Symbiotic Bacteria, Xenorhabdus spp. of Entomopathogenic Nematodes:Source of Antifungal Compounds against Four Plant Pathogens

Nematodes that kill the insects are called as Entomopathogenic nematodes (EPNs). These nematodes are in association with symbiotic bacteria (Xenorhabdus spp. and Photorhabdus spp.) which are known to secrete different bioactive compounds and exhibit broad spectrum biological activities viz., insecticidal, antifungal, antibacterial properties. Entomopathogenic nematodes, Steinernema and Heterorhabditis were isolated from soil using Galleria mellonella baited traps at fourteen locations representing different cropping agro-ecosystems in Gandhi Krishi Vignana Kendra campus, University of Agricultural Sciences, Bangalore, Karnataka, India. Bacteria isolated from nematodes were identified as Xenorhabdus spp. and designated as School of Ecology and Conservation one to fourty four. Two symbiotic bacterial cultures, School of Ecology and Conservation-6 and School of Ecology and Conservation-10 were used for in vitro evaluation against four plant pathogenic fungi. These two cultures have shown a good insecticidal activity when tested on second instar larvae of diamond black moth Plutella xylostella L. under in vitro condition, compared to other isolated bacterial cultures. Hence, these cultures were selected to know its fungistatic activity against four plant pathogenic fungi i.e., Fusarium oxysporum (Vanilla), Alternaria solani (Tomato), Sclerotium rolfsii (Brinjal) and Aspergillus niger (Groundnut). SEC 6 culture was found to be best for inhibiting the growth of Sclerotium rolfsii (82.41) followed by Aspergillus niger (51.73), Fusarium oxysporum (48.29) and Alternaria solani (45.10).