Biofungicide formulation based on Bacillus velezensis EM-A8 for control of maize foliar diseases

Resumen

The aim was to evaluate inoculum production of Bacillus velezensis EM-A8, a native bacterium of maize phyllosphere, antagonist to foliar pathogens Exserohilum turcicum and Puccinia sorghi. Six economic media were tested: 1) Nutrient Broth (8 g.L-1); 2) Whole soybean flour (40 g.L-1) + sucrose (20 g.L-1); 3) Whole soybean flour (10 g.L-1) + molasses (20 g.L-1), 4) Whole soybean flour (40 g.L-1) + molasses (10 g.L-1); 5) Yeast extract (10 g.L-1) + molasses (5 g.L-1) and 6) Yeast extract (10 g.L-1) + sucrose (5 g.L-1). Growth was determined spectrophotometrically at 620 nm and viability was estimated. M2 showed the shortest generation time (g 1.22 h). M3 and M5 were selected for efficiency and aW was modified with glycerol at 0.97. Inoculums were stored under refrigeration (5°C) and room temperature (20-25°C) for 8 months. At 5°C the viability of the antagonist at 3.3-4.5 log CFU ml-1 was significantly lower than at room temperature (6-6.8 log CFU ml-1), where M5 showed the highest stability. The bioformulation of B. velezensis EM-A8 in M5 at aW 0.97 and stored at room temperature will allow successful control of maize foliar diseases.

Highlights:

• Commercial products and by-products in different media provide high growth and shelf life of B. velezensis EM-A8.
• Storage temperature significantly affected B. velezensis EM-A8 viability.
• B. velezensis EM-A8 in growth medium with yeast extract and molasses, modified a_W with glycerol at 0.97 and stored at room temperature is a promising product.
• Liquid formulations stored at room temperature maintained stable viability in 6 log for 8 month.