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Timely Information > Posts > Development and Productivity of Pierce’s Disease Resistant Vitis vinifera Grape Selections in Central Alabama.

Alabama, gifted with a warm growing season and many sunny days, has the opportunity to successfully produce numerous fruit crops ranging from peaches to blueberries. However, until recently, viticultural producers have been restricted to growing native muscadines and hybrid bunch grapes due to the looming presence of Pierce’s Disease (PD), caused by Xylella fastidiosa, an endemic xylem clogging bacterium that is deadly to susceptible Vitis vinifera (European) grapevines.


 A       B



Figure 1 A, B. Ripening clusters of V. vinifera selection ‘502-01’ within fruiting zone of a VSP trained vine (A) and high productivity of early season selection ‘502-10’ (B) at the Chilton REC, AL, 2015.


The U.C. Davis grape breeding program, in response to the spreading threat of PD, is working to develop and release high quality PD resistant V. vinifera bunch grapes. Three of these experimental 87.5% V. vinifera PD resistant selections were obtained and planted in 2010 at an experimental vineyard at the Chilton Research and Extension Center (CREC) located in Chilton County, AL to examine the feasibility of growing PD resistant vines amidst Alabama’s high disease pressure environment. Due to the promise observed in previous years’ preliminary results, more detailed research is now being conducted to assess the phenological, physiological, and fruit characteristics for the three experimental V. vinifera PD resistant selections: ‘502-10’, ‘502-01’, and ‘501-12’.


A new crop for Alabama, V. vinifera vines are trained in a different manner than muscadine grapes. The training system facilitates the upright growing habit of V. vinifera grapes. Rather than allowing fruiting canes to grow downwards, V. vinifera fruiting canes are instead trained upwards and periodically directed within a vertical shoot positioning (VSP) system. This training system facilitates efficient pest management practices, while concentrating the crop load within a compact fruiting zone (Fig. 1 A).  


Studying the vines’ development throughout the growing season allows for development of proper management techniques in a given set of environmental conditions. For the three selections, bud break had occurred by the first week of April and canopy formation and establishment were completed by April 20th in 2015. Flowering was initiated in the first days of May, and all selections were considered in full bloom within a week.


Veraison is the stage associated with grape ripening. It starts when the berries start turning their color from green to black or fully colored berry, and sugar accumulation increases. Veraison takes about 40-50 days depending on the particular cultivar and continues until harvest. The three selections studied varied in color accumulation timing, with ‘502-10’ being fully colored in July. As a result, ‘502-10’, was harvested in mid-August. The remaining two selections finished fully developing their berry coloration in early October. 


The early ripening selection ‘502-10’, produced an average yield per vine of 24 lb. Based on the planting distance of 7 X 12, this translates to a yield of approximately 6 tons per acre, though crop load manipulation is a factor that will need to be determined in a site specific context to ensure maximum fruit quality (Fig. 1 B). With healthy clusters averaging roughly a pound per cluster, the vine ripened fruit can be processed into juice or wine, high in health promoting antioxidants such as anthocyanin and resveratrol.


Regionally produced grapes are a critical component of local juices and wines. We look forward to the upcoming harvests so that we can share more about the quality and yield of these three unique selections possessing innovative traits such as PD resistance, opening the doors for V. vinifera roots in southeastern soils.






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