| Autor: |
Machado FJ; Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa MG, Brazil.; Department of Plant Pathology, University of Kentucky, Lexington, KY, U.S.A., Kuhnem PR; Programa de Pós-graduação em Fitotecnia, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Porto Alegre RS, Brazil., Casa RT; Universidade do Estado de Santa Catarina, Lages SC, Brazil., McMaster N; School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, U.S.A., Schmale DG 3rd; School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, U.S.A., Vaillancourt LJ; Department of Plant Pathology, University of Kentucky, Lexington, KY, U.S.A., Del Ponte EM; Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa MG, Brazil. |
| Abstrakt: |
In Brazil, Gibberella ear rot (GER) of maize is caused mainly by Fusarium meridionale , whereas F. graminearum is a minor contributor. To test the hypothesis that F. meridionale is more aggressive than F. graminearum on maize, six experiments were conducted in the south (summer) and one in the central-south (winter), totaling seven conditions (year × location × hybrid). Treatments consisted of F. graminearum or F. meridionale (two isolates of each) inoculated once 4 days after silk, inoculated sequentially and alternately ( F. graminearum → F. meridionale or F. meridionale → F. graminearum ) 6 days apart, or (in the central-south) inoculated sequentially without alternating species ( F. meridionale → F. meridionale or F. graminearum → F. graminearum ). Overall, severity was two times greater in the south (37.0%), where summer temperatures were warmer (20 to 25°C) than in central-south. In the south, severity was greatest in F. meridionale treatments (67.8%); followed by F. meridionale → F. graminearum (41.1%), then F. graminearum → F. meridionale (19.4%), and lowest in F. graminearum (2.1%), suggesting an antagonistic relationship. In the central-south (15 to 20°C), severity was generally higher in the sequential nonalternating inoculation treatments ( F. meridionale → F. meridionale or F. graminearum → F. graminearum ) than when either species was inoculated only once. Only nivalenol (NIV) or deoxynivalenol was detected when F. meridionale or F. graminearum , respectively, was inoculated singly, or sequentially with no alternation. Both toxins were found in grains harvested from the F. meridionale → F. graminearum treatment, whereas only NIV was found in kernels from the F. graminearum → F. meridionale treatment, suggesting that F. meridionale was more competitive than F. graminearum in coinoculations. The dominance of F. meridionale as a cause of GER in Brazil may be due in part to its higher aggressiveness and competitiveness compared with F. graminearum . |
