Induction of resistance to Macrophomina phaseolina in soyben treated with rosemary extract
ABSTRACT Plant extracts may induce resistance mechanisms in plants due to the presence of compounds with eliciting characteristics. The aim of this study was to evaluate the effect of rosemary crude extract at the concentrations 0%; 1%; 2.5% and 5% on the activity of peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase (PAL) in soybean plants inoculated with Macrophomina phaseolina. Samples were collected at 0, 36, 72, 120, 168, 216 and 264 hours after treatment. Considering the samples collected at the collar region of plants, for peroxidase, the highest concentrations of the extract provided two induction peaks. There was a constant increase in polyphenol oxidase activity from 36 to 120 hours after treatment at 5% concentration. For PAL, only the concentration of 5% led to increases 83% to 130% higher at 168 and 216 hours after treatment, respectively. For the activities in the root, peroxidase again showed two increment peaks at 5% concentration; polyphenol oxidase was 426% higher at 5% concentration at 216 hours after treatment and PAL activity showed an increase of 340% at 216 hours after treatment with 5% extract. These results indicate the potential of rosemary extract to induce the activity of defense enzymes in the collar region and in the root of soybean plants.