Chlorosis occurrence, natural arbuscular-mycorrhizal infection and stilbene root concentration of ungrafted grapevine rootstocks growing on calcareous soil

Ungrafted rootstocks of fifteen grapevine genotypes with considerable resistance and susceptibility to lime-tolerance [iron (Fe) deficiency chlorosis] were grown outdoors in pots with a fine, mixed (calcareous) mesic Typic Ustorthents soil, to determine the correlation between degree of lime-tolerance, natural arbuscular mycorrhizal (AM) infection, and AM infection relationship with root levels of stilbenes (antifungal compounds). During the second year of growth, shoot length was measured and degree of chlorosis symptoms was evaluated four times as SPAD readings. At the end of the growing season, shoot and root dry weight, root length, AM infection, root concentration of stilbene compounds (tuans- and cis-resvaratrol, epsilon -viniferin, pterostilbene) were determined. The most significant findings were: a) a negative correlation between degree of chlorosis and natural AM infection (expressed as total length of infected roots per plant); b) no significant correlation between AM infection and root stilbene concentration for the different rootstocks; c) positive relationship between chlorophyll leaf concentration and root dry weight, and d) a negative correlation between epsilon -viniferin root level and shoot dry matter.