Selection of improved Beauveria bassiana (Bals.) Vuill. strains based on 2-deoxy-D-glucose resistance and physiological analysis

A series of 2-deoxy-D-glucose resistant mutants was obtained from wild type Beauveria bassiana 88 (Bb 88) by UV irradiation. Five mutants were characterized on Sabouraud Dextrose Agar and Chitin Agar for both radial extension rate (V-r) and specific growth rate (mu). These values were obtained after adjusting morphometric data to a mathematical model used for filamentous fungi. Additionally, the protease and lipase potency index, conidial size, viability, and production levels were analyzed. The highest values for those physiological measurements were obtained by mutant 882.5 which, relative to Bb 88, showed a 30% reduction in half-life (LT50) on Sphenarium purpurascens, 70% on Acheta domesticus, and 71% oil Tenebrio molitor larvae and adults. The half lethal concentration (LC50) on T. molitor larvae was 2.8 x 10(5) conidia/mL (con/mL) and 1.5 x 10(6) con/mL, respectively, for mutant 882.5 and Bb 88. This demonstrates that mutant 882.5 is more virulent, with up to an 80% reduction in LC50. This work provides a convenient method for improving strains to be used in biocontrol as a suitable alternative to transgenic constructs. (C) 2009 Elsevier Inc. All rights reserved.