Impact of Strains of Entomopathogenic Fungi On Some Main Groups of Soil Microorganisms

Abstract

The influence of entomopathogenic fungal strains -one Metarhizium anisopliae (Metsch.) Sorok. and seven Beauveria bassiana (Bals.-Criv.) Vuill. on some main groups of soil microorganisms was studied after introduction of their conidia into the soil. The soil samples were analyzed for densities of bacteria, actinomycetes and fungi by decimal dilutions of soil suspensions grown on selective media.The presence of conidia of fungal strains in the soil after a month from introduction was proved by bait method. Three of the strains of B. bassiana were established to be of the highest persistence, this being expressed by mortality of Galleria mellonella L. (Lepidoptera, Pyralidae) larvae from 70% to 90%, followed by strains 224Re of B. bassiana and 31 of M. anisopliae.The obtained results showed that examined strains of the entomopathogenic fungi manifested different in manner and varying in degrees of impact on density of the main groups of soil microorganisms. Relatively insignificant changes were established under the influence of the strains 224Re B. bassiana and 31 M. anisopliae. The other strains of B. bassiana caused alterations in microbial balance expressed in different manner -stimulation or suppression on density of free-living nitrogen-fixing microorganisms, mineral nitrogen utilizing bacteria, spore-forming bacteria, cellulose degrading microorganisms, actinomycetes, soil fungi. So each strain could be characterized by specific impact on examined groups of soil microorganisms.The strain 412 of B. bassiana showed the most strongly manifested stimulation effect on the heterotrophic microorganisms, on the mineral nitrogen utilizing bacteria, on the free-living nitrogen-fixing microorganisms and the soil fungi -14, 15, 7 and 30 times higher density of the microorganisms compared to the control treatments. The same strain caused high degree of suppression on densities of cellulose degrading microorganisms -0.0064 x 10 6 compared to 0.0305 x 10 6 CFU/g in the control treatment. Densities of the soil spore-forming bacteria were not affected by the examined strains of B. bassiana and M. anisopliae. In the conducted experiments it has been established that the manifested impact on actinomycetes density by strains of the entomopathogenic fungi B. bassiana and M. anisopliae was different in manner and varying in degrees, on the contrary to the stimulation influence on density of the soil fungi.

<b>Population density of <i>Beauveria bassiana</i> in soil under the action of fungicides and native microbial populations

“…Results obtained by Draganova, Donkova, and Georgieva (2008) showed that lineage 412 of B. bassiana stimulated the growth of soil fungi 30-fold above the control value. Because these microorganisms are heterotrophic, there may be a synergistic interaction between these populations (Draganova et al, 2008).…”

“…Results obtained by Draganova, Donkova, and Georgieva (2008) showed that lineage 412 of B. bassiana stimulated the growth of soil fungi 30-fold above the control value. Because these microorganisms are heterotrophic, there may be a synergistic interaction between these populations (Draganova et al, 2008). This interaction is important for the degradation of organic soil composts because degradation takes place in stages and includes the action of many physiologically different microorganisms (Stamford, Rodrigues, Heck, & Andrade, 2005).…”

Evaluation of Native Entomopathogenic Fungi for the Control of Fall Armyworm (Spodoptera frugiperda) in Thailand: A Sustainable Way for Eco-Friendly Agriculture

“…Interestingly, of all the entomopathogens, only fungi do not require ingestion or the openings like nematodes to gain entry into their host, but instead use enzymes to penetrate through the cuticle [11]. Among the identified species of fungi, the most utilized are in the genera Beauveria, Cordyceps, Isaria, Lecanicillium, Metarhizium, and Nomuraea, among others, of which several bio-insecticides are attributed [12][13][14]. Due to their ubiquitous nature and ability to survive in different kinds of environments, these entomopathogenic fungi have been tried against insects in several parts of the world and have emerged victorious in many aspects [12,15,16].…”

Interactions between the entomopathogenic fungus Beauveria bassiana and the Neotropical predator Eriopis connexa (Coleoptera: Coccinellidae): Implications in biological control of pest

“…Vuill., L. longisporum and Isaria fumosorosea Wize, have been successfully utilized as biological control agents against numerous pests including aphids (de Faria and Wraight 2007;Powell and Pell 2007;Draganova et al 2008). The main biological attributes for a mycoinsecticide are the virulence toward the target insect and that it is not harmful to other beneficial organisms such as parasitoids and predators (Riddick et al 2009).…”