Clonostachys rosea: production by submerged culture and bioactivity against Sclerotinia sclerotiorum and Bemisia tabaci.

• Autor(a) principal: MASCARIN, G. M.
• Data de Publicação: 2022
• Outros Autores: SILVA, A. V. R. da, SILVA, T. P. da, KOBORI, N. N., MORANDI, M. A. B., BETTIOL, W.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da EMBRAPA (Repository Open Access to Scientific Information from EMBRAPA - Alice)
• Texto Completo: http://www.alice.cnptia.embrapa.br/alice/handle/doc/1148058; https://doi.org/10.3389/fmicb.2022.851000
• topic: Doença de Planta; Sclerotinia Sclerotiorum; Bemisia Tabaci; Mofo Branco; Controle Biológico; Fungo Para Controle Biológico; Biological control agents; Sclerotinia; Clonostachys rosea; Submerged fermentation; Solid state fermentation

Abstract: Among the prospective biocontrol agents, the saprophytic filamentous fungus Clonostachys rosea is an excellent necrotrophic mycoparasite of numerous plant pathogenic fungi. However, its commercial development has been hampered by mass production difficulties during solid-state fermentation. Conversely, the submerged liquid fermentation shortens the cultivation time while increasing yields of fungal propagules. However, this method has been overlooked for C. rosea. In this work, we investigated the impact of liquid pre-culture inoculum on the spore production by the two-stage fermentation process using rice grains in comparison to the traditional solid-state fermentation. In parallel, we studied the submerged cultivation of C. rosea by manipulating carbon-to-nitrogen (C:N) ratio and nitrogen source, with the further optimization of spore production in a benchtop bioreactor. Additional bioassays included assessing the bioactivity of water-dispersible microgranules (that contained a submerged conidia) against the whitefly (Bemisia tabaci biotype B) and Sclerotinia sclerotiorum (causal agent of the white mold). Our results showed a maximum concentration of 1.1 × 10⁹ conidia/g-dry-matter after 7 days of cultivation by two-stage fermentation process. The liquid fermentation yielded 1.4 × 10⁹ submerged conidia/ml after 7 days using a medium with a 50:1 C:N ratio, and it also induced the production of microsclerotia (MS) up to 1.35 × 10⁴/ml within 6 days with 10:1 C:N ratio; both media were supplemented with dextrose monohydrate and soybean meal. The fermentation batches carried out in a benchtop bioreactor with medium 50:1 C:N ratio and amended with soybean meal rendered a production peak on the fourth day, corresponding to 1.11 × 10⁹ conidia/ml and 4.35 × 10⁸ colony forming units (CFU)/ml. Following air-drying, the conidia production from air-dried microgranules of C. rosea biomass was estimated at 3.4 × 10¹⁰ conidia/g of formulated product upon re-hydration for 7 days. Both submerged conidia and MS of C. rosea inhibited 100% germination of S. sclerotiorum sclerotia by direct parasitism. The air-dried submerged conidia exhibited a suppressive activity on sclerotia (88% mycoparasitism) and early whitefly nymphs (76.2% mortality) that rendered LC₅₀ values of 3.2 × 10⁴ CFU/g soil and 1.5 × 10⁷ CFU/ml, respectively. Therefore, the submerged liquid culture of C. rosea may offer a feasible and cost-effective method for its large-scale production, alleviating critical constraints to their commercial use while providing an additional tool for management of B. tabaci and S. sclerotiorum.