Biocontrol and population dynamics of Fusarium spp on wheat stubble under field conditions

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

Mendoza

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

UNRC, ISM, Mycored

Antagonistic fungi applied to crop stubbles may reduce survival and multiplication of pathogens present in the residues and favor disease control. The biocontrol activity of Clonostachys rosea (strains 1 and 2) was evaluated by applying conidial suspensions at two levels on wheat stalks (Treatments T1 to T4). Fusarium graminearum (Fg), F. avenaceum (Fa) and F. verticillioides (Fv) were quantified by TaqMan PCR over a period of 6 months in two years at two locations (Marcos Juárez and Río Cuarto). Additionally, pathogen population dynamics were studied at one location (Río Cuarto) during one year. Pathogen populations of Fa and Fv showed no change after 6 months of exposure, but Fg population significantly decreased after 3 months and was not detected after 6 months at both locations in the control trials. At Río Cuarto, biocontrol effect after 3 months was only observed for Fg and, after 6 months, Fa and Fv populations were diminished in two of the four treatments. At Marcos Juárez, biocontrol effect was observed in T1, T3 and T4 for Fg and Fa and only in T3 for Fv after 3 months of exposure. Control treatments of Fa and Fv remained stable after 6 months and biocontrol effect was observed in T3 and T4 for Fa and in T2 and T3 for Fv. Fg population decreased to undetectable levels after 6 months, so no biocontrol effect of Clonostachys rosea strains were possible to evaluate. Population dynamics of the three pathogens on wheat stubble were evaluated at Río Cuarto during January-July 2011. Sampling was done at the beginning of the experiment (January 20th) and after 15, 30, 60, 90 and 180 days. Fa and Fv populations remained unchanged after 90 days and no significant differences were observed between quantifications of these pathogens at 90 and 180 days. Fg decreased from the first to the 15 days sampling and maintained stable till 60 days. After 90 days, Fg decreased again and no detection was possible after 180 days. During the trial, weather conditions variations were observed. In the first 90 days, mean temperature was 19.8 ºC and from 90 to 180 days, was 10.9 ºC. Precipitations during the trial reached 420 mm, with 230 mm after the first 30 days. Stalks humidity ranged from 15 % at the beginning of the trial to 60 days, but after 90 days, stalk humidity decreased to 5 %. The highest relative humidity was recorded during the first 15 days and averaged 67 %. Clonostachys rosea (strain 2) showed better biocontrol effect on the three pathogens evaluated. Wheat stalks were adequate as a reservoir for Fa and F. V populations while, under our field conditions  were unfavorable for F. g