Comparison of Salt Exclusion in Muscadine and Interspecific Hybrid Grapes Using a Greenhouse Screening Procedure

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.

Tolerance of Muscadine grapes (Vitis rotundifolia) to alkaline soil

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.

Molecular Characterization and Phylogenetic Analysis of MADS-Box Gene VroAGL11 Associated with Stenospermocarpic Seedlessness in Muscadine Grapes

Reduced expression of MADS-box gene AGAMOUS-LIKE11 (VviAGL11) is responsible for stenospermocarpic seedlessness in bunch grapes. This study is aimed to characterize the VviAGL11 orthologous gene (VroAGL11) in native muscadine grapes (Vitis rotundifolia) at the molecular level and analyze its divergence from other plants. The VroAGL11 transcripts were found in all muscadine cultivars tested and highly expressed in berries while barely detectable in leaves. RT-PCR and sequencing of predicted ORFs from diverse grape species showed that AGL11 transcripts were conservatively spliced. The encoded VroAGL11 protein contains highly conserved MADS-MEF2-like domain, MADS domain, K box, putative phosphorylation site and two sumoylation motifs. The muscadine VroAGL11 proteins are almost identical (99%) to that of seeded bunch cultivar, Chardonnay, except in one amino acid (A79G), but differs from mutant protein of seedless bunch grape, Sultanina, in two amino acids, R197L and T210A. Phylogenetic analysis showed that AGL11 gene of muscadine and other Vitis species formed a separate clade than that of other eudicots and monocots. Muscadine grape cultivar “Jane Bell” containing the highest percentage of seed content in berry (7.2% of berry weight) had the highest VroAGL11 expression, but almost none to nominal expression in seedless cultivars Fry Seedless (muscadine) and Reliance Seedless (bunch). These findings suggest that VroAGL11 gene controls the seed morphogenesis in muscadine grapes like in bunch grape and can be manipulated to induce stenospermocarpic seedlessness using gene editing technology.

The Muscadine Grape (Vitis rotundifolia Michx)

The muscadine grape is native to the southeastern United States and was the first native grape species to be cultivated in North America. The natural range of muscadine grapes extends from Delaware to central Florida and occurs in all states along the Gulf Coast to east Texas. It also extends northward along the Mississippi River to Missouri. Muscadine grapes will perform well throughout Florida, although performance is poor in calcareous soils or in soils with very poor drainage. Most scientists divide the Vitis genus into two subgenera: Euvitis (the European, Vitis vinifera L. grapes and the American bunch grapes, Vitis labrusca L.) and the Muscadania grapes (muscadine grapes). There are three species within the Muscadania subgenera (Vitis munsoniana, Vitis popenoei and Vitis rotundifolia). Euvitis and Muscadania have somatic chromosome numbers of 38 and 40, respectively. Vines do best in deep, fertile soils, and they can often be found in beside river beds. Wild muscadine grapes are functionally dioecious due to incomplete stamen formation in female vines and incomplete pistil formation in male vines. Male vines account for the majority of the wild muscadine grape population. Muscadine grapes are late in breaking bud in the spring and require 100-120 days to mature fruit. Typically, muscadine grapes in the wild bear dark fruit with usually 4 to 10 fruit per cluster. Bronze-fruited muscadine grapes are also found in the wild, and they are often referred to as scuppernongs. There are hundreds of named muscadine grape cultivars from improved selections, and in fact, one that has been found in the Scuppernong river of North Carolina has been named Scuppernong. There are over 100 improved cultivars of muscadine grapes that vary in size from 1/4 to 1 ½ inches in diameter and 4 to 15 grams in weight. Skin color ranges from light bronze to pink to purple to black. Flesh is clear and translucent for all muscadine grape berries. Originally published 1994 by Peter C. Anderson and Timothy E. Crocker. Published on EDIS June 2003. Revised November 2010, October 2013, January 2017. This revision with Sarkhosh and Huff.

Glutathione S-transferase: A Candidate Gene for Berry Color in Muscadine Grapes (Vitis rotundifolia)

Muscadine grapes (Vitis rotundifolia Michx.) are a specialty crop cultivated in the southern United States. Muscadines (2n=40) belong to the Muscadinia subgenus of Vitis, while all other cultivated grape species belong to the subgenus Euvitis (2n=38). The berry color locus in muscadines has been mapped to a 0.8 Mbp region syntenic with chromosome 4 of V. vinifera. In this study, we identified glutathione S-transferase4 (GST4) as a likely candidate gene for anthocyanin transport within the berry color locus. PCR and KASP genotyping identified a single intragenic SNP (C/T) marker corresponding to a proline to leucine mutation within the muscadine GST4 (VrGST4) that differentiated black (CC and CT) from bronze (TT) muscadines in 65 breeding selections, 14 cultivars, and 320 progeny from two mapping populations. Anthocyanin profiling on a subset of the progeny indicated a dominant VrGST4 action, with no allele dosage effect on total anthocyanin content or composition of individual anthocyanins. Proanthocyanidin content was similar in the seeds of both black and bronze genotypes, and seeds had much higher VrGST3 expression and lower VrGST4 expression than skins. VrGST4 expression was higher in post-veraison berries of black muscadines compared to pre-veraison berries, but no changes in gene expression in pre- and post-veraison berries were observed in the bronze muscadine cultivar. VrMybA1 expression was higher in post-veraison berries of both black and bronze muscadines. These results suggest that berry pigmentation in muscadines is regulated by a mechanism distinct from the MybA gene cluster that is responsible for berry color variation in V. vinifera.

Draft Genome Sequences of Xylella fastidiosa subsp. fastidiosa Strains OK3, VB11, and NOB1, Isolated from Bunch and Muscadine Grapes Grown in Southern Mississippi

ABSTRACT We report here high-quality draft whole-genome assemblies of Xylella fastidiosa subsp. fastidiosa strains OK3, VB11, and NOB1, which were isolated from symptomatic bunch and muscadine grape plants grown in southern Mississippi.

Chemical Composition, In Vitro Antioxidant Potential, and Antimicrobial Activities of Essential Oils and Hydrosols from Native American Muscadine Grapes

Essential oils and hydrosols of two cultivars of muscadine grapes (Muscadinia rotundifolia (Michx.) Small.) were obtained by hydro-distillation of flowers and berry skins. Twenty-three volatile compounds were identified in essential oils from the muscadine flowers, and twenty volatiles in their corresponding hydrosols. The composition of volatiles in berry skins differed significantly from that of the vine flowers. The antioxidant potential of investigated essential oils and hydrosols was evaluated using five in vitro assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) method, TEAC (Trolox equivalent antioxidant capacity), FRAP (Ferric reducing antioxidant power), CUPRAC (cupric ion reducing antioxidant capacity), and NO (nitric oxide radical scavenging assay). The essential oils from the flowers of both cultivars showed the strongest antioxidant power, whereas the hydrosols were the significantly less active. All investigated essential oils showed very weak antibacterial activities against Bacillus cereus, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. However, the essential oils from the flowers of both cultivars showed moderate antifungal activities against Candida albicans, which were stronger for the oil from “Carlos” (white muscadine cultivar). To the best of our knowledge, this is the first report on obtaining and characterizing essential oils and hydrosols from muscadine grapes. This study demonstrated the variations in aromatic compounds accumulated in flowers and mature berry skins of muscadine grapes, and evaluated their possible antioxidant and antimicrobial activities. The presented results will be the base for future research, focused on a better understanding of the molecular and regulatory mechanisms involved in aromatic compound biosynthesis and accumulation in muscadine grapes.