Isolation of Entomopathogenic and Opportunistic Fungi from Soil in Duhok Province,Kurdistan Region of Iraq by Different Selective Isolation Media

Abstract

Soil is a natural habitat for several important insect pathogenic fungi which play a key role in regulating populations of soil dwelling insect pests. Forty soil samples were collected during 2012-2013 from different agro ecosystems at Duhok governorate were screened for the presence of soil dwelling entomopathogenic fungi using four different selective isolation media. The four isolation media were prepared by modifying previously prepared DOC2 medium and a selective medium based on the use of Cetyletrimethyl ammonium bromide (CTAB) with oatmeal agar (OT) as a basal medium. The percentage occurrence of fungi and number of detected species was significantly affected by the type of isolation medium. The least number of recovered species (5 species) was on DOC2 medium, whereas, the highest number (14 species) was displayed by CTAB+OT medium. The two true entomopathogenic species Lecanicillium lecanii and Metarhizium anisopliae were successfully recovered only with our new formula by combination of DOC2+CTAB and OT+CTAB media, whereas, DOC2 and DOC2+OT media failed to recover the two species. This result indicated that addition of CTAB to media was a vital factor for the recovery of the two entomopathogenic species. L. lecanii and M. anisopliae have been recorded for the first time from Iraqi soil. Several other opportunistic pathogens were also detected. These include Aspergillus flavus, A.parasiticus, Clonostachys rosea and Fusarium species. The distribution of entomopathogenic and opportunistic fungi is discussed in relation to different agroecosystems and to some physical and chemical characteristics of soil samples.

Key words: Entomopathogenic fungi, soil, Iraq.