An enriched oxygen atmosphere increases the quality of conidia of both strains of I. fumosorosea, with a variable effect on conidium production.

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The aim of the present work was to study the effect of moisture content and inoculum on the growth and conidia production by Beauveria bassiana on wheat bran (WB)

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White grub larvae are important soil-dwelling pests in many regions of Mexico as they attack many important crops such as maize. The use of synthetic chemicals is currently the main control strategy, but they are not always effective; thus, other alternatives are needed. Microbial control using entomopathogenic fungi represents an important alternative strategy, and species within the genera Beauveria and Metarhizium are considered amongst the most promising candidates. Seventeen Beauveria spp. and two Metarhizium spp. isolates were obtained in surveys of white grub larvae from different regions of Guanajuato, Mexico. All isolates were capable of infecting healthy larvae of the white grub Phyllophaga polyphilla in laboratory assays, but mortality never exceeded 50 %. Isolates were identified using morphological and molecular methods. Based on elongation factor1-α and ITS partial gene sequence data, all Beauveria isolates were identified as Beauveria pseudobassiana. Elongation factor1-α and β-tubulin sequence data identified the Metarhizium isolates to be Metarhizium pingshaense. In contrast, three additional Metarhizium isolates obtained the previous year in the same region were identified as M. pingshaense, Metarhizium anisopliae and Metarhizium robertsii. Microsatellite genotyping showed that all B. pseudobassiana isolates were the same haplotype. Enterobacterial Repetitive Intergenic Consensus fingerprinting information confirmed no significant variation amongst the B. pseudobassiana isolates. The ecological role of these isolates and their impact on white grub larvae populations are discussed.

The secretion of hydrolases by Beauveria bassiana is a main factor in the degradation of cuticle, while in filamentous fungi the resistance to 2-deoxy-Dglucose (2DG) is related to enzymatic deregulation. A series of 2DG-resistant B. bassiana strains were classified according to the phenotypes of germination (G) and radial growth rate (U r ), in addition to their virulence parameters on Tenebrio molitor. This analysis allowed distinction between mutants with greater (881.2) and lesser (884.5) G and U r values, relative to the wild-type strain (88), which correlated with virulence parameters including maximal mortality (M) and time to reach 50% mortality (LT 50 ). Subsequently, using the cuticle of T. molitor as the substrate for these strains, an enzymatic analysis (total proteases, Pr1, chitinases and b-N-acetylglucosaminidase) showed that the contrasting virulence traits were associated with different deregulation patterns: higher specific activities (up to 100%) for the more virulent mutant 881.2 and lower enzymatic levels for mutant 884.5, specifically chitinases (33% reduction), relative to the wild-type strain (88) for both mutants. The differences in cuticle-degrading enzymes were consistent with the appearance of hyphal bodies within infected insects. This is the first study describing the altered enzymatic profiles in 2DG-resistant mutants of B. bassiana with practical implications in the selection of improved strains for biological control.