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In vitro evaluation of British Columbia native plant extracts and plant extracts fermented with Saccharomyces cerevisiae to inhibit plant pathogens growth. Hassan, Rawda


The negative impact of agricultural pesticides on the environment are well documented. This in vitro study evaluates the biological activity of seven British Columbia native plant extracts and plant extracts fermented with Saccharomyces cerevisiae, against three plant pathogens of economic importance: Phytophthora infestans, Fusarium sambucinum and Pectobacterium carotovorum. Crude plant extracts and yeast-fermented extracts using simple fermentable media and Saccharomyces cerevisiae were evaluated, while the pathogen growth development was challenged against in vitro treatments. Dry plant extracts were prepared by dissolving 5 mg of crude extract in 2.5 ml of 70% ethanol; then different concentrations were prepared in 96 wells microliter plates and tested against the selected organisms. The 4- way interaction model (yeast, extract, solvent, treatment dilution) was used for the analysis, and the significance of the interaction in the models was tested by a likelihood ratio test. Moreover, 262 combinations out of 480 of either crude extracts, or fermented extracts applied at different dilutions with different solvents (methanol or water) showed growth inhibition in comparison to controls. Arbutus menziesii treatments, including fractions of the crude extract, demonstrated the most diverse levels of growth suppression of all the pathogens. Fermentation has shown great potential for increasing the extract efficacy. In some cases, a combination of the fermentation period and the extract concentration influences the biological activity of specific treatments. Even though treatments that included water as a solvent mixed with the pathogen culture indicated pathogen suppression, when applied as a solvent, methanol showed preferable scales of inhibition. Moreover, results showed that several fermented treatments inhibited pathogen growth, whereas in many cases, the same treatments did not show the same inhibition when they were tested as crude extracts. This was observed with a 24-hour fermentation of water and methylene dichloride fractions of Arbutus menziesii, Maianthemum stellatum extract, and Rubus spectabilis extract applied against F. sambucinum and P. infestans. Further research is encouraged to identify potentially active compounds, but also to evaluate the fermentation treatments and factors influencing the combinations. Plant fermentation may offer a new opportunity in the development of more ecological and safer biopesticides.

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