Fruit Ripening Has Little Influence on Grapevine Cold Acclimation

Abstract

This four-year study tested whether the physiological demand of fruit ripening may interfere with grapevine cold acclimation in autumn or with midwinter hardiness. Three harvest time treatments were established in a mature vineyard of own-rooted Cabernet Sauvignon vines: clusters were removed after fruit set, at veraison, or after the first fall frost. Average yield of the late harvested vines varied from 4.2 to 5.1 kg/vine (7.5 to 9.2 t/ha) among years, and soluble solids varied from 23.4 to 25.6 Brix. The presence of fruit during ripening delayed leaf senescence, measured as chlorophyll decline. The fruit also tended to delay the senescence-associated decrease in photosynthesis. All vines showed typical patterns of autumn cold acclimation, midwinter hardiness, and spring deacclimation. Cold hardiness of buds, cane phloem, and cane xylem varied during winter depending on prevailing temperature, and during the coldest winter reached levels of -27°C for 50% bud damage and -28°C for the onset of xylem injury. Early fruit removal had no effect on cane nonstructural carbohydrates and, with few exceptions, failed to enhance cold hardiness. Depending on the year, early fruit removal improved bud hardiness on 5 to 15% and xylem hardiness on 8 to 38% of all measurement dates. On those dates, the early harvested vines tended to be 1 to 2ºC hardier than the late harvested vines, irrespective of the time of crop removal. No trend was found for phloem hardiness. These results indicate that cropping, at least within commercially acceptable limits in regions with sufficiently long or warm growing seasons, rarely impacts cold acclimation and maximum hardiness. Grapevines appear to adjust seasonal leaf physiology to meet their carbon demand for both fruit ripening and cold acclimation.

Clone and Rootstock Interactions Influence the Cold Hardiness of Vitis vinifera cvs. Riesling and Sauvignon blanc

“…Seasonal variations were also expected since the temperatures in the days preceding sampling dates impact cold hardiness during maximum hardiness (Proebsting et al 1980). Partial deacclimation and reacclimation have been observed in every year of this study and have been noted previously (Keller et al 2014). These patterns were more frequent in Sauvignon blanc, particularly in the 2016/17 and 2017/18 dormant seasons, putting this cultivar at a greater risk of cold damage following the brief deacclimation periods.…”

Mitigating grapevine winter damage in cold climate areas

“…Activities that promote acclimation are a reduction in the nutrient use (for example, elimination of late compost applications; Westover 2006) after the fruitset to reduce the vegetative growth, elimination of irrigation post-veraison, avoiding top hedging at least three weeks before harvest, removing any grow-tubes around the trunks in mid-August to give enough time for the trunk acclimation, and thinning the excessive crop by cluster thinning at veraison (Rahemi 2016). However, Keller et al (2014) reported that the early fruit removal of vines with a commercially acceptable yield did not impact the cold acclimation on the grapevines tested in Washington state.…”