Home About us MoEF Contact us Sitemap Tamil Website  
About Envis
Whats New
Microorganisms
Research on Microbes
Database
Bibliography
Publications
Library
E-Resources
Microbiology Experts
Events
Online Submission
Access Statistics

Site Visitors

blog tracking


 
Biological Control
Vol.
51, No. 3, 2009; Pages: 346 - 354

Imbibitional damage in conidia of the entomopathogenic fungi Beauveria bassiana, Metarhizium acridum, and Metarhizium anisopliae

Marcos Faria, Ann E. Hajek, Stephen P. Wraight

Cornell University, Department of Entomology, Comstock Hall, Ithaca, NY 14853-2601, USA.

Abstract

When dried organisms are immersed in water, rapid imbibition may cause severe damage to plasma membranes; in unicellular organisms, such damage is usually lethal. This study investigated effects of water activity (dryness) of organisms and immersion temperature on imbibitional damage in three insect pathogenic fungi. Conidial powders of Beauveria bassiana (Bb), Metarhizium anisopliae (Ma) and Metarhizium acridum (Mac) were dried/hydrated to a broad range of water activities (aw) (0.023–0.961) prior to immersion in water at 0.5–33 °C. Imbibitional damage in conidia of each fungus occurred rapidly, with no differences in viabilities observed following immersion for 2 vs. 60 min. Damage increased with decreasing water activity of the conidia and decreasing temperature of the immersion water. Dry (aw 0.333) Metarhizium spp. conidia were highly susceptible to imbibitional damage, with viability declining to 5% after immersion at 0.5 °C and 63% following immersion at 15 °C. Germination of the driest Ma conidia was reduced to 66% after treatment at 25 °C. In contrast, Bb was highly tolerant to damage, with significant reductions in viability (to levels as low as 43–65%) occurring only when dry conidia were immersed at 0.5 °C. Damage was prevented when conidia were slowly rehydrated by humidification prior to immersion and immersion temperature was increased to 33–34 °C; germination of all fungi was 94% under these optimal conditions. However, immersion of the driest Bb, Ma, and Mac powders in warm water (33 °C) also resulted in high viabilities (95%, 89%, and 94%, respectively), and slow-rehydrated conidia also retained high viability (87%, 92%, and 83%, respectively) after immersion in ice-cold water (0.5 °C). Formulation of conidia in pure (non-emulsifiable) paraffinic oil provided considerable protection from imbibitional damage. This study underscores a need for establishing standard protocols for preparing aqueous suspensions of sensitive fungi for both research and commercial applications.

Keywords: Biological control; Microbial control; Mycoinsecticides; Anhydrobiosis; Rehydration; Germination; Sorption isotherm


 

 

 
Copyright © 2005 ENVIS Centre ! All rights reserved
This site is optimized for 1024 x 768 screen resolution