Fungus was efficient against two banana diseases

The fungus Beauveria caledonica has simultaneous action against banana fusariosis – Panama disease and its strains have potential for managing the “borer” or “banana urchin” (Cosmopolites sordidus), two of the main phytosanitary problems of the crop. Still little studied in Brazil and around the world, it was recently isolated by scientists from Embrapa, Unicamp and Bioversity International, Colombia, to control pests, especially beetles. Embrapa Environment analyst Gabriel Mascarin highlights that this is the first study that demonstrates this capacity of the fungus, found in the commercial banana production region in Registro, SP.

"In our research, we isolated banana borer adults collected in the field and then made an emulsifiable oil formulation to increase its effectiveness, accelerating the infection process and controlling the pest", explains Mascarin. "Furthermore, comparatively, isolates of B. caledonica were more efficient in controlling borer adults, which emphasizes their potential for biocontrol of this insect.” We also discovered that this fungus produces a secondary compound called oosporin, which had an antagonistic action on fusarium. This effect is unprecedented", explains Mascarin.

Oosporin was detected and quantified by the team led by professor Ljubica Tasic from the Unicamp Chemistry Institute. “In an in vitro test against fusarium, we found that the filtrates extracted from the fermented broth of B. caledonica containing the compound oosporin, exhibited antifungal activity, resulting in a strong inhibition of the germination of the phytopathogen”, adds Mascarin. "This result expands our knowledge about the spectrum of biological activity of B. caledonica. It also provides new insights into its lifestyle, highlighted by its remarkable antifungal role against this destructive banana pathogen," says the analyst.

Main banana diseases

The borer and fusariosis are among the most important banana pests and diseases, respectively. The insect has a direct effect on the rhizome, weakening the plant's root system, reducing nutrient absorption and causing significant productivity losses. Adults may also play a role in spreading and exacerbating infections by soil-borne plant pathogens.

Banana fusariosis also causes severe yield losses in bananas and the pathogen spreads rapidly through various means. A combination of management practices in commercial plantations is necessary to mitigate the increase in borer populations and the incidence of the fungus. However, controlling these organisms still presents a major challenge to producers and it is very important to search for biological control alternatives to complement field management.

Soil is an important reservoir of entomopathogenic fungi, being a place in which insect pathogens can infect their hosts and multiply, persist and grow. Therefore, understanding the interaction between C. sordidus, which causes banana blight, and entomopathogenic fungi, in addition to understanding how both may be related to other microorganisms in the soil, is crucial for the development of fungal-based biopesticides.

It has been demonstrated that certain commercial banana plantations, infested by the banana borer, can harbor a very specialized community of entomopathogenic fungal species. It is interesting to note that all three strains of B. caledonica naturally isolated from C. sordidus were able to produce and secrete the red pigment known as oosporin in both agar-based and liquid media, although no signs of this pigment were observed for other strains of Beauveria bassiana – a fungus that has a broad spectrum of action on insect pests, including several species of agricultural importance. This secondary metabolite may be associated with the fungus' greater virulence against the banana borer, although this needs to be further investigated.

"To accelerate the rate and increase the level of banana borer mortality from our best isolate of B. caledonica, we formulated conidia of this fungus with an emulsifiable, fully biodegradable vegetable oil, showing that the oil likely plays an important role in adhesion of the fungus to the insect's body and facilitates its infection", explains Embrapa Meio Ambiente researcher Jeanne Prado.

According to Embrapa Genetic Resources and Biotechnology researcher Rogerio Biaggioni Lopes, the development of biopesticides with more virulent strains to the target insect, whether through laboratory selection, formulation, new application strategies or genetic manipulation, can make this microorganism more competitive. for use in banana borer management programs, thus contributing to more balanced cultivation systems. “As far as we know,” says Mascarin, “there are no commercial products with this microorganism. We are ahead of the curve here in Brazil and we still have a lot of ground to cover in the search for an effective biological product to simultaneously control pests and diseases in bananas.”

The work of Gabriel Mascarin, Jeanne Prado and Márcia Assalin, from Embrapa Meio Ambiente, Lucas Gelin Martins, Erik Sobrinho Braga and Ljubica Tasic, from Unicamp, Miguel Dita, from Bioversity International, Cali, Colombia and Rogerio Lopes, from Embrapa Genetic Resources and Biotechnology, was published in Pest Management Science, can be accessed here It was financed by the São Paulo State Research Support Foundation (Fapesp).