Beauveria bassiana and Metarhizium anisopliae endophytically colonize cassava roots following soil drench inoculation

AbstractWe investigated the fungal entomopathogens Beauveria bassiana and Metarhizium anisopliae to determine if endophytic colonization could be achieved in cassava. An inoculation method based on drenching the soil around cassava stem cuttings using conidial suspensions resulted in endophytic colonization of cassava roots by both entomopathogens, though neither was found in the leaves or stems of the treated cassava plants. Both fungal entomopathogens were detected more often in the proximal end of the root than in the distal end. Colonization levels of B. bassiana were higher when plants were sampled at 7–9days post-inoculation (84%) compared to 47–49days post-inoculation (40%). In contrast, the colonization levels of M. anisopliae remained constant from 7–9days post-inoculation (80%) to 47–49days post-inoculation (80%), which suggests M. anisopliae is better able to persist in the soil, or as an endophyte in cassava roots over time. Differences in colonization success and plant growth were found among the fungal entomopathogen treatments

Fungal diversity associated to the olive moth, prays oleae Bernard : a survey for potential entomopathogenic fungi

Olive production is one of the main agricultural activities in Portugal. In the region of Trás-os-Montes this crop has been considerably affected by Prays oleae. In order to evaluate the diversity of fungi on P. oleae population of Trás-os-Montes olive orchards, larvae and pupae of the three annual generations (phyllophagous, antophagous and carpophagous) were collected and evaluated for fungal growth on their surface. From the 3828 larvae and pupae, a high percentage of individuals exhibited growth of a fungal agent (40.6%), particularly those from the phyllophagous generation. From all the moth generations, a total of 43 species from 24 genera were identified, but the diversity and abundance of fungal species differed between the three generations. Higher diversity was found in the carpophagous generation, followed by the antophagous and phyllophagous generations. The presence of fungi displaying entomopathogenic features was highest in the phyllophagous larvae and pupae, being B. bassiana the most abundant taxa. The first report of B. bassiana presence on P. oleae could open new strategies for the biocontrol of this major pest in olive groves, since the use of an already adapted species increases the guarantee of success of a biocontrol approach. The identification of antagonistic fungi able to control agents that cause major olive diseases, such as Verticillium dahliae, will benefit future biological control approaches for limiting this increasingly spreading pathogen.This work was supported by Science and Technology Foundation (Fundação para a Ciência e Tecnologia – FCT) project PTDC/AGR-AAM/102600/2008 “Entomopathogenic fungi associated to olive pests: isolation, characterization and selection for biological control”. The first author is grateful to the Science and Technology Foundation for the PhD grant SFRH/BD/44265/2008

Metarhizium anisopliae Pathogenesis of Mosquito Larvae: A Verdict of Accidental Death

Metarhizium anisopliae, a fungal pathogen of terrestrial arthropods, kills the aquatic larvae of Aedes aegypti, the vector of dengue and yellow fever. The fungus kills without adhering to the host cuticle. Ingested conidia also fail to germinate and are expelled in fecal pellets. This study investigates the mechanism by which this fungus adapted to terrestrial hosts kills aquatic mosquito larvae. Genes associated with the M. anisopliae early pathogenic response (proteinases Pr1 and Pr2, and adhesins, Mad1 and Mad2) are upregulated in the presence of larvae, but the established infection process observed in terrestrial hosts does not progress and insecticidal destruxins were not detected. Protease inhibitors reduce larval mortality indicating the importance of proteases in the host interaction. The Ae. aegypti immune response to M. anisopliae appears limited, whilst the oxidative stress response gene encoding for thiol peroxidase is upregulated. Cecropin and Hsp70 genes are downregulated as larval death occurs, and insect mortality appears to be linked to autolysis through caspase activity regulated by Hsp70 and inhibited, in infected larvae, by protease inhibitors. Evidence is presented that a traditional host-pathogen response does not occur as the species have not evolved to interact. M. anisopliae retains pre-formed pathogenic determinants which mediate host mortality, but unlike true aquatic fungal pathogens, does not recognise and colonise the larval host

Infection of the malaria mosquito, Anopheles gambiae, with two species of entomopathogenic fungi: effects of concentration, co-formulation, exposure time and persistence

<p>Abstract</p> <p>Background</p> <p>Entomopathogenic fungi <it>Metarhizium anisopliae </it>and <it>Beauveria bassiana </it>isolates have been shown to infect and reduce the survival of mosquito vectors.</p> <p>Methods</p> <p>Here four different bioassays were conducted to study the effect of conidia concentration, co-formulation, exposure time and persistence of the isolates <it>M. anisopliae </it>ICIPE-30 and <it>B. bassiana </it>I93-925 on infection and survival rates of female <it>Anopheles gambiae sensu stricto</it>. Test concentrations and exposure times ranged between 1 × 10⁷- 4 × 10¹⁰conidia m^-2and 15 min - 6 h. In co-formulations, 2 × 10¹⁰conidia m^-2of both fungus isolates were mixed at ratios of 4:1, 2:1, 1:1,1:0, 0:1, 1:2 and 1:4. To determine persistence, mosquitoes were exposed to surfaces treated 1, 14 or 28 d previously, with conidia concentrations of 2 × 10⁹, 2 × 10¹⁰or 4 × 10¹⁰.</p> <p>Results</p> <p>Mosquito survival varied with conidia concentration; 2 × 10¹⁰conidia m^-2was the concentration above which no further reductions in survival were detectable for both isolates of fungus. The survival of mosquitoes exposed to single and co-formulated treatments was similar and no synergistic or additive effects were observed. Mosquitoes were infected within 30 min and longer exposure times did not result in a more rapid killing effect. Fifteen min exposure still achieved considerable mortality rates (100% mortality by 14 d) of mosquitoes, but at lower speed than with 30 min exposure (100% mortality by 9 d). Conidia remained infective up to 28 d post-application but higher concentrations did not increase persistence.</p> <p>Conclusion</p> <p>Both fungus isolates are effective and persistent at low concentrations and short exposure times.</p