The colonization of maize seedling roots and rhizosphere by Fusarium spp. in Mississippi in two soil types under conventional tillage and no-tillage systems

Pioneer 3167 hybrid maize was planted on two soil types in Mississippi on f our dates annually from 1995 to 1997 and was sampled at weekly intervals be ginning one week and ending 4 weeks after planting. Plots were either tille d with a do-all and rows formed in the fall or were left undisturbed until planting in the spring. Under tillage, Fusarium spp, were isolated most fre quently at the earliest and latest planting dates when seedlings were sampl ed at 10 and 17 days. In no-tillage plots, the overall isolation frequency was lower than in conventional-tillage plots and decreased with later plant ing dates and sampling times. The highest Fusarium populations were found i n the rhizosphere of a silt loam in conventional-tillage plots when seedlin gs were sampled 28 days after the second planting in 1997, compared to popu lations from a silty clay soil. Fusarium moniliforme, F. solani and F. oxys porum were the predominant Fusarium spp, isolated from maize seedling roots . In pathogenicity tests, F. moniliforme and F. solani produced measurable effects on maize seedlings. F. moniliforme reduced the length of primary ro ots and decreased the number of secondary roots, and F. solani reduced root dry weight of maize seedlings.