Derivados de fitormônios na indução de resistência contra o ácaro Oligonychus ilicis (McGregor, 1917) (Acari: Tetranychidae) em Coffea arabica L.

Abstract

The exogenous exposure of plants to phytohormones, such as jasmonic acid (JA) and salicylic acid or their respective products methyl jasmonate (MeJA) and methyl salicylate (MeSA), influence the expression of defenses against herbivores and pathogens. Annual agriculture plants are widely studied and, after elicitors application, either through the liquid in direct contact with the plants or through volatiles, can induce defenses promoting resistance against herbivore arthropods and participating in natural enemies recruitment. However, little is known about the effects of these compounds by direct application and through volatiles in perennial plants such as Coffea arabica L. Considering this gap involving a plant of great economic interest, this work evaluated how coffee plants exposed directly and indirectly (by volatiles) to MeJA and MeSA respond defensively against the red spider mite Oligonychus ilicis. The induction of plant resistance was evaluated through the mite performance bioassay, evaluating the number of eggs per female and through the selection of host plants with dual choice tests. The plants directly exposed to the compounds received a 1.5 mM solution, with drying for 48 hours for the behavioral assays. Exposure to volatiles occurred for 7 days until the behavioral test, through plant-based releasers, containing 200ul of the compound. We analyzed the data with generalized linear mixed-effect models (GLMM). MeJA treatments did not differ significantly in both behavioral trials. The application of MeSA directly on the plants and the exposure to volatized MeSA, did not promote significant differences in the oviposition rate of O. ilicis, but the MeSA applied directly, promoted greater attraction of O. ilicis in the host selection assays. Our results suggest a neutrality of the action of MeJA by direct or indirect exposure on coffee plants, while MeSA has a neutral effect by indirect exposure, but an attractive potential when applied directly. Although the promotion of resistance by elicitors in annual plants is frequently reported in the literature, there is a need to expand studies to perennial plants, aiming at a better understanding of alternative techniques to control agricultural pests and the influence on arthropod-plant interactions.