Nematoxins of microbial origin: Their identification, characterization and development as bio-nematicides I. isolation and screening of bacterial strains for nematoxicity

A total of 133 bacterial strains were isolated from different sources viz., nematode-infested green-house soil, moss, entomopathogenic nematodes, root-knot nematode females, rhizoplane of fruit trees, and forest soil. Cultures and cell-free culture filtrates (CFs) of all 133 bacterial isolates at three different dilutions were tested under aseptic conditions in lab against Meloidogyne javanica second stage juvenile (J2) mortality. Sixteen isolates showing nematode mortality of ca. 50% at lowest dilution were selected. The short-listed 16 isolates were further subjected to lab assays for confirmation of results and finally only four isolates identified as Providencia rettgeri (two),Pseudomonas putida, Providencia rettgeri, Vibrio sp. were selected on the basis of comparatively higher nematode mortality attributes. The selected four isolates were also tested for their influence on hatching of M. javanica eggs. After 15 days, all the four isolates were at par and reduced hatching from 27 to 30% (CFs) and 20 to 29% (Cultures).No correlation could be established between the metabolic secretions of bacterial strains and nematoxicity.