Biocompatibility of Steinernema glaseri with a nematode trapping fungus Arthrobotrys superba on different nutrient media

Abstract

Steinernema glaseri is known to be the most efficacious biocontrol agent against many soil insects belonging to various orders and of diverse habitats. In nature the efficacy of such entomogenous nematodes may be challenged by many micro pathogens. Keeping this in view, the biocompatibility of Steinernema glaseri with a nematophagous fungus Arthrobotrys superba was assessed on eight different nutrient media. The predatory activity of A. superba was evaluated in terms of trap formation, conidiophore formation, and number of adhesive cells formed in the presence and absence of nematodes. The fungus failed to form any trap on any of the culture media in the absence of nematodes. However, in the presence of nematodes, the trap formation by the A. superba was increased and found to be maximum on LNM (low nutrient mineral salt) medium and minimum at WA (water agar) of all the culture media tested. In the present investigation, the effect of CMA (2% and 5%) was not considerable; however, gradually higher dilutions of CMA induced greater number of traps. This less pronounced effect might be due to nutrient richness because low nutrient levels were found to be necessary for the formation of conidial traps. The number of conidiophores decreased with increase in dilution of Corn Meal Agar from 5% to 2%. Higher number of chlamydospores was observed in phenylalanine treated medium which indicates the inhibiting effect of phenylalanine on the growth of A. superba. Our results suggest that richness of soil has pronounced effect on the predatory activity of nematophagous fungus, Arthrobotrys superba which may further affect the biopotential of entomogenous nematode Steinernema glaseri, therefore, care should be taken while releasing entomogenous nematodes in an agroecosystem for managing various insect pests in a more efficient manner.