Activity of Aqueous Extracts from Native Plants of the Yucatan Peninsula against Fungal Pathogens of Tomato In Vitro and from Croton chichenensis against Corynespora cassiicola on Tomato.

Abstract

Plant extracts are a valuable alternative to control pathogens of horticultural crops. In the present study, four species of pathogenic fungi were isolated from leaf spots on Solanum lycopersicum and identified by traditional and molecular techniques as Alternaria alternata ITC24, Corynespora cassiicola ITC23, Curvularia lunata ITC22, and Fusarium equiseti ITC32. When 11 aqueous extracts from eight native plants of the Yucatan Peninsula were tested against the four fungi in vitro, the extract from Croton chichenensis roots was most active, inhibiting mycelial growth (79-100%), sporulation (100%), and conidial germination (71-100%) at 3% (w/v). A logarithmic-diagrammatic scale of the pathosystem C. cassiicola-S. lycopersicum was established and used to assess disease severity on inoculated tomato plants in a greenhouse after treatment with the aqueous extract from C. chichenensis roots at 12% (w/v). After 21 days, the disease severity was 57% lower than on the control without extract applied. This dose of the extract was not phytotoxic to tomato leaves and was compatible with the beneficial organisms Bacillus subtilis CBCK47 and Trichodema asperellum Ta13-17. The antifungal efficacy of C. chichenensis is highly promising for incorporation into integrated disease management of tomato crops.