Vegetative, physiological and nutritional behavior of new grapevine rootstocks in response to different nitrogen supply

Viticulture is in great need of new rootstocks sharing features of scion growth control and tolerance to\r\nmajor biotic and abiotic stress factors. A two year study was carried out in pots to assess performances\r\nof the two new M1 and M3 rootstocks vs. those of the commercial rootstocks 1103P and 101-14. Potted\r\nvines of M1, M3, 1103P and 101-14 rootstocks were grown in a calcareous and non calcareous soil and\r\nfor two consecutive seasons subjected to three N supply levels at 0, 2 and 4 g of N per pot. Vegetative\r\ngrowth, leaf gas exchange, leaf greenness index (GI) and leaf blade nutrition were assessed. M1 and 1103P\r\nwere the least vigorous genotypes in terms of total pruning weight; M1 also manifested a stronger apical\r\ndominance. Both M rootstocks and 101-14 showed increased leaf WUE at both N supply levels which\r\nwas due to ability to maintain, at increasing N supply, similar leaf assimilation rates while significantly\r\nreducing leaf transpiration. Common tendency of any rootstocks was that increasing N supply corresponded\r\nto lowered leaf concentration of K, P, Mg and B. M1 was able to combine a series of desirable\r\nfeatures including lower vigor, strong apical dominance, higher WUE at increasing N supply and quite\r\nwell balanced leaf nutritional pattern. In the present trial M3 did not have the expected devigorating\r\neffect.