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Microsclerotia from Metarhizium robertsii: Production, ultrastructural analysis, robustness, and insecticidal
Jennifer Lorena García Riaño1, Gloria Patricia Barrera2, Leonardo Castellanos Hernández3
1Corporación Colombiana de Investigación Agropecuaria - Agrosavia. Centro de Investigación Tibaitatá, Cundinamarca, Mosquera, 250047, Colombia; Universidad Nacional de Colombia, Sede Bogotá, Facultad de Ciencias, Departamento de Química, Carrera 30 # 45, Bogotá, D.C., 111321, Colombia.
Abstract:
Microsclerotia (MS) are considered one of the most promising propagules for use as active ingredients in biopesticides due to their tolerance to abiotic factors and ability to produce infective conidia for the control of pests. Therefore, the objective of this research was to establish the conditions required to induce the formation of microsclerotia in Metarhizium robertsii Mt004 and to study its development process, tolerance to abiotic factors and insecticidal activity of MS-derived conidia. M. robertsii started to form hyphal aggregates after 2 days and looked more compact after 8 days. MS were mature and pigmented after 20 days. The final yield was 2.0 × 103 MS/mL and MS size varied between 356.9 and 1348.4 μm. Ultrastructure analysis revealed that mature MS contained only a few live cells embedded in an extracellular matrix. Mature MS were more tolerance to UV-B radiation, heat and storage trials than conidia from Solid State Fermentation. MS-derived conidia were as virulent as conidia against Diatraea saccharalis larvae. These results showed that MS are promising propagules for the development of more persistent and efficient biopesticides for harsh environmental conditions. Our findings provide a baseline for production and a better understanding of microsclerotia development in M. robertsii strains.
Insights
Microsclerotia (MS) from Metarhizium robertsii show enhanced tolerance to environmental stress and produce virulent conidia. These findings support MS as promising ingredients for developing robust biopesticides.
Area of Science:
- Agricultural Science
- Mycology
- Biotechnology
Background:
- Microsclerotia (MS) are vital propagules for biopesticides, offering abiotic tolerance and infective conidia for pest control.
- Metarhizium robertsii is a fungus with potential for biopesticide development.
Purpose of the Study:
- To optimize conditions for Metarhizium robertsii microsclerotia (MS) formation.
- To investigate MS development, abiotic tolerance, and the insecticidal efficacy of MS-derived conidia.
Main Methods:
- Inducing MS formation in Metarhizium robertsii Mt004.
- Monitoring MS development, yield, and size.
- Assessing MS tolerance to UV-B, heat, and storage.
- Evaluating insecticidal activity against Diatraea saccharalis larvae.
Main Results:
- MS formation in M. robertsii Mt004 took 20 days, yielding 2.0 × 10^3 MS/mL.
- Mature MS exhibited greater tolerance to UV-B, heat, and storage compared to conidia.
- MS-derived conidia demonstrated virulence comparable to standard conidia against D. saccharalis.
Conclusions:
- Microsclerotia are robust propagules suitable for biopesticides in challenging environments.
- Optimized MS production and understanding their development enhance biopesticide persistence and efficacy.
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