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Developing a strain improvement system for the entomopathogenic fungus Beauveria basssiana: a way to get better biocontrol agents?
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Reyes Haro, Laura Estefanía (2018) Developing a strain improvement system for the entomopathogenic fungus Beauveria basssiana: a way to get better biocontrol agents? PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3449684~S1
Abstract
Biocontrol agents (BCAs) based on entomopathogenic fungi (EPF) are playing an increasing role in Integrated Pest Management programmes. At present, the commercially available EPF consist of wild type strains isolated from nature, however, there is potential to breed more effective strains by recombining wild types with complementary characteristics. EPF Beauveria bassiana represents one of the most important organisms used to kill arthropod pests, as they occurred naturally in the environment, do not leave residual activity, are safer for human manipulation and they usually show a high virulence. The aim of this research was to develop a system to improve strains of the entomopathogenic fungus B. bassiana through genetic recombination. A group of 50 Beauveria strains were genotyped using multi-locus sequencing and mating gene analysis, and then phenotyped with respect to their virulence against Diamondback moth (DBM), thermal biology, tolerance of UV light, and conidial production. A phylogenetic analysis identified two different Beauveria species within the fungal collection: B. bassiana (78%) and Beauveria pseudobassiana (16%). Seven strains from different places of origin were selected with phenotypes such as tolerance to UV-B radiance, thermotolerance, virulence and potentially compatible mating types for parasexual recombination studies. Spontaneously generated nitrate non-utilizing (nit) mutants were produced from these strains using a potassium chlorate-amended selective medium and 35 vegetative compatibility groups were determined within the 50 isolates of Beauveria spp. Recombination by hyphal fusion and protoplast fusion proved to be feasible and was observed in two out of three crosses. Only one cross (X2) showed higher radial growth than the parental strains between 20 and 30 °C. Nine fungal strains were selected to investigate the potential for inducing sexual recombination by pairing complementary mating types on three different media that have probed work well in other fungal species (oatmeal agar, malt extract agar, and Czapek Dox agar +/- biotin). After six months, both in vitro and in vivo assays led to the generation of structures resembling synnemata, however no fruiting bodies nor other clear sexual structures were observed. No relationship was found between the geographical origin of the strains and their tolerance to temperature or UV-B light, suggesting that micro-environmental conditions can play a more important role in the development of determined traits of organisms sourced from specific ecosystems than the latitude or altitude of sampling locations. This study provides a significant amount of information describing several methodologies for parasexual and sexual recombination of this fungus, expanding the current knowledge of this valuable EPF.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QL Zoology S Agriculture > SB Plant culture |
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Library of Congress Subject Headings (LCSH): | Biological pest control agents, Entomopathogenic fungi , Diamondback moth -- Biological control | ||||
Official Date: | November 2018 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Chandler, David | ||||
Sponsors: | Ecuador. Secretaría de Educación Superior, Ciencia, Tecnología e Innovación | ||||
Format of File: | |||||
Extent: | xiii, 198 leaves : illustrations, charts | ||||
Language: | eng |
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