Abstract

SARTI, Gabriela C.  and  MIYAZAKI, Silvia S.. Bacillus subtilis crude extracts with antifungal activity against soybean (Glycine max) phytopathogens and Bradyrhizobium japonicum coinoculation effect. Agrociencia [online]. 2013, vol.47, n.4, pp.373-383. ISSN 2521-9766.

Fungal species Fusarium solani and Pythium sp. are among the microorganisms causing diseases in pre and post harvest crop soybean (Glycine max). Four strains of the genus Bacillus (B. subtilis ATCC6633, B. amylolyticus, B. subtilis var. natto, B. subtilis var. natto domesticated) were tested to evaluate the inhibitory response of them on the phytopathogenic fungi previously mentioned. The inoculation treatments were 1) seeds inoculated with Bradyrhizobium japonicum, and 2) seeds coinoculated with B. japonicum and B. subtilis. Plants were grown in a thermostated culture chamber at 30±1 °C, 60 % relative humidity and 16/8 light-dark photoperiod for 35 d. Data were analyzed by ANOVA and means were compared by applying the Tukey test (p≤0.05). The in vitro assays of the strain B. subtilis ATCC6633 reduced the mycelial growth of Fusarium solani (50 %) and Pythium sp. (47 %) compared to controls. The coinoculation of B. japonicum and B. subtilis stimulated the growth of the whole plant by 125 %, 100 % aerial part, 235 % root, 20 % number of leaves, and 88 % nodule number compared to control. The strain B. subtilis ATCC6633 synthesized metabolites of proteinaceous nature and others with biosurfactant capacity. When the bacteria were grown in minimal saline medium, glycerol 1 % and concentrations of L-glutamic acid between 40 and 55 mM, the highest concentration of proteinaceous metabolites (35 µg protein mL^-1) was obtained and increased biofilm formation. Biofilm formation, the presence of biosurfactants and the release of antifungal metabolites positioned this bacterium in a situation competitively advantageous compared to the rest of the microbiota of the rhizosphere in the soybean plant.

Keywords : Bacillus subtilis; Fusarium solani; Pythium; Glycine max.; antifungal; coinoculation.

        · abstract in Spanish     · text in Spanish     · Spanish ( pdf )