yield, or seed weight in apple trees in either fertilization variant.