Vine performance and leaf physiology of conventionally and minimally pruned Sangiovese grapevines

Abstract

A three-year-study (1996-1998) was carried out on field-grown Sangiovese grapevines under the temperate, humid climate of the Po Valley (northern Italy) to assess their degree of adaptation to minimal pruning (NIT) as compared to conventional pruning (CP). Evaluation included canopy growth, yield, berry ripening and grape rot incidence. In 1996 leaf function was determined as net assimilation (A); seasonal total canopy light interception and percentage of canopy gaps were also measured.
As compared to CP, over the 3-year period MP showed typical features of a more rapid canopy development and earlier growth cessation, higher shoot number with shorter shoots and smaller leaves, higher yields with smaller and looser clusters less susceptible to bunch rot. Must sugar concentration was significantly lowered.
Seasonal rates of A recorded on single leaves of the two pruning treatments at different shoot positions were overall similar except for higher A in young MT leaves having a chronological age of about 8-10 d. MP also showed the tendency of retarded leaf senescence. The seasonal total light interception trends indicated a linear increase with formation of leaf area in CP, whereas total fight interception in MT augmented until about 50 % of canopy filling and then remained constant with further leaf area development. This suggests that about half the leaf area produced in the MP vines contributed mostly to mutual shading rather than enhancing light interception capability, and, hence, photosynthetic capacity.
The overall data indicate that a satisfactory balance in the minimally pruned Sangiovese grapevines can only be reached with further adjustments of crop level to be performed either as partial winter and/or summer pruning. Nevertheless, in MP vines the consistent feature of looser clusters which are much less susceptible to bunch rot is crucial in an area usually characterized by abundant rainfall at pre-harvest.