EFFICIENCY OF OVIDIA ANDINA EXTRACTS IN THE CONTROL OF THE PLANT PATHOGEN RHIZOCTONIA SOLANI

The evaluation of plant extracts as disease suppressive is an option to look for alternative crop health management options. Pillo-pillo (Ovidia andina, Thymelae-aceae) is native to southern Argentina and Chile. O. andina extracts control plant damaging arthropods. Our objective was to evaluate O. andina extracts for the control of the plant pathogen Rhizoctonia solani. Powdered and dried aerial parts were successively extracted by maceration with dichloromethane (CH₂Cl₂) and methanol. Aqueous extract was obtained by decoction of aerial plant parts. The fungus was cultivated on PDA added with CH₂Cl₂ extract (diluted in CH₂Cl₂), methanolic, ethanolic and aqueous extract (diluted in ethanol), and hydrodistillation remaining water (diluted in H₂O), all at 1:10 and 1:100 v/v (controls: CH₂Cl₂, ethanol, water). Pathogen growth was significantly reduced by 1:10 CH₂Cl₂ extract, showing hyphal alterations. When five CH₂Cl₂ extract fractions diluted in CH₂Cl₂ were tested, fraction 5 showed equal efficiency as the whole extract. To evaluate extract effect on fungal colonization of plant organs, beetroot glomerules incubated in R. solani colonized soil were recovered, blotted dry and submerged in 1:10 CH₂Cl₂ extract for 30, 60, 90, 120, or 150 s (controls: water, CH₂Cl₂). Glomerules were again recovered, blotted dry, and incubated on PDA for pathogen emergence. Infection was significantly reduced by extract treatments for 120 s. These results are the basis of future greenhouse experiments and led us to continue with further phytochemical investigation of O. andina. Bioguided fractionation of the extracts will enable us to search for new antifungal compounds.