title: Effect of nutrition on growth and virulence of the entomopathogenic fungus Beauveria bassiana.
abstract: Three isolates of the entomopathogen Beauveria bassiana along with one strain of Metarhizium anisopliae were cultured on seven media with different carbon/nitrogen (C/N) ratios. The effect of nutrition on virulence of the isolates was evaluated via measurement of colony growth, spore yield, germination speed, conidial C/N ratio and Pr1 (a serine protease) activity. 'Osmotic stress' medium produced the lowest colony growth with low numbers of conidia in all isolates. However, these conidia showed a high germination rate and virulence. However, conidial Pr1 activity was low in some isolates. In most but not in all cases conidia from 1% yeast extract, 2% peptone and low (10 : 1) C/N medium had higher Pr1 activity compared with conidia from other media. However, in some instances we could not conclude that there was a relationship among germination rate, conidial Pr1 activity and virulence. C/N ratio of conidia was statistically different among various media and fungal isolates. Conidia with lower C/N ratio generally produced lower LT(50) (lowest median lethal time) values (more virulent). Insect-passaged conidia from different media had lower C/N ratio compared with similar conidia from artificial cultures. Therefore, they should be more virulent than in vitro produced conidia. As germination rate, conidial Pr1 activity and C/N ratio are independent of host, it seems that host-related determinants such as insect cuticle and physiology and environmental conditions may influence host susceptibility and therefore fungal isolate virulence towards host insects.
authors.affiliation: Department of Biological Sciences, University of Wales, Swansea, UK. s.a.safavi@gmail.com
authors.forename: S A
authors.initials: SA
authors.lastname: Safavi
authors.forename: Farooq A
authors.initials: FA
authors.lastname: Shah
authors.forename: Aziz K
authors.initials: AK
authors.lastname: Pakdel
authors.forename: G
authors.initials: G
authors.lastname: Reza Rasoulian
authors.forename: Ali R
authors.initials: AR
authors.lastname: Bandani
authors.forename: Tariq M
authors.initials: TM
authors.lastname: Butt
mesh_terms: D000818:Animals; D052982:Beauveria / Q000187:drug effects* / Q000254:growth & development* / Q000472:pathogenicity; D002244:Carbon / Q000494:pharmacology; D001517:Coleoptera / Q000382:microbiology*; D003470:Culture Media / Q000494:pharmacology; D009584:Nitrogen / Q000494:pharmacology; D014774:Virulence / Q000187:drug effects
chemical_list: D003470:Culture Media; D002244:Carbon; D009584:Nitrogen