Trakya University Journal of Natural Sciences (Apr 2017)
DETERMINATION OF CONTROL POTENTIALS AND ENZYME ACTIVITIES OF Beauveria bassiana (BALS.) VULL. ISOLATES AGAINST Tetranychus urticae KOCH (ACARI: TETRANYCHIDAE)
Abstract
Broad host range of entomopathogenic fungi may have a commercial advantage for biological control industry. In addition, all entomopathogenic fungi rely on a combination of different enzymes to penetrate their hosts and these enzymes play an important role in the host range of fungal isolates. The aim of this study is to determine the potential of three Beauveria bassiana (Bals.) Vull. isolates in control of Tetranychus urticae Koch (Acari: Tetranychidae) and to determine their lipase, chitinase, and protease activities. For this purpose, B. bassiana (PaF04, PaF09 and PaF76) isolates, which was previously demonstrated to have entomopathogenic activity against Coleoptera, Lepidoptera, and Hymenoptera were chosen. T. urticae was used as the test organisms. Three different suspensions (1x106, 1x107 and 1x108 conidia ml-1) were prepared in Tween 80. 2ml suspension of a single dose was sprayed onto down sides of bean leaf discs using hand sprayer. Mortality rates of T. urticae, in terms of LT50 values, were recorded daily for 5 days. Enzyme activities were investigated by petri plate assays and clear zones formed around the colonies indicated enzymatic activities. All tested fungal isolates were pathogenic to the T. urticae causing mortality between 64.2±5.6% and 100% on the 5th day after the application. LT50 values varied between 3.16±0.2 and 3.72±0.5 days. Mortality caused by PaF04 isolate was found to be significantly different (p lt;0.05). In conclusion, PaF isolates of B. bassiana have been determined to have potential to suppress T. urticae, in addition to their potential in control of Coleoptera, Lepidoptera, and Hymenoptera. The present results showed that the isolates used, especially PaF04, have a broad host range.
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