FIG.1.

Detection of R. solanacearum biovar 2 cells by direct isolation on modified SMSA medium during a survey of the Tormes river in northwest Spain from March 2000 to August 2001. Water samples were collected at five sites (1 to 5) on the river at different distances, both upstream and downstream, from a confirmed potato outbreak. Sampling sites were numbered according to their location from the first site as follows: first sample site (0 km), second site (3 km), third site (6 km), fourth site (9 km), and fifth site (12 km). The potato field was equidistantly located between sites 2 and 3. The dates indicate the sampling months during the years 2000 and 2001. The populations of R. solanacearum (from 0 to 80 CFU/ml) and the river temperatures at the time of water sampling are indicated in the figure.