Preveraison Leaf Removal Changes Fruit Zone Microclimate and Phenolics in Cold Climate Interspecific Hybrid Grapes Grown under Cool Climate Conditions

Abstract

Changes in grape cluster microclimate during ripening have been explored extensively across Vitis vinifera cultivars, but there is limited information about its effect on cold climate interspecific hybrid grape (CCIHG) cultivars grown under cool climate conditions. The influence of a single preveraison leaf and lateral shoot removal (“exposed”) treatment on fruit zone microclimate and juice total phenolic concentration (TPC), monomeric anthocyanin concentration (MAC), and percent polymeric color was evaluated in the white cultivars Brianna and La Crescent and the red cultivars Frontenac, Marquette, and Petite Pearl over three consecutive growing seasons and in their respective wines in the last year of the study. Treatment effect on juice TPC in the white cultivars was cultivar-dependent, and there was no detectable treatment effect on wine TPC. For the red cultivars Frontenac, Marquette, and Petite Pearl, the exposed treatment increased the TPC, MAC, and percent polymeric color in the wines. The beneficial influence of the exposed treatment on MAC, TPC, percent polymeric color, and titratable acidity was associated with increased berry temperature and photosynthetically active radiation in the fruiting zone. The cultural practice of a single preveraison leaf and lateral shoot removal may be an effective strategy to improve red wine color stability of CCIHG cultivars grown under cool climate conditions.