Show simple item record

GENETIC DIVERSIFICATION, SAPROPHYTIC COMPETENCE AND GENETIC ENHANCEMENT OF THE ENTOMOPATHOGENIC FUNGUS METARHIZIUM

dc.contributor.advisorSt. Leger, Raymond Jen_US
dc.contributor.authorPava-Ripoll, Monica Patriciaen_US
dc.date.accessioned2010-02-19T06:46:21Z
dc.date.available2010-02-19T06:46:21Z
dc.date.issued2009en_US
dc.identifier.urihttp://hdl.handle.net/1903/9881
dc.description.abstractEntomopathogenic fungi are being investigated as alternatives to chemical insecticides. This study explored the versatility of the entomopathogenic fungus Metarhizium anisopliae by examining its diversification, saprophytic competence and potential for genetic enhancement. M. anisopliae is a radiating species containing both generalist and specialized lineages with broad and narrow host ranges and as such provides an excellent model system to study the evolution of pathogenesis. Using 18S RNA and protease sequences, I demonstrated that strains can be selected representing evolutionary distances ranging from <1 to 8 MY and their natural molecular variation allows analysis of processes of adaptive change. M. anisopliae is particularly abundant in the rhizosphere. Germination of M. anisopliae strain 2575 was >96% in 1 mg/ml root exudate (RE) and growth in RE resulted in 29 (58%) genes being up-regulated and 21 (42%) down-regulated. The identity of these genes is helping to define the physiological requirements for rhizosphere competence. Hypothetical and orphans proteins (41.4%) were also actively expressed indicating that many previously uncharacterized genes may have functions related to survival at the soil-root interphase. Using the fungus as a delivery vehicle for foreign toxins presents a powerful approach for increasing virulence. M. anisopliae was modified to express a scorpion toxin (AaIT) in insect haemolymph and bioassayed against the coffee berry borer Hypothenemus hampei. AaIT increased mortality up to 56.6%, and reduced the medial lethal concentration (LC <sub>50 </sub>) by 15.7-fold and the average survival time (AST) by 20.1%. The AaIT gene and the M. anisopliae esterase gene (Mest1) were inserted into three strains of Beauveria bassiana (ARSEF 252, 8998 and 9184) with high, medium and low mortality, respectively, against the Colorado potato beetle (CPB) Leptinotarsa decemlineata. Mortality rates were strain- and dose- dependant and increased from 16.1 to 36.7% in single transformants (AaIT or Mest1) and from 7.1 to 33.5% in double transformants (AaIT-Mest1). The AST was reduced up to 33% and the LC<sub>50 </sub> up to 5.9-fold. Although singly both AaIT and Mest1 increased the killing power of B. bassiana against second instar CPB, combining AaIT and Mest1 together did not produce synergistic effects.en_US
dc.titleGENETIC DIVERSIFICATION, SAPROPHYTIC COMPETENCE AND GENETIC ENHANCEMENT OF THE ENTOMOPATHOGENIC FUNGUS METARHIZIUMen_US
dc.typeDissertationen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.contributor.departmentEntomologyen_US
dc.subject.pqcontrolledBiology, Entomologyen_US
dc.subject.pqcontrolledBiology, Molecularen_US
dc.subject.pqcontrolledBiology, Geneticsen_US
dc.subject.pquncontrolledBeauveria bassianaen_US
dc.subject.pquncontrolledHypothenemus hampeien_US
dc.subject.pquncontrolledLeptinotarsa decemlineataen_US
dc.subject.pquncontrolledBiological controlen_US
dc.subject.pquncontrolledEntomopathogenic fungal transformationen_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record