Contrasting physiological responses to iron deficiency in Cabernet Sauvignon grapevines grafted on two rootstocks

The present work aimed to compare the physiological responses to Fe deficiency in Vitis vinifera L. cv. Cabernet Sauvignon grafted on two Vitis rootstocks with different Fe chlorosis susceptibility: 110 Richter (moderately tolerant) and 3309-C (susceptible). Plants were grown in hydroponic solutions with 50 M of Fe-EDTA or without Fe. Our data showed that, in a first step (18 days after treatment, DAT), Fe deficiency reduced net photosynthesis in leaves from both variety/rootstock combinations, without modifying leaf chlorophyll concentration. Moreover, Fe deficiency increased the activity of PEPC and NADP+-IDH enzymes and the concentration of malic and total organic acids in roots of both rootstocks. During such period, no differences related to Fe level were recorded in the main shoot length and biomass. After a longer exposure to Fe deficiency (32 DAT), the activity of PEPC and organic acid-linked enzymes in roots of both genotypes remained unaltered. However, at 32 DAT, plants grafted on 110 Richter reacted to Fe deficiency by reducing the main shoot length and biomass, whereas such reduction was not observed in plants grafted on 3309-C. In addition, at 32 DAT Fe deficiency reduced the net photosynthesis as well as the chlorophyll concentration in plants grafted on 3309-C, without modifying these parameters in 110 Richter plants. In conclusion, our results revealed significant differences between the two variety/rootstock combinations in severity of Fe deficiency symptoms and physiological responses