Survey of entomopathogenic and mycoparasitic fungi in the soil of onion and garlic fields in the Czech Republic and Israel

Bulb crops are attacked by various soil-dwelling pests and pathogens. Entomopathogenic (EPFs) and mycoparasitic fungi (MPFs) which are distributed in natural and agricultural soils worldwide can play an important role as natural enemies of bulb pests. The species richness and density of these fungi in onion and garlic fields have not been investigated. The aim of this study was to determine the occurrence of EPFs and MPFs in soils where these crops were grown and compared the data from sites of the Czech Republic and Israel. Methods of fungi isolation and quantification were based on elution of soil samples by water and cultivation using selective media with dodine for EPFs and cultivation using potato dextrose agar with chloramphenicol for MPFs. Entomopathogenic fungi Beauveria spp., Isaria spp., Lecanicillium spp., Metarhizium spp., Purpureocillium spp. and mycoparasitic fungi Trichoderma spp. were isolated from soil samples in both countries. The highest density was observed in the genus Metarhizium in both countries. Metarhizium spp. were most abundant in the site Mlýn Podhora in the Czech Republic. The average density of colony-forming units (CFU) per 1 mL of soil sample was 1.47 × 104. The lowest density was observed in the genus Beauveria in both countries, up to 5.93 × 102 CFU per 1 mL of soil sample. Soils in the Czech Republic contained about ten times higher number of EPFs compared to Israel. Rather higher prevalence of MPFs was also found in the Czech Republic. Possible reasons for within and between countries variability in EPFs and MPFs occurrence are discussed.