Long-term survival of Plasmopara viticola oospores

Abstract: A research was carried out in order to verify the long-term viability of Plasmoparaviticola oospores. It is commonly assumed that oospores may survive across grapevines growingseasons, but no experimental evidence of this assumption has been provided to date. Grapevineleaves were collected from untreated plants in Emilia-Romagna in fall 2004 to 2008. Fragmentsof these leaves were kept in soil under natural conditions. In spring 2005 to 2009, part of the leaffragments collected in the previous autumn were used to evaluate oospore germination using thefloating disk bioassay; in spring 2009, the bioassay was also performed using the leaf residuecollected in fall 2005 to 2007. Results demonstrated that P. viticola oospores remained viable forthe whole period considered in this work, i.e., about 65 months (from fall 2004 to spring 2009).