Chitinase activity and virulence of different isolates of Beauveria bassiana, Metarhizium anisopliae and Lecanicillium spp.

In order to identify promising isolates with higher chitinase activity, 122 entomofungal isolates comprising of Beauveria bassiana (58), Metarhizium anisopliae (33), Lecanicillium lecanii (15), Lecanicillium attenuatum (11), L. longisporum (3) and L. muscarium (2) isolated from different insect hosts/soils of India were studied. The partially purified proteins from the isolates were subjected to chitinase activity and were estimated by measuring the release of reducing saccharides (one NAGA Unit) from colloidal chitin spectrophotometrically at 582 nm (A₅₈₂). Forty nine isolates of B. bassiana showed chitinase activity ranging from 21 to 182 µg/ml, with the highest enzyme activity by the isolate PDBC-Bb-5a. Thirty three isolates of M. anisopliae exhibited chitinase activity ranging from 23 to 144 µg/ml and the highest (144 µg/ml) was by the isolate Ma-4. Among the 15 isolates of L. lecanii tested, three isolates viz., Vl-7, Vl-24a, Vl-25a had high chitinase activities ranging between 100 and 126µg/ml. Vl-22 isolate of L. attenuatum, Vl-24 of L. longisporum and Vl-8 of L. muscarium showed higher activities (90, 110 and 117µg/ml respectively). Bioassay studies with these isolates on cowpea aphid, Aphis craccivora in glass house indicated higher nymphal mycosis ranging from 72.3 - 83.0%.