Medicinal plants present potential to control phytopathogens due to the direct effect or by the activation of defense mechanisms like phytoalexins. Then, the present work had the objective to verify the antifungal and elicitor effect of citronella (Cymbopogon nardus) obtained from methanolic and ethanolic extracts. It was studied the accumulation of phytoalexins in the mesocotyls of sorghum and in cotyledon of soybean, in response to application of fractions from crude extracts methanolic (EME) and ethanolic extracts (EET) of citronella. The EME and EET extracts were fractioned by gel filtration chromatography (CFG) and three fractions were obtained from the methanolic extract (FMI, FMII and FMIII), and two fractions from the ethanolic extract (FEI and FEII). The molecular weight for the FMI, FMII, FMIII, FEI and FEII were 69.29, 40.51, 18.72, 65.89 and 24.11 kDa, respectively. The fractions obtained from the CFG were used in a bioassay of germination of C. lagenarium spores and of induction of phytoalexins in the mesocotyls of sorghum and cotyledon of soybean. There was no significative effect of the fractions EME and EET on germination and appressorium formation by the pathogen. In the accumulation of phytoalexins in soybean cotyledons there was no significant effect of the fractions FMI, FMII, FMIII, FEI and FEII. However, it was detected a significative effect of fractions obtained by CFG on the production of phytoalexins in mesocotyls of sorghum. The highest accumulation of phytoalexin in mesocotyls of sorghum was obtained in the FMI and FMIII fractions, which differed significantly to the control. Based on the obtained results, it is possible to conclude that fractions partially purified obtained from EME of C. nardus present potential to induce phytoalexins in sorghum mesocotyls.
mesocotyls; cotyledon; glyceolin; deoxyanthocyanidin; citronella
