Patterns of Occurrence and Activity of Entomopathogenic Fungi in the Algarve (Portugal) Using Different Isolation Methods

Abstract

Entomopathogenic fungi (EPF) are distributed in natural and agricultural soils worldwide. To investigate EPF occurrence in different botanical habitats and soil-ecoregions, we surveyed 50 georeferenced localities in the spring of 2016 across the Algarve region (South Portugal). Additionally, we compared three EPF isolation methods: insect baiting in untreated or pre-dried-soil and soil dilution plating on a selective medium. We hypothesized that forest habitats (oak and pine semi-natural areas) and the acidic soil ecoregion may favor EPF occurrence. Overall, EPF species were present in 68% of sites, widely distributed throughout the Algarve. The use of selective media resulted in higher recovery of EPF than did either soil-baiting method. Contrary to our hypothesis, neither vegetation type nor ecoregion appeared to influence EPF occurrence. Traditional and molecular methods confirmed the presence of five EPF species. Beauveria bassiana (34% of sites), was the most frequently detected EPF, using pre-dried soil baiting and soil dilution methods. However, baiting untreated soil recovered Fusarium solani more frequently (26% of sites), demonstrating the utility of using multiple isolation methods. We also found Fusarium oxysporum, Purpureocillium lilacinum and Metarhizium anisopliae in 14%, 8% and 2% of the sites, respectively. Three abiotic variables (pH, soil organic matter and Mg) explained 96% of the variability of the entomopathogen community (EPF and entomopathogenic nematodes) in a canonical correspondence analysis, confirming the congruence of the soil properties that drive the assemblage of both entomopathogens. This study expands the knowledge of EPF distribution in natural and cultivated Mediterranean habitats.

Biocontrol of Melolontha spp. Grubs in Organic Strawberry Plantations by Entomopathogenic Fungi as Affected by Environmental and Metabolic Factors and the Interaction with Soil Microbial Biodiversity

“…According to the microbiological evaluation of the soil population of the two fungal species, B. bassiana could be considered a common native species in the studied locations, while B. brongniartii was never found in the untreated soil samples. This result is in line with other reports showing that B. bassiana was a dominant entomopathogenic fungal species under different soil conditions [ 66 , 67 , 68 , 69 , 70 , 71 ]. However, its detection, as well as for other entomopathogenic fungi, can be affected by the method used for the analysis [ 70 ].…”

“…This result is in line with other reports showing that B. bassiana was a dominant entomopathogenic fungal species under different soil conditions [ 66 , 67 , 68 , 69 , 70 , 71 ]. However, its detection, as well as for other entomopathogenic fungi, can be affected by the method used for the analysis [ 70 ]. Considering that B. bassiana is the most widely distributed species of the whole Beauveria genus, with a wide range of parasitized species and capable of living as an endosymbiont of several plants species, its survival capacity and adaptation plasticity is not surprising [ 54 , 58 ].…”

Abundance of Entomopathogenic Fungi in Leaf Litter and Soil Layers in Forested Habitats in Poland

“…The dominance of B. bassiana in soils collected from various types of forests is also confirmed by studies conducted in Denmark [37], Finland [7], Poland [27,35,38,39], Japan [40], Italy [41,42] Spain [43,44], Austria [45], Mexico [46], Brasil [47] and Portugal [48]. Niemczyk et al [21], examining the occurrence of Beauveria spp.…”

“…Popowska-Nowak et al [ 25 ], who conducted research in various regions of Poland, showed that M. anisopliae and I. fumosorosea ( Cordyceps fumosorosea ) were the most frequently isolated species of entomopathogenic fungi from the soils of several-year-old forest nurseries, especially in the springtime, which, according to the authors, was associated with the higher humidity of the soil environment. Different research results by other authors may result from the fact that the species composition and the intensity of the occurrence of EPF in the soil are influenced by many factors, such as the content of organic matter, pH, soil type and method of its cultivation [ 7 , 8 , 9 , 21 , 47 , 48 , 68 , 69 ], as well as microclimatic conditions (temperature, humidity) and potential host density [ 36 , 68 ]. It could also be related to the methods of quantifying EPF abundance.…”

“…Two methods are generally used to detect EPF in soil: (1) Bait methods use Galleria mellonella L. (Lepidoptera: Pyralidae) or other insects [ 46 , 70 ] and are relatively simple and sensitive but provide rather semiquantitative data [ 71 , 72 , 73 ]; (2) plating methods using various selective media [ 22 , 40 , 74 , 75 , 76 ] that are particularly useful when quantification is necessary or when the input material is not soil (e.g., air and some plant parts). Bueno-Pallero et al [ 48 ] observed different patterns of EPF occurrence by using different isolation methods, particularly between insect baits and selective medium methodology. The use of selective media resulted in higher recoveries of EPF than either soil-baiting method.…”