|MASCARIN, GABRIEL - Embrapa|
|KOBORI, NILCE - Embrapa|
|VITAL, RAYON - Embrapa|
|QUINTELA, ELIANA - Embrapa|
Submitted to: World Journal of Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2013
Publication Date: 1/15/2014
Publication URL: http://handle.nal.usda.gov/10113/60576
Citation: Mascarin, G.M., Kobori, N.N., Vital, R.C., Jackson, M.A., Quintela, E.D. 2014. Production of microsclerotia by Brazilian strains of Metarhizium spp. using submerged liquid culture fermentation. World Journal of Microbiology and Biotechnology. 30(5):1583-1590.
Interpretive Summary: Various species of the fungus Metarhizium are undergoing evaluation for use as a biological control agent for various insect pests in Brazil. In this study, we evaluated their potential to produce a resistant fungal form termed a “microsclerotium”. These microsclerotia have been shown to be an excellent form of the Metarhizium for use in granular formulations for control of soil-dwelling insects. Our studies showed that all the Brazilian Metarhizium isolates tested produced high concentrations of microsclerotia using liquid fermentation. The microsclerotia produced by these Brazilian isolates survived drying and had good shelf-life when stored at either -20 °C or 26 °C. These Brazilian isolates of Metarhizium can be grown using liquid fermentation to produce high concentrations of stable microsclerotia for use in controlling soil-dwelling insect pests.
Technical Abstract: We investigated the potential production and desiccation tolerance of microsclerotia (MS) by Brazilian strains of Metarhizium. anisopliae [Ma], M. acridum [Mc] and M. robertsii [Mr]. These fungi were grown in a liquid medium containing 16 g carbon l-1 with a carbon:nitrogen ratio of 50:1. One hundred ml cultures were grown in 250 ml Erlenmeyer flasks in a rotary incubator shaker at 28 °C and 200 rpm for 5 days. Five day-old MS were harvested, mixed with diatomaceous earth (DE) and air-dried for 2 days at 30 °C. The air-dried MS-DE granular preparations were milled by mortar+pestle and stored in centrifuged tubes at either 26 or –20 °C. Desiccation tolerance and conidia production were assessed for dried MS granules by measuring hyphal germination after incubation for 2 days on water agar plates at 26 °C and for conidia production following 7 days incubation. Yields of MS by all strains of Metarhizium were 6.1–7.3 × 106 l-1 after 3 days growth with maximum MS yields (0.7–1.1 × 107 l-1) after 5 days growth. No differences in biomass accumulation were observed after 3 days growth, whereas Ma-CG168 showed the highest biomass accumulation after 5 days growth. Dried MS-DE preparations of all fungal strains were equally tolerant to desiccation (= 93% germination) and highest conidia production was obtained by MS granules of Mc-CG423 (4 × 10**9 conidia g-1). All MS granules showed similar stability after storage at either at 26 or –20 °C for 3.5 months.