Effects of leaf removal and topping on 'Syrah' grapevine in the tropical semi-arid region of Brazil

P.C. de S. Leao, A.R.L dos Santos, D.A.R. Gonҫalves, J.P.D. Costa
The wines of the Sao Francisco Valley, in the northeast of Brazil, are the only ones in the world produced under semi-arid tropical conditions. This study shows results related to the 4th production cycle for the physiological and agronomic traits of the 'Syrah' grapevine subjected to the practices of defoliation and topping. The experiment was carried out in 2012 in a commercial vineyard of the 'Syrah' cultivar grafted onto the rootstock 'IAC 766' drip irrigated for five years. Treatments consisted of combinations of the practices of leaf removal of basal leaves above the last bunch, applied once at the beginning of the berry touch stage, and shoot topping applied in two stages: 'pea'-sized grain and the beginning of berry touch. The control (T1) consisted of the same canopy management adopted on the farm, which was two leaf removals and one early topping. The experimental design was randomised blocks with four replications. The fresh matter weight of shoots was not affected by leaf removal and topping, although the leaf fresh matter weight differed significantly among treatments. Plants subjected to treatment T2, leaf removal and no topping showed greater production than those subjected to T5, leaf removal and topping in stage 1. Greater mass of the bunch was obtained in T8, with no leaf removal and topping in stage 1. The average Ravaz index was 7.5, showing a good balance between vegetative growth and fruits. The effects of leaf removal and shoot topping on gas exchange were analysed through photosynthesis, stomatal conductance and water use efficiency after 15 days of treatment application until the ripening stage using IRGA (model Li -6400 XT). From the standpoint of leaf gas exchange, leaf removal and shoot topping practices did not affect the plants. It is up to the grower to adopt the technique that leads to lower operating costs by ensuring good photosynthetic rates and, consequently, improved grape quality for winemaking.
Leao, P.C. de S., dos Santos, A.R.L, Gonҫalves, D.A.R. and Costa, J.P.D. (2017). Effects of leaf removal and topping on 'Syrah' grapevine in the tropical semi-arid region of Brazil. Acta Hortic. 1157, 351-356
DOI: 10.17660/ActaHortic.2017.1157.49
Vitis vinifera L., summer pruning, grape, leaf removal, physiology

Acta Horticulturae