Bacteria reduces Fusarium wilt in banana plants

Researchers have identified the GD7-29 strain of Streptomyces angustmyceticus as a candidate for biocontrol of Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense tropical race 4, known as Foc TR4. The bacterium inhibited 70,1% of the pathogen's mycelial growth in an in vitro assay. In an experiment with potted plants, it achieved 50,8% control efficiency (DOI 10.1016/j.pestbp.2026.107249).

The study points to the strain as a promising agent for sustainable disease management. Fusarium wilt of bananas limits global crop production. Foc TR4 causes leaf yellowing, vascular wilt, and plant death. Control is difficult due to the fungus's persistence in the soil and in infected tissues. The work also highlights the lack of effective chemical control and the limited availability of resistant cultivars.

The GD7-29 strain came from the rhizosphere of healthy banana plants of the Brazilian cultivar, from the Cavendish group, in Huizhou, Guangdong province, China. Researchers isolated 114 bacteria. Seven showed antagonistic activity against Foc TR4. GD7-29 exhibited the strongest antifungal effect.

Bacterial identification

The identification of the bacterium combined morphological observations, physiological and biochemical tests, and molecular analyses. The data placed the strain within Streptomyces angustmyceticus. According to the study, this constitutes the first report of the use of this species against Foc TR4.

In pot trials, plants inoculated only with Foc TR4 showed typical symptoms, such as yellowing of leaves and darkening of the corm. The incidence of the disease reached 93,3% in the control group with the pathogen. In the group treated with GD7-29, it dropped to 61,1%. The disease index decreased from 79,7 to 39,2.

Plant growth

The strain also promoted plant growth. Compared to the uninoculated control, the treatment increased fresh mass by 23,3%, plant height by 14,2%, corm diameter by 15,2%, and relative chlorophyll content by 6,5%. The bacteria solubilized potassium and inorganic phosphate. It also produced protease and siderophores. It did not exhibit lignin degradation capacity.

The supernatant from the GD7-29 culture also showed antifungal activity. At tested concentrations of 5%, 10%, and 20%, the supernatant reduced the mycelial growth of Foc TR4. At a concentration of 20%, the inhibition reached 70,8%. The supernatant also delayed and reduced the germination of conidia of the pathogen.

Metabolomics analysis

Metabolomic analysis identified 1.409 metabolites with differential abundance. Among these, researchers selected 48 compounds with antifungal, antibacterial, or growth-promoting activity, based on literature records. These compounds included antibiotics, flavonoids, polyketides, terpenoids, alkaloids, non-ribosomal peptides, and sulfonamides.

The GD7-29 genome presented a linear chromosome with 7.810.685 base pairs and a guanine and cytosine content of 72,43%. Annotation indicated 6.729 predicted coding regions. The analysis also identified 33 gene clusters of biosynthesis linked to secondary metabolites, including polyketides, terpenes, non-ribosomal peptides, and post-translationally modified peptides.

The volatile organic compounds produced by the strain also reduced the growth of Foc TR4. The assay indicated 67,3% inhibition. Gas chromatography-mass spectrometry analysis detected five characteristic volatiles. Butanoic acid showed the highest relative abundance, accounting for 63,05% of the total peak area.

Commercial compounds

In bioassays with commercial compounds, butanoic acid inhibited Foc TR4 in a concentration-dependent manner. Inhibition rates reached 13,9%, 35,8%, and 60,3% at concentrations of 0,1, 1, and 5 milliliters per liter. At a low concentration of 0,1 milliliter per liter, the compound increased the fresh mass, height, and corm diameter of banana plants. In a biocontrol assay, it reduced the disease index from 75,4 to 60,5, with an efficiency of 19,8%.

GD7-29 also activated genes related to banana plant defense. The study recorded an increase in the expression of markers of the salicylic acid, jasmonic acid, and ethylene pathways in the first days after inoculation. The researchers indicate a systemic resistance-inducing effect associated with the treatment.

The results still depend on validation outside of controlled conditions. The study recommends field trials in different locations and growing seasons, evaluating application timing, colonization, productivity, soil health, and economic return compared to chemical controls.