Plasmopara viticola infection process and accumulation of important stilbenes in some grapevine varieties grown in Turkey and in individuals for brined leaves

The detached leaves of three Turkish grapevine varieties (cv. Karasakiz, cv. Muskule and cv. Tekirdag Sultani) and three hybrid individuals for brined leaves (119, 154, 200) with different resistance levels to downy mildew (Plasmopara viticola) based on sporulation area (mm(2)) were examined for sporangia number at 7 days, progress of the pathogen and stilbene production at different times after inoculation. A significant positive correlation was determined between number of sporangia on the lesion and sporulation area. The lowest number of stomata infected by the pathogen at 48 h after inoculation (hpi) was determined in extremely resistant 200, followed by highly resistant cv. Muskule and 154. Vesicles of the pathogen were observed in leaves of all tested plants at 15 hpi; however, in 200 the vesicle primary hypha, which developed at 72 hpi, did not elongate into intercellular spaces of the mesophyll after that time. Elongation occurred in 119 (resistant) at 48 hpi and in cv. Muskule and 154 at 72 hpi, but development of the pathogen was restricted to 72 hpi. Pathogen mycelia covered the intercostal fields in sensitive (cv. Karasakiz) and highly sensitive (cv. Tekirdag Sultani) varieties at 72 hpi. The amount of resveratrol was found to be high in resistant types, while the highest amount of epsilon-viniferin was determined in 200 at 72 hpi. Cv. Muskule and 154 contained higher amounts of pterostilbene than 119. These new results underline the role of epsilon-viniferin in 200 and pterostilbene in cv. Muskule and 154 in high resistance toward P. viticola and the importance of these grapevine types in downy mildew management.