In vitro assessment of the nematicidal potential of Streptomyces violascens strain AS2 against root-knot nematodes (Meloidogyne sp.)

Abstract

Root-knot nematodes (RKNs, Meloidogyne spp.) present a major challenge to sustainable production. The detrimental environmental impacts and increasing resistance associated with synthetic nematicides have increased the need for biocontrol alternatives. Here, we report for the first time the nematicidal properties of Streptomyces violascens and its viability as a safe and effective solution against nematode infestation. In vitro assays showed that aqueous and ethyl acetate extracts of S. violascens significantly impeded Meloidogyne sp?s reproductive and locomotive functions. The aqueous extract displayed remarkable efficacy, completely inhibiting egg hatching at a concentration of 600 ?g/mL, with an LC50 of 168.38 ?g/mL, and causing 99% immobility of second-stage juveniles (J2s) at 800 ?g/mL within 72 h. Conversely, the organic extract exhibited a 29.3% hatching rate (LC50 of 849.26 ?g/mL) and 79% immobility of J2s under comparable conditions. These findings point to the robust nematicidal potential of S. violascens extracts. Enzymatic profiles supported these results, with the selected isolate producing chitinase and protease enzymes capable of degrading nematode eggshells. Our results show that the S. violascens strain can be integrated into a sustainable nematode management practice as an important agent of RKN biocontrol.