EFFECTS OF KCL CONCENTRATION ON ACCUMULATION OF ACYCLIC SUGAR ALCOHOLS AND TREHALOSE IN CONIDIA OF 3 ENTOMOPATHOGENIC FUNGI

Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus were grown on Sabouraud Dextrose Agar (SDA) modified with KCl to give a range of water activity (a(w)) from 0.938 to 0.998. Growth of all th ree species was optimal at 0.983 a(w) and growth occurred over the a(w ) range tested. Acyclic sugar alcohol (polyol) and trehalose content o f conidia was determined by HPLC and found to vary with species and a( w). Conidia of B. bassiana and P. farinosus were found to contain tota ls of 1.5% and 2-3% polyols respectively at 0.998 a(w), and double the se amounts at < 0.950 a(w). Conidia of M. anisopliae contained from 5. 7% to 6.8% polyols at each a(w) tested. In conidia of all three specie s the predominant polyol was mannitol. The lower molecular weight poly ols, arabitol and erythritol, were found to accumulate at reduced a(w) . Small amounts of glycerol were present in conidia of each species; < 15% total polyols. Conidia of B. bassiana and M. anisopliae contained about 0.5% trehalose from 0.970 to 0.998 a(w), but only trace amounts below 0.950 a(w). Conidia of P. farinosus contained 2.1% trehalose at 0.998 a(w) and this decreased to < 0-1% below 0.950 a(w). Potential t o manipulate the endogenous reserves of conidia of these biological co ntrol agents to enhance viability and desiccation tolerance is discuss ed