Antifungal activity of Solanum extracts against phytopathogenic Curvularia lunata

Several species of Solanum produce secondary metabolites with antimicrobial activity. In the present study, the inhibitory activity of Solanum chrysotrichum, S. erianthum, S. torvum and S. rostratum against phytopathogenic Curvularia lunata was determined. Methanol extracts from roots, stems, leaves and fruits were evaluated by the method of mycelial inhibition on agar and the minimum inhibitory concentration (MIC) was determined on a liquid medium. To increase the antimicrobial activity, the combined activity of the most active extracts for each phytopathogen was also determined (a combination of intra and interspecies extracts). The results showed that 12 of the 16 methanolic extracts of Solanum species had antifungal effects against C. lunata. The extracts of S. rostratum and S. erianthum developed the highest activity (~80% inhibition and 28.4 MIC μg . ml–1), even, equal to or greater than, the reference fungicide. The mixture of the active extracts of S. chrysotrichum and S. torvum increased their activity. Various extracts affected the macro and microscopic morphology and most of them reduced the number of conidia of the fungus. This resulted in the capacity to control the vegetative growth and reproduction of C. lunata, the causal fungus of corn leaf spot disease.