Micro-scale systematic sampling of soil:: Heterogeneity in populations of Fusarium oxysporum, F-solani, F-roseum and F-moniliforme

The variability of Fusarium spp. density in soil was studied in a held located in Badajoz (south-western Spain). The upper 40 cm of each side of a 1 m x 1 m x 1 m pit were sampled intensively, taking soil samples from points 10 cm apart. The species isolated were F. oxysporum, F. solani, F, roseum and F. moniliforme. For all four sides of the pit population densities of F. oxysporum, F. solani and F. roseum significantly decreased with increasing soil depth and for all the four layers significant differences were detected between sides of the pit. Horizontal variability also occurred on a smaller sampling scale: when a layer of a side was sampled, densities might be significantly different between points in the layer. However, no clear trend in horizontal variability was observed for any species. These findings demonstrate that Fusarium spp. populations were heterogeneously distributed in this reduced soil volume.