Photosynthetic gas exchange and functionality in different grapevine cultivars and their cross grafted combinations in response to bicarbonate-induced Fe deficiency

Iron (Fe) deficiency-induced chlorosis can be a serious problem in grapevine cultivation. Measuring genotypic tolerance to this disorder is of vital importance in rootstock selection. In this research, different sources of Fe (FeSO 4 ·7H 2 O and FeEDTA) were used and their effects were evaluated on the response of a tolerant (‘Thompson Seedless’) and a sensitive (‘Flame Seedless’) grape cultivar. Also, their cross-grafted combinations [‘Flame Seedless’/’Thompson Seedless’ (FS/TS) and ‘Thompson Seedless’/‘Flame Seedless’ (TS/FS)] were evaluated for tolerance to Fe deficiency. Bicarbonate (30 mM) was used for inducing iron deficiency in the plants. Despite the negative effects of bicarbonate, the ‘Thompson Seedless’ maintained a significant chlorophyll index, compared to the ‘Flame Seedless’ cultivar. Gas exchange measurements showed that the bicarbonate had more adverse effects on photosynthesis and water-use-efficiency (WUE) in the ‘Flame Seedless’ cultivar. Despite the bicarbonate toxicity, the photosynthetic system of the FS/TS graft combination showed no significant change in FV/FO, whereas adverse effects occurred significantly in ‘Thompson Seedless’, ‘Flame Seedless’, and their TS/FS graft combination. Bicarbonate decreased the performance index in ‘Flame Seedless’. In conclusion, scions of the susceptible cultivar performed well when grafted on tolerant rootstocks. Such grafting combinations can help plants to cope with the negative effects of bicarbonate toxicity on grapevine.