Formation of microsclerotia in three species of Beauveria and storage stability of a prototype granular formulation

Beauveria bassiana is the only species from the Beauveria genus that has been previously described as forming microsclerotia [Wang, H.-H., Wang, J.-L., Li, Y.-P., Liu, X., Wen, J.-Z., & Lei, Z.-R. (2011). Liquid culturing of microsclerotia of Beauveria bassiana, an entomopathogenic fungus to con...

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Bibliographic Details
Published in:Biocontrol science and technology 2018-12, Vol.28 (12), p.1097-1113
Main Authors: Villamizar, Laura F., Nelson, Tracey L., Jones, Sandra A., Jackson, Trevor A., Hurst, Mark R. H., Marshall, Sean D. G.
Format: Article
Language:English
Subjects:
Air monitoring
Ambient temperature
Beauveria
Beauveria bassiana
biopesticide
Carbon
Carbon sources
Conidia
Controlled release
Diatomaceous earth
Entomology
Entomopathogenic fungi
entompathogenic fungus
Fermentation
Fungi
Germination
Granular materials
Insects
Microsclerotia
Nitrogen
Overwintering
Shelf life
Species
Storage
Storage stability
Storage temperature
Sustained release
Temperature effects
Viability
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Summary:Beauveria bassiana is the only species from the Beauveria genus that has been previously described as forming microsclerotia [Wang, H.-H., Wang, J.-L., Li, Y.-P., Liu, X., Wen, J.-Z., & Lei, Z.-R. (2011). Liquid culturing of microsclerotia of Beauveria bassiana, an entomopathogenic fungus to control western flower thrip, Frankliniella occidentalis in Journal of Applied Entomology, 48(3), 588-595]. Microsclerotia (MS) are compact, melanised aggregates that have been recognised in plant pathogenic fungi as overwintering structures. MS were successfully produced in shake flask cultures from three different Beauveria species (B. bassiana, B. brogniartii and B. pseudobassiana) using liquid media containing a low carbon to nitrogen ratio and replacing glucose with a complex carbon source. Maximum MS yield after 10 days fermentation was 8.46 × 10 3 MS/mL obtained with B. pseudobassiana AgR-F704, a New Zealand fungus isolated from the African black beetle (Heteronychus arator F.). Using this isolate, MS were produced using two C:N compositions, formulated with diatomaceous earth and air dried and monitored for germination and storage stability. Germination of MS granules varied with C:N ratio and storage temperature. MS produced using a higher carbon concentration maintained 100% germination after six months of storage at 4°C, but when stored at 20°C, the germination rate was reduced to 68%. In contrast, MS produced using a lower carbon concentration showed reduced germination (0 to 18%) after storage for more than two months at either temperature and had lost viability completely after six months. Conidia production from surviving MS was estimated at 10 9  conidia/g of granules. Results demonstrated that Beauveria species are able to form MS in submerged culture and those produced in the relatively higher carbon medium were capable of surviving under low moisture, ambient temperature storage and are able to produce conidia after germination; all of these attributes suggest that MS can be incorporated into granules as a new sustained release strategy to control soil-dwelling insects.
ISSN:0958-3157
1360-0478
DOI:10.1080/09583157.2018.1514584