EFFECT OF THE ROOTSTOCK ON THE OCCURRENCE OF LIME-INDUCED CHLOROSIS OF POTTED VITIS-VINIFERA L CV PINOT BLANC

The chlorosis susceptible Vitis vinifera L. cv. 'Pinot blanc' was grafted on two hybrid rootstocks with different iron efficiency, as follows: V. Berlandieri x V. rupestris '140 Ru' (iron-efficient) and V. riparia x V. rupestris '101-14' (iron-inefficient). The grafted vines were grown in pots of a calcareous and a non-calcareous soil. The shoot growth was periodically checked and leaves, selected at two different times (at the middle of the annual growing period), were assayed for total chlorophyll, ferrous iron, ash alkalinity, percentage of dry matter and chlorosis score. At the end of the growing cycle the roots were oven-dried and weighed. The most significant findings of the trial were: (a) the soil strongly affected the shoot growth, with canes about twice as long in the non-calcareous soil; (b) the iron-efficient rootstock ('140 Ru') did not induce chlorosis when growing on the calcareous soil, while the opposite occurred with the iron-inefficient rootstock ('101 = 14'); and (c) a high ash alkalinity occurred in light chlorotic leaves compared to green ones, under the same iron concentration.