Submitted to: Society of Invertebrate Pathology
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 1995
Publication Date: N/A
Technical Abstract: The development of low-cost methods for producing desiccation tolerant, efficacious propagules of the entomopathogenic fungus Paecilomyces fumosoroseus is a requirement for commercialization. High concentrations of desiccation tolerant P. fumosoroseus blastospores can be obtained in submerged culture, but fewer than 30% dried blastospores remain viable after 2 months' storage at 4 deg C. In order to optimize nutritional conditions for improved blastospore survival during drying and storage, a fast, reliable drying method is required. Three air drying methods for P. fumosoroseus blastospores were tested. Mycelia-free blastospore suspensions were obtained by filtering 4-day-old shake flask cultures with cheesecloth. Prior to drying, blastospore suspensions were centrifuged, rinsed twice with 0.7M polyethylene glycol 200 (PEG) and resuspended in PEG or deionized water. Blastospores were inoculated into silica gel, sand, and diatomaceous earth and dried for 10 seconds, 2 hours, and 9 hours, respectively. The viability of dried blastospore preparations was determined by plating blastospores rehydrated in 0.4M PEG on potato dextrose agar. When P. fumosoroseus blastospores were dried on silica gel, 3% (SD=1.25) of the blastospores rehydrated in water survived and 11% (SD=4.4) of the blastospores rehydrated in PEG remained viable. In sand, 62% (SD=44) of the blastospores survived drying. A 67% (SD=19) survival rate was observed for blastospores mixed with diatomaceous earth and dried at a controlled humidity of 70% for 9 hours. While the reliability of the silica gel and diatomaceous earth drying methods was similar, drying on silica gel is a faster and a more stringent test of desiccation tolerance.