Coating of bean seeds with alginate-F4A and its effect against Fusarium oxysporum f. sp. phaseoli

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Rich in proteins, vitamins, and minerals, beans (Phaseolus vulgaris) contribute to food security and are also an income source for family farmers in all regions of Brazil. One of the main challenges in managing the bean crop is the control of the fungus Fusarium oxysporum f. sp. phaseoli, etiologic agent of fusarium wilt disease. The fungus can reduce grain yield by up to 70%, depending on the severity of the disease. Seeds from affected soils can carry spores that germinate when environmental conditions become favorable for the fungus. Aiming to reduce the insertion of this fungus in crops, our research group studied the coating of bean seeds with the antifungal compound F4A, a semi-purified extract from cultures of the LV strain of Pseudomonas aeruginosa. F4A is obtained by chromatographic methods and consists of four molecules: phenazine-1-carboxylic acid, phenazine-1-carboxamide, indolin-3-one, and fluopsin C. The seed coating method was established using the ionic gelling technique by incorporation of F4A in a sodium alginate solution (1.5% w/v), at 100 µg/mL (F4A/ALG). Bean seeds of cultivar BRS-style were immersed in F4A/ALG solution and then individually placed in calcium chloride solution (2% w/v). The coated seeds were dried at 30 °C for 2 hours, resulting in the formation of a thin film around the grains. The treatment effect was evaluated for antifungal activity and germination rate, both evaluated simultaneously in Petri dishes (150 mm) with paper for seed germination. Therefore, 9 treated seeds were immersed in a suspension of conidia (106) and placed on paper moistened with water. The same procedure was performed with seeds coated only with alginate (control group). After 4 days of incubation, it was possible to observe that 88.8% of the seeds coated with F4A/ALG germinated, while the control group had a germination rate of 33.3%. Regarding the antifungal effect, among the treated seeds, 66.6% did not show infection points, while 33.3% developed a moderate infection. In the control group, 88.8% of the seeds were intensely colonized, while 11.2% had a moderate infection. Based on the results, we believe that coating seeds with F4A/ALG can be an alternative to reduce the spread of fusarium wilt disease mediated by seeds.

  • 1 Departamento de Microbiologia / Centro de Ciências Biológicas / Universidade Estadual de Londrina
Eixo Temático
  • Inovação e Biotecnologia
Natural products
secondary metabolites