Unveiling the nematotoxic effect of Streptomyces spp. against the root-knot nematode, Meloidogyne enterolobii in guava

Abstract

Guava production in India faces significant challenges due to the invasion of the root-knot nematode Meloidogyne enterolobii. Biological control using metabolite-producing Streptomyces spp. offers a better alternative to synthetic nematicides for managing nematode populations in soil and roots. The native Streptomyces rochei isolated from nematode suppressive guava rhizosphere demonstrated complete inhibition of M. enterolobii egg hatching (100%) and juvenile mortality (100%) compared to other native species. Further, secondary metabolites produced by S. rochei were profiled using gas chromatography/mass spectrometry (GC/MS) analysis and molecular docking experiments were carried out with the key protein Me col-1 (collagen gene) of M. enterolobii. Notably, bioactive compounds of S. rochei such as oxymatrine, melezitose, 2(3H)-furanone, 5-hexyldihydro, 2-nonadecanone 2, and cyclohexane exhibited nematicidal activities. Among them, oxymatrine (− 6.7 kcal/mol), melezitose (− 6.5 kcal/mol), and 2(3H)-furanone (−4.4 kcal/mol) showcased the highest binding affinity against Me col-1. A glasshouse experiment was conducted to study the nematode suppressive effect of cell-free culture filtrate extracts of S. rochei GA, Streptomyces spp. GHS-3 and GHRS-5 on guava seedlings inoculated with M. enterolobii. Guava plants treated with S. rochei GA suppressed M. enterolobii parasitism with a 79.1% reduction in the number of egg masses, and promoted plant growth by 75%. This study highlights the nematotoxic potential of biomolecules produced by S. rochei GA as a promising alternative to synthetic nematicides for the management of M. enterolobii.