Development of seed and leaf inoculants of the biocontrol agent Bacillus amyloliquefaciens.

SYDORENKO, OKSANA; CORREA OLGA S,; PUCHEU NORMA L.; GARCIA AUGUSTO F.; SORIA MARCELO A.

Villa Carlos Paz, Córdoba, Argentina

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

SAIB

BT-P03. Abstract Bacillus amylolyquefaciens BNM122 showed antifungal activity against several phytopathogenic fungi. To effectively use this strain as a biocontrol agent for soybean, a formulation that ensures an adequate shelf-life and maximal controlling capabilities is needed. Since B. amyloliquefaciens is a spore-forming species, one of the first design decisions is whether to use living cells or spores. Soybean seeds produce exudates that negatively affect the survival of other microbial inoculants. We tested the survival of exponentially growing cells and a mixture of stationary-phase cells and spores on seeds. Older cultures were little affected by seed exudates, while younger cells were sensitive. Another requirement that inoculants must meet is the tolerance to the sudden dehydration that occurs when the product contacts its target. Again, stationaryphase cultures were more resistant. Additives that protect from osmotic shock (alginate, guar and xanthans gums) increased 10 times the survival of spores, but had no effect on younger cells. Bacilli spores are tolerant to UV-B light, but it was necessary to demonstrate that they could tolerate the higher doses of radiation recorded in the summer months of the Southern hemisphere. We observed that the equivalent titre of cells on soybean leaves increased from 3x107 to 4x107 cfu.ml-1 after six days of exposition to UV-B in a culture chamber.