Resistance elicitors and defense response enhancers of maize to Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).
The objective of this research was to assess the potential of abiotic compounds as defense response enhancers in maize using enzymatic quantification and their efficiency in reduction of damages caused by S. frugiperda. The experiment was laid out in a randomized complete block design with six treatments and five replications. The treatments were: T1: positive control (distilled water + infestation); T2: negative control (without product application, uninfested); T3: biofertilizer; T4: acibenzolar-S-methyl (ASM); T5: potassium silicate; T6: potassium silicate + ASM. The treatments were applied in V6 stage of maize plants. After five days, the plants were artificially infested with 2nd instar caterpillars of S. frugiperda. Damage assessments were carried out at 4, 8, 16 and 22 days after infestation using a scale of notes. To evaluate the enzymatic activity, one leaf of each plant was removed at 2, 4, 8, 16 and 22 days after infestation. The largest peroxidase activities were observed at two DAI (days after infestation) using the potassium silicate + ASM (2,344.12 UAE.mg-1 of proteína.min-1) treatment, while the larger polyphenol oxidase activity peaks were observed after treatment with ASM at 22 DAI. The application of potassium silicate + ASM in corn plants can promote peroxidase activity. The polyphenol oxidase activity was increased after application of ASM, whereas the presence of the pest (on positive control) could potentially increase the activity of phenylalanine ammonia-lyase. The applications of ASM alone and potassium silicate + ASM contributed to reduction of the foliar damage level caused by S. frugiperda in corn plants.