Biological control of Fusarium graminearum and deoxynvialenol accumulation on wheat using formulated Bacillus subtilis and Brevibacillus sp under field conditions

PALAZZINI, J.M; TORRES, A.M; CHULZE, S.N

Mendoza

Congreso; Strategies to reduce the impact of mycotoxins in Latin America in a global context; 2011

UNRC, ISM, Mycored

Fusarium graminearum is the main causal pathogen associated to head blight, a disease that affects small grain crops and causes yield losses and deoxynivalenol (DON) accumulation on grains, mainly in wheat and barley. Biological control is an important tool to reduce the disease. Two potential biological control agents (Bacillus subtilis RC218 and Brevibacillus sp.RC263) were selected in previous studies, physiologically improved by accumulation of betaine and formulated products were obtained. Dried bacteria (vegetative cells and/or spores) were tested in a field trial. Bacterial products were applied at pre-anthesis and anthesis over wheat heads and challenged with a mixture inoculum of F. graminearum strains. After 21 days, disease incidence and severity was visually estimated by using a 0- 100 % scale. At harvest, grains were collected for DON detection by liquid chromatography. Biocontrol inoculations at pre-anthesis were not effective in diminishing the disease severity, but the different treatments applied at anthesis were effective. Bacillus subtilis RC218 and Brevibacillus sp. RC263 showed significant reduction of both disease incidence and severity (below 20 %) in comparison with control treatments that showed 22 % of disease incidente and 35 % of mean disease severity. The inhibition of DON accumulation on wheat grains was also evaluated. In pre-anthesis treatments, no disease control was observed and an average of 1220 ìg/Kg of DON was detected in control and biocontrol treatments. These results showed that application of biocontrol agents at pre-anthesis is not appropriate for both disease and toxin production control. At anthesis, the average amount of DON in the control treatment was 1140 ìg/Kg and DON was not detected in biocontrol treatments. The ability of B. subtilis RC218 and Brevibacillus sp. RC263 to reduce FHB and DON accumulation was demonstrated. Further field trials are under evaluation to validate these agents.