| Popis: |
This study was conducted to test five substrates (whole rice, broken rice, dovme, wheat and burghul) for the mass production of Beauveria bassiana isolate 5-4, known to be affective against stored-cereal pests. A solid-state fermentation technique was used, and amount of product, number of conidia, germination, hydrophobicity and thermotolerance of conidia, and their virulence on Rhyzopertha dominica adults were used to evaluate the success of substrates. For production, 100 g of a substrate was used in a polypropylene bag. After sterilization and inoculation, the bags were sealed and incubated for 14 days at 25ºC. Hydrophobicity was assessed using the aqueous-solvent partitioning method with PM buffer, and liquid paraffin as two phases. Thermotolerance tests were conducted by exposing conidia to 35, 40 and 45°C for 15, 30 and 60 minutes. In virulence test, adults were released into 40 gr wheat mixed with conidia and kept at 25oC and 65% relative humidity in darkness for 14 days. The highest amount of product was obtained by using whole rice (4.10g/bag), followed by broken rice, wheat, dövme and burghul. The highest number of conidia was achieved using broken rice (10.24x1010conidia/g) and whole rice (9.62x1010conidia/g). The germination rates of conidia did not vary significantly. Significantly higher hydrophobicity rate was obtained using wheat (88.73%). The conidia from burghul and wheat showed higher thermotolerance than those from other substrates. The conidia obtained from whole rice and broken rice caused 80.3% and 72.0% mortalities, respectively, significantly higher than the others. Rice was found to be a better choice for this isolate as the ultimate purpose is to suppress pest populations, with awareness of its shortcomings. It was found crucial to test all important characteristics of produced conidia together for assessment of substrates. |
