Assessing Recently Released Rabbiteye Blueberry [Vaccinium virgatum (Ait.)] and Muscadine Grape [Vitis rotundifolia (Michx.)] Cultivars for Sustainable Production in Alabama

Abstract

Rabbiteye blueberry (Vaccinium virgatum Aiton) and muscadine grape (Vitis rotundifolia Michx.) are key fruit crops in the southeastern United States. Successful production relies on selecting cultivars adapted to local environmental conditions, such as fluctuating winter/spring temperatures, warm and humid summer conditions, and high risk of late spring frost events. This study assessed phenological development, yield potential, and fruit quality attributes of recently released cultivars of rabbiteye blueberry with improved characteristics and recently released perfect-flowered muscadine grape cultivars and selections under central Alabama conditions during the 2024 and 2025 growing seasons. Field experiments were conducted at the Chilton Research and Extension Center in Clanton, Alabama, using a randomized complete block design. The study objective was to identify cultivars with better adaptation, productivity, and fruit quality as compared to established cultivars under central Alabama conditions. Ten rabbiteye blueberry cultivars were selected for their improved traits such as delayed flowering, improved productivity, large berry size, excellent fruit firmness, good overall fruit quality and extended ripening period. The results of our trial suggest that both – the genotype and the environmental condition affect the cultivar’s phenological development. The early ripening cultivar ‘Alapaha’ initiated flowering between 3 to 6 days later than the standard ‘Climax’, providing an opportunity for reduced risk of late spring frost damage, while maintaining early fruit maturity. The early ripening ‘Vernon’ also had the longest ripening period and was highly productive. Yield per plant was significantly affected by cultivar, year, and the interaction between them, demonstrating that seasonal conditions modified cultivar performance. ‘Ochlockonee’ was consistently among the most productive cultivars in both years, whereas ‘Vernon’ produced the highest yield in 2025. Individual berry weight was influenced by both cultivar and year, with ‘Titan’ and ‘Krewer’ consistently producing the largest berries. In contrast, berry firmness was affected by cultivar, year, and their interaction. ‘Titan’ remained the cultivar with the firmest fruit in both seasons. ‘Krewer’ also produced firm berries. Soluble solids, titratable acidity, TSS:TA ratio, and pH differed among cultivars; however, most of the fruit quality traits remained within commercially acceptable ranges. Seasonal environmental conditions affected fruit quality, with increased rainfall resulting in larger berries but lower soluble solids and firmness in 2025 season. Overall, our results show that under central Alabama conditions, ‘Vernon’, ‘Ochlockonee’ and ‘Alapaha’ are high productivity choices, while ‘Titan’ and ‘Krewer’ produced large and firm berries with commercial fresh-market potential. Perfect-flowered muscadine grape cultivars planted in 2019 and advanced selections planted in 2021 were evaluated under central Alabama conditions for their phenological development, yield potential, and fruit quality attributes. The objective was to determine whether self-fertile cultivars can provide good yield with improved fruit quality, especially with large berry size, firm fruit and high sugars to acidity ratio which is highly desirable for fresh market. Among the experimental cultivars, ‘Razzmatazz’ fruit ripened very early in the season. ‘Hall’ and ‘Lane’ were early-ripening cultivars, while ‘Supreme’ and ‘Eudora’ matured mid-season. ‘Southern Home’ and ‘Paulk’ ripened late. Yield per vine varied among cultivars and was affected by cultivar by year interaction. The female cultivar ‘Eudora’ produced the highest yield in both seasons, while the yield of perfect-flowered ‘Hall’ and ‘Southern Home’ was similar to ‘Eudora’. Individual berry weight was influenced by cultivar, year, and their interaction. ‘Paulk’ and ‘Hall’ consistently produced large berries, comparable to the female standard ‘Supreme’ and consistent with breeder’s evaluation reports. The percent berries with wet stem scar was affected by cultivar, year, and their interaction and was relatively low for the studied perfect-flowered cultivars. Total soluble solids were affected by a cultivar by year interaction, while berry firmness, titratable acidity, TSS:TA ratio, and juice pH were primarily cultivar-dependent. Overall, our results showed that the perfect-flowered cultivars ‘Hall’ and ‘Paulk’ combined highly desirable traits such as high productivity with large sized berries with excellent firmness, and relatively low percent berries with wet stem scar. ‘Razzmatazz’ was characterized by small clusters of berries with high soluble solids, high titratable acidity, low pH, and a low TSS:TA ratio. Three of the advanced perfect-flowered selections planted in 2021 were released as commercially available cultivars during the study duration, namely: selection AM-70 was released as ‘Mighty FineTM’, AM-77 was released as ‘AltusTM’, and selection Ga. 6-1-269 was released as ‘Gold DelightTM’. Among the advanced selections, yield per vine differed by genotype and year, but was not affected by genotype × year interaction. ‘Gold Delight™’, Ga. 13-4-2, and AM-195 produced yields comparable to the standard ‘RubyCrisp®’. Individual berry weight differed by genotype and year. ‘Gold Delight™’ vines consistently produced the largest berries followed by ‘Mighty Fine™’, both showing excellent fresh market trait. A genotype × year interaction was accountable for the percent berries with wet stem scar and the total soluble solids content of the advanced selections. AM-26 had the lowest percent berries with wet stem scar, whereas ‘Altus™’ had the highest percent berries with wet stem scar in 2025. Berry firmness and titratable acidity differed by genotype and year. ‘Altus™’ produced relatively smaller berries with low TSS and more acidic fruit than other genotypes, consistent with its release for processing cultivar rather than for the fresh-market use. Overall, ‘Gold Delight™’ and ‘Mighty Fine™’ demonstrated a combination of desirable fresh-market cultivar characteristics such as excellent productivity, large berry size and good sugar-to-acid balance.