Molecular characterization and study of abiotic soil parameters to understand the natural habitat preference of entomopathogenic nematode Distolabrellus veechi isolates

A survey was carried out to find out indigenous species of nematodes having parasitic properties. Extraction of nematodes was done through insect baiting and White trap method. DNA sequencing of 18S rRNA was done to reveal the identity of this nematode. Moreover, Phylogenetic tree analysis of sequences with existing known sequences revealed that the nematode was Distolabrellus veechi Isolate KPI. A total of 268 samples were collected during 2013–2016 out of which 31 (11.57%) soil samples were found to be positive for the presence of entomopathogenic nematodes. Twelve different sampling areas were chosen for the present study. The search was started randomly but later on more soil samples were collected from places which showed more positive samples. The preference for habitat might be due to difference in chemical ecology of soil dwelling nematodes. Considering this, a detailed physico-chemical analysis of each and every sample was done. The parameters studied were, Electrical Conductivity, pH, sand, silt, clay, moisture, water holding capacity, carbon, nitrogen, hydrogen, calcium, magnesium, sodium and potassium. A comparative study was done and correlated with presence or absence of nematodes. Among different habitats, river catchment area was the most preferred site where as road and railway tracts were least preferred. Moreover, most preferred site showed highest values of sand and nitrogen content. On the other hand, least preferred site showed highest value of EC, Ca and carbon where as it showed lowest value of pH, silt and sodium. But nematode presence showed significant correlations with pH (r=0.582*), sand (r=0.712**) and Magnesium (r=-0.633*).