| Popis: |
In a German vineyard (PRO) between 10 and 13 June 2004, the incidence of grapevine downy mildew (Plasmopara viticola) increased abruptly from 0 to 99%. Infected vines bore on average between 45 and 60 lesions each, corresponding to about 220 000 lesions ha−1 in a non-aggregated distribution. A second vineyard (FUT), approximately 50 m distant from PRO, had been inoculated 3 weeks before the abrupt increase in incidence of disease in PRO. Using microsatellites to ascertain the sources of inoculum and likelihood and extent of interplot spread from FUT to PRO, 555 samples were collected and 20 unique genotypes were identified, of which one caused 80% of the sampled lesions in both vineyards. Three genotypes responsible for 95% of the lesions in FUT and PRO were identified as the genotypes originally established through earlier inoculations in FUT. This is the first report of definitive and quantitative evidence of sporangial migration up to 130 m in a single infection event. The utility of molecular tools to address practical epidemiological issues in this pathosystem is illustrated. The results of this study provide an example of how P. viticola was able to rapidly colonize European vineyards after the pathogen was introduced from North America in 1878. |
