Three species of arbuscular mycorrhizal fungi namely, Glomus mosseae, G. fasciculatum and G. intraradices and a mixture of all three species procured from Turan Biotech Co., Shahroud, Iran, were utilized. The rooted vines were transplanted in 8 l plastic pots in 1:1 fine sand:leaf mold. While transplanting, inoculation was performed by incorporating 100 g expanded clay containing spores, mycelium, and infected/colonized Trifolium repens L. root fragments near the roots of each plant. The control plants were not inoculated. The plants were kept in greenhouse at 35/25 ℃ day/night temperatures and 70% relative humidity. Ninety days after inoculation AMF root colonization was confirmed by staining fresh root segments, according to procedure suggested by Phillips and Hayman (1970). Fresh grape leaf and stem tissues (Vitis vinifera L.) were harvested from the inoculated and non-inoculated vines and transferred to the laboratory for analysis.

Grape plants inoculated with AMF (Glomus sp.) would make higher quercetin content than non-mycorrhizal grape plants. However, the response was found to be depending on grape genotype.