Molecular identification, characterization, variability and infectivity of Indian isolates of the nematophagous fungus Pochonia chlamydosporia

Abstract

Cataloguing and conservation of beneficial native soil biota play a vital role in sustaining a healthy, productive soil capable of supporting a level of plant growth that is normal for a particular soil and climate. Four geographical strains of Pochonia chlamydosporia, a saprophytic fungus antagonistic to plant parasitic nematodes, were isolated from 48 soil samples taken from different crop-soil combinations in Karnataka, India. The strains were designated as PDBC PC, PDBC PC56, PDBC PC57 and PDBC PC69. The four isolates had morphological and molecular (with respect to the ß-tubulin gene) similarity, but differed significantly in their preferences for pH and temperatures for spore germination, mycelial growth, time taken for apparent completion of sporulation and spore production on a corn meal agar medium. The four isolates preferred near neutral pH (6.5-7.7) and moderate temperatures (25-35 oC) for practically important features, viz., spore germination, mycelial growth and spore production and yield. All four isolates showed great pathogenicity (68-78%) to the eggs of Meloidogyne incognita under in vitro conditions. PDBC PC56 and PC57 were the most pathogenic (up to 78% egg infection), with the greatest spore yields and least time for sporulation. Identification and quantification of variability of the isolates of the bio-agent with respect to specific features are important for their use under differing agro-climatic conditions and mass production systems. This is the first report to catalogue biodiversity of P. chlamydosporia in Karnataka and of studies on the variability of isolates.