Significance of metabolites of native Xenorhabdus, a bacterial symbiont of Steinernema, for suppression of collar rot and root knot diseases of groundnut

Abstract

Native isolated Xenorhabdus from Steinernema spp. manifest wide variety of secretary proteins, mainly in three clusters having mol wt in the range of 20-21, 46-51 and 60-66 kDa. The proteins of high mol wt, 76-90 kDa, apart from regular proteins are produced only in Xenorhabdus isolates of S. riobrave (SrM & A), but not in the isolates S. carpocapsae (Sc) and S. thermophilum (St). Under pot culture efficacy, average galls/root of groundnut (root-knot index) was significantly low with higher shoot and root wts in exo- and endo-toxic factor (2% v/w) treatments of different Xenorhabdus isolates over control. Effect of Xenorhabdus metabolites against collar rot disease of groundnut revealed that soil application of exo- and endo-toxic metabolites (1:10 diluted) in root zone of plants were effective in suppressing fungus Aspergillus niger, giving better plant height and survival of groundnut at harvest. PCR amplification of genomic DNA showed multiple amplified products of Xenorhabdus isolates (Sr A & M, St)