Evaluation of the activity of Salvia interrupta extracts against Botrytis cinerea on tomato

Description

Phytosanitary defense encompasses a set of techniques aimed at protecting crops from pests. In the last decades, the optimism generated by the widespread and indiscriminate use of synthetic phytosanitary products has been tempered. Today, more environmentally friendly methodologies are gaining ground, such as integrated pest management and organic farming [1]. In the last century, it has been recognized that plant secondary metabolites play a fundamental role in plant ecophysiology. They have both a defensive role against pathogen attacks and an attractive role for beneficial organisms such as pollinators or symbionts. Thanks to these characteristics, several secondary metabolites have found application as effective starting points for discovering new phytosanitary agents [2]. Salvia is the largest genus of the Lamiaceae family, consisting of about 980 species. Salvia spp. contain many health-promoting phytochemicals among which polyphenols, flavonoids and terpenes [3]. For this reason, in this study, we evaluated the effectiveness of two different extracts (called "exudate" and "matrix" respectively) of S. interrupta against Botrytis cinerea, a pathogenic fungus responsible for gray mold, which causes extensive damage to a wide range of crops. Exudate was obtained immerging fresh sage leaves in dichloromethane for twenty seconds, to obtain the isolation of the leaf surface constituents, while matrix was the result of methanol extraction of the previously used dried leaves. The test was conducted in semi-vivo mode, on artificially infected tomato fruits, with the aim of analyzing the effectiveness of extracts at different concentrations (100, 500 and 1000 ppm). For this purpose, an incision was made on tomato fruits, subsequently treated with S. interrupta extracts. Then, the lesion was inoculated with Botrytis cinerea. The commercial products Teldor plus (fenhexamid 42,7%) and Switch (cyprodinil 37.5% + fludioxonil 25%) were used as reference standards. Results showed that both exudate and matrix have significant bioactivity. A clear dose-dependent trend emerged between 100 and 500 ppm. However, at 1000 ppm, a reduction in efficacy was observed, presumably due to phytotoxicity effects. Based on these first observations, S. interrupta appears to possess activity against B. cinerea, and deserves further study.

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