Chemical and biological characterization of Salvia discolor exudate for management of phytopathogens and pests

Description

Phytopathogenic fungi, bacteria and pests cause damage to crops, and result in economic losses. Current control of phytopathogens and pests depends on synthetic pesticides resulting in damage to the environment, and increased resistance. Considering these challenges there is more interest in exploring natural sources as safe and sustainable alternatives. The present study aims to characterise chemically and biologically the dichloromethane extract of aerial parts of Salvia discolor Kunth. Phytochemical investigation reveals the presence of one novel clerodane diterpene along with some known compounds [1] [2] [3] 8,3'-dihydroxy-6,7,4'-trimethoxyflavone , 5,7-dihydroxy-3,4'-dimethoxyflavone , divinatorin A [4] and patagonic acid , which were identified through spectroscopic 1D and 2D NMR analysis. Crude extract was evaluated for its antimicrobial potential against various phytopathogenic fungi, bacteria and pests. The extract exhibited MIC values of 500 μg/mL and 1000 μg/mL against Clavibacter michiganensis subsp. michiganensis, and Pectobacterium carotovorum subsp. carotovorum, respectively. In vitro antifungal activity varied across different fungi at concentrations of 5, 100, 250, 500, 750 and 1000 μg/mL. The extract showed complete inhibition of mycelial growth of Phaeomoniella chlamydospora at 1000 μg/mL statistically equivalent to synthetic fungicide and aligned [5] with previous research findings solani. Moderate activity was reported against Phoma betae, Alternaria solani, Stemphylium sp. and Botrytis cinerea. However, the lowest inhibition (<40%) was observed against C. lindemuthianum and F. oxysporum fsp. lactucae race 1. The extract also showed promising results against gray mold disease in post-harvest tomato fruit. Furthermore, bioinsecticidal activity was measured against Tuta absoluta [6] which exhibited an LC50 of 0.013 mg/mL. These results highlight the potential of surface extract of S. discolor as a natural source of new bioactive compounds and management of phytopathogens and pests contributing to sustainable agricultural practices

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