Biological control and dynamics of Fusarium graminearum on wheat stubble during wheat-soybean in Argentina.

PALAZZINI, J.M.; YERKOVICH, N.; BARROS, G.G.; TORRES A.M.; CHULZE, S. N.

Medellin

Congreso; VIII Congreso Latinoamericano de Micología; 2014

Sociedad Latinoamericana de Micología

The biocontrol effect of Bacillus subtilis RC 218 and Streptomyces sp. 87B on Fusarium graminearum was studied on wheat stubble left in the field after harvest during a two years experiment. The experiment was done in Marcos Juarez, Argentina, in a field severely affected by a Fusarium Head Blight (FHB) outbreak during 2012. The pathogen inoculum was quantified by TaqManq PCR. Additionally, the population dynamic of F. graminearum was analyzed. During the first year experiment, B. subtilis RC 218 was applied at two level doses (104 and 106 ufc/ml) and in the second year B. subtilis RC 218 was applied only at a dose of 106 ufc/ml and a second biocontrol agent, Streptomyces sp. 87B, was evaluated at a dose of 107 ufc/ml. No biocontrol effect of B.subtilis RC 218 was observed during the two year experiment, possibly due to the high inoculum pressure initially detected in the field (1,869 pg DNA/mg). A clear biocontrol effect was observed with Streptomyces sp. 87B; after 40 days, a reduction of the pathogen inoculum was observed (82%). After three months, F. graminearum inoculum decayed to undetectable levels in the Streptomyces sp. 87B treated plot meanwhile in the control plot the pathogen was quantified at a level of 9.85 pg DNA/mg. After the 2012 FHB outbreak, time when the experiment started, high levels of F. graminearum inoculum were observed (1,869 ± 545 pg DNA/mg) and by the end of the first year experiment (6 months), a natural reduction (83.2%) was observed (313.9 ± 186 pg DNA/mg); but a similar quantification (263 ± 42 pg DNA/mg) was detected by the beginning of the second year experiment. By the end of the experiment, low F. graminearum levels were detected (9.85 ± 3 pg DNA/mg), achieving a natural reduction of 96.2%.