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

M. Nagesh, S. S. Hussaini, B. Ramanujam, R. Rangeswaran


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.

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