Abstract:A study was conducted to determine the key environmental and viticultural variables affecting the concentration of 3-isobutyl-2-methoxypyrazine (IBMP) in Cabernet franc grapes. Berries were sampled from individual vines at 30 days after anthesis (DAA), 50 DAA, and harvest from 10 and Important variables identified for modeling IBMP at 50 DAA were those associated with vine vigor, which was positively correlated with IBMP accumulation. Cluster light exposure did not explain differences in IBMP accumulation across sites, but it was important for modeling smaller differences within some sites. IBMP decrease could not be satisfactorily modeled across multiple sites, but within sites the decrease was most consistently correlated with classic fruit maturity indices (total soluble solids [TSS], TSS*pH 2 ). The intensity of herbaceous aromas in wines produced from each site was not correlated with IBMP concentration, but multivariate models indicated that lower vine water status was the best predictor of increased herbaceousness.

Bunch grapes (Euvitis) are classified as moderately salt-tolerant. However, little is known about the salt tolerance of muscadine grapes (Vitis rotundifolia). The objective of this research was to evaluate the salt exclusion capacity of muscadine grapes relative to common bunch grape rootstocks and hybrid winegrapes using a greenhouse screening assay. In two separate experiments, 31 muscadine, six bunch grape rootstocks, and five hybrid winegrape cultivars were irrigated daily with a 25-mm sodium chloride salt solution for a period of 14 d, followed by a destructive harvest to determine sodium (Na) and chloride (Cl) concentrations in root and shoot tissues. Generally, the muscadines studied exhibited a greater range of salt concentration relative to bunch grape rootstocks. Total tissue (shoot and root) salt varied by 250% and 430% across muscadines and by 180% and 190% across bunch grape rootstocks for Na and Cl, respectively. Despite the wider range, muscadine grapes expressed significantly less leaf necrosis than the bunch grape rootstocks. The most effective salt-excluding muscadines, ‘Janebell’, ‘Scuppernong’, ‘Late Fry’, and ‘Eudora’, were not distinguishable from the bunch grape rootstocks [‘Paulsen 1103’ (1103P), ‘Ruggeri 140’ (140Ru), ‘Schwarzmann’, ‘Millardet et de Grasset 101-14’ (101-14 Mgt.), ‘Millardet et de Grasset 420A’ (420A), and ‘Matador’]. Overall, there was no discernable difference between the salt exclusion capacity of muscadine and bunch grapes. The hybrid winegrape ‘Blanc Du Bois’ displayed poor Na and Cl exclusion properties but showed only moderate leaf necrosis symptoms. In both experiments, ‘Blanc Du Bois’ accumulated more than two-fold higher root and shoot concentrations of Na and Cl compared with the best-performing rootstocks (1103P, 140Ru, 101-14 Mgt.), suggesting that ‘Blanc Du Bois’ could benefit from grafting if salinity is a limiting factor.

No abstract

Tempranillo is the second most planted variety in Texas. However, over-cropping can be an issue. Crop load can be managed by pruning and mechanical fruit thinning. Mechanizing fruit thinning provides three benefits: yield reduction, berry thinning to decrease cluster compactness and reduce fungal disease and lower production costs than fruit thinning by hand (Tardaguila et al., 2008). In this study, crop load was manipulated by pruning and mechanical fruit thinning and its effect was determined on berry and wine quality.

‘Blanc Du Bois’ (Vitis spp.) is the most widely grown Pierce’s disease tolerant white grapevine cultivar in Texas. As an interspecific hybrid, its growth habit is seimi-drooping, and 'Blanc Du Bois' is characterized as vigorous. This study evaluated the impact of training system (Mid-Wire Cordon with VSP, Mid-Wire Cane with VSP and Smart-Dyson, High-Wire Quadralateral, and Watson) on 'Blanc Du Bois' growth, yield components, and fruit composition at two locations in Texas. The first site was located in the Rio Grande Valley where the mean extreme minimum winter temperature is -1.1 to 1.7° C (USDA Cold Hardiness Zone 10a). As a result of climate and site conditions, vine size, determined by dormant pruning weight, was very large averaging from 3.71 to 5.56 kg per vine across training systems over a three-year period. At this site, the horizontally divided systems, High-Wire Quadrilateral and Watson were the highest yielding averaging 10.66 and 7.49 kg per vine, respectively, as a result of more shoots per vine, and higher fruitfulness. The Mid-Wire Cordon and Mid-Wire Cane Pruned Training Systems had lower yields in two out of three years, but fruit maturity indices soluble solids and pH reflected more advanced maturity at harvest. At the second site, located in the Central Gulf Coast of Texas (USDA Cold Hardiness Zone 8b), vines were less vigorous with pruning weights averaging 1.66 to 1.83 kg per vine across training systems over three years. Consistent differences in yield components, vine size, and fruit composition were not observed, and all the three training systems under study had acceptable growth and fruiting characteristics. The results of this research suggest that 'Blanc Du Bois’ vigor potential and growth habit makes it well-suited for horizontally divided canopy training systems, particularly on vigorous sites.

