Indução de resistência à mancha angular em plantas de feijão

Abstract

Common bean (Phaseolus vulgaris) is a crop of major socioeconomic importance in Brazil, and its productivity can be significantly affected by diseases, particularly angular leaf spot, caused by Pseudocercospora griseola. Given the need for more sustainable management strategies, this study aimed to evaluate the effectiveness of different products as resistance inducers in disease management, as well as to investigate the biochemical and metabolic responses associated with induced resistance in bean plants. Metabolites from Trichoderma asperellum, Trichoderma endophyticum, Trichoderma lentiforme, and Pycnoporus sanguineus were tested, along with pyroligneous extract, a mannan oligosaccharide-based fertilizer (AGROMOS®), a microbial fermentation product based on Saccharomyces cerevisiae, acibenzolar-S-methyl (Bion®), the fungicide azoxystrobin + cyproconazole (Amistar Top®), and a control treatment (distilled and sterilized water). Experiments were conducted in vitro, in a greenhouse, and under field conditions, using the cultivars IPR-Curió and IPR-Uirapuru. In the in vitro assays, the products were incorporated into the culture medium, and the mycelial growth rate index (MGRI) and pathogen sporulation were evaluated. In the in vivo experiments, treatments were applied by foliar spraying, and disease severity was assessed using a diagrammatic scale, with the area under the disease progress curve (AUDPC) subsequently calculated. Biochemical analyses focused on resistance induction by measuring peroxidase and polyphenol oxidase activity at different time points after treatment application, either via foliar spray or seed treatment, in both cultivars, with and without pathogen inoculation. Phaseolin accumulation in bean hypocotyls was also evaluated under the same conditions. Overall, foliar applications did not induce the enzymes assessed, whereas seed treatment with Trichoderma spp. influenced peroxidase activity in the IPR-Curió cultivar in the presence of the pathogen. Phytochemical characterization using gas chromatography coupled with mass spectrometry (GC-MS) revealed metabolic changes in seedlings grown from treated seeds of both cultivars. Differences between cultivars were observed, particularly in relation to unsaturated fatty acids. In general, the results suggest that alternative products can promote metabolic adjustments consistent with mechanisms associated with induced resistance, depending on the genotype and experimental conditions..