Capturing the genetic diversity of wild relatives is crucial for improving crops because wild species are valuable sources of agronomic traits that are essential to enhance the sustainability and adaptability of domesticated cultivars. Genetic diversity across a genus can be captured in super-pangenomes, which provide a framework for interpreting genomic variations.

French-American hybrids and North American grape species play a significant role in Canada's grape and wine industry. Unfortunately, the occurrence of viruses and viral diseases among these locally important non- grapes remains understudied. We report here the results from a large-scale survey to assess the prevalence of 14 viruses among 533 composite samples representing 2665 vines from seven French-American hybrid wine grape cultivars, two North American juice grape cultivars (Concord and Niagara), and the table grape cultivar Sovereign coronation. Based on reverse transcription polymerase chain reaction (RT-PCR) assays, ten viruses were detected. Grapevine rupestris stem pitting-associated virus, grapevine leafroll-associated virus 3, grapevine Pinot gris virus and grapevine red blotch virus were detected with the highest frequency. As expected, mixed infections were common; 62% of the samples contained two or more viruses. Overall, hybrid wine grapes were infected with more viruses and a higher prevalence of individual viruses than juice and table grapes. To validate these findings and to refine the virome of these non-European grapes, high-throughput sequencing (HTS) analyses of five composite samples representing each category of grapevine cultivars was performed. Results from HTS agreed with those from RT-PCR. Importantly, Vidal, a widely grown white-wine grape with international recognition due to its use in the award-winning icewine, is host to 14 viruses, four of which comprise multiple and distinct