No abstract

Two-year-old, field-grown golden kiwifruit (Actinidia chinensis) and fuzzy kiwifruit (Actinidia deliciosa) plants were evaluated for injury following an early freeze event of −4.1 °C on 14 Nov. 2018 in Burleson County, TX. Plant material included seven cultivars: one seed-propagated [Sungold™ (ZESY002)] and three cutting-propagated golden kiwifruit (AU Golden Dragon, AU Golden Sunshine, CK03), and one seed-propagated (Hayward) and two cutting-propagated fuzzy kiwifruit (AU Authur and AU Fitzgerald). Observations were made 5 weeks after the frost event. Base trunk diameter (BD) and maximum trunk diameter damaged (MDD) provided a reference of plant size and crude measurement of damage intensity, as evident by presence of water-soaked necrotic and/or dehydrated tissue following the removal of a thin slice of periderm, vascular cambium, phloem, and xylem. Percent of base diameter damaged (PBDD) was calculated as MDD divided by BD and provided an assessment of damage, unbiased by plant size. Percent of shoot damaged (PSD) was visually evaluated as the percentage of entire shoot system exhibiting damage. In addition, presence of basal damage (DB) and basal cracking (CB) were recorded. A strong cultivar response was observed for BD, MDD, PBDD, and PSD. Mean cultivar values for PSD ranged from 79% and 19% for AU Authur and Sungold™ seedlings, respectively, which represented extremes among cultivars. Fuzzy kiwifruit exhibited greater injury (PBDD, PSD, DB, and CB) as compared with golden kiwifruit cultivars. Basal damage and basal cracking proved unique to fuzzy kiwifruit, as DB ranged from 0% in Sungold™ seedlings to 100% in fuzzy kiwifruit ‘AU Authur’ and ‘AU Fitzgerald’. In spite of having greater vigor, golden kiwifruit plants sustained less injury. Method of propagation had no effect on injury. PBDD and PSD proved to be reliable field assays for documenting injury, based on their strong correlation value (r = 0.92). Greater relative autumn frost tolerance of golden kiwifruit over fuzzy kiwifruit cultivars is previously unreported.

Muscadine (Muscadinia rotundifolia) grapes have been used in grape variety and rootstock development due to their inherent pest and disease resistance, but little is known about their alkaline soil tolerance. In this study, Muscadine varieties, commercialrootstock and interspecific hybrid grape (Vitis spp.) cultivars were evaluated for alkaline soil tolerance under field conditions to determine the potential suitability of muscadines for rootstock development. Thirty-one muscadine and eleven interspecific hybridgrape cultivars were grown in a moderately alkaline soil (pH = 8.1) over a three-year period. Alkaline soil tolerance wasdetermined by relative vine vigour (shoot length), vine nutrient status (whole leaf tissue testing) and visual chlorosis. Additional data were collected on the timing of budbreak. Overall, the muscadines studied expressed low vigour and had greater chlorosissymptoms than the interspecific hybrid rootstocks (Paulsen 1103, Millardet et de Grasset 101-14, Millardet et de Grasset 420A,Ruggeri 140, Schwarzmann, and Matador). These parameters were not correlated with the concentration in any specific nutrient, although nutrient deficiencies (nitrogen, copper) and excesses (calcium, boron) were observed in the muscadine varieties.Overall, the muscadine grapes expressed poor alkaline soil tolerance compared to interspecific hybrid grape rootstocks (1103P, 101-14 MGt., 140Ru, Schwarzmann, 420A, and Matador), even the ones having poor alkaline soil tolerance (101-14 MGt., Schwarzmann) and own-rooted cultivars (Black Spanish, Blanc Du Bois, Dunstan’s Dream and Victoria Red). Nevertheless, some variability in chlorosis symptoms and nutrition was observed across the muscadine group, suggesting some interests to select Muscadine hybrid rootstocks less sensitive to iron chlorosis.