Molecular and Phenotypic Characterization of Heterorhabditis indica (Nematoda: Rhabditida) Nematodes Isolated During a Survey of Agricultural Soils in Western Uttar Pradesh, India.

Abstract

Entomopathogenic nematodes (EPNs) are important biocontrol agents of insect pests. To increase the availability of locally adapted entomopathogenic nematode isolates for biocontrol programs, a survey of several agricultural soils in Western Uttar Pradesh, India was conducted. Eight hundred and sixty soil samples from the districts Meerut, Bulandshahr, Baghpat, and Bijnor were collected and examined for the presence of entomopathogenic nematodos using the "Galleria baiting method". Steinernema and Heterorhabditis nematodes were recovered. The isolated Heterorhabditis nematodes were molecularly, and morphologically characterized, and their biocontrol potential was evaluated against Spodoptera litura. Finally, the geographical distribution of entomopathogenic nematodes was studied based on the analysis of ITS GenBank records. A small proportion of the collected soil samples were positive for Heterorhabditis and Steinernema nematodes. Twelve soil samples were positive for the presence of Heterorhabditis nematodes, and 29 samples were positive for Steinernema. The Heterorhabditis nematodes were identified as Heterorhabditis indica based on morphological, morphometrical and molecular analyses. No other species of Heterorhabditis were isolated from the soil samples analyzed, suggesting that this species is dominant in the western part of Uttar Pradesh, India. The morphology of the nematode isolates was somewhat similar to the morphology of the H. indica isolate used for the original description of this species, with a notable exception mucrons were present in the hermaphrodite and female specimens we collected, but this structure was not observed in the specimens used for the original description of the species. Principal component analyses (PCA) show small inter- and intraspecific morphological variability between the nematodes species of the "Indica" clade. The insecticide properties of one isolate, CH7, were evaluated against Spodoptera litura, and the results show that this isolate effectively killed this pest under laboratory conditions, demonstrating its potential as a biocontrol agent. This study sets the basis for establishing new biocontrol agents to be used in future pest management programs in India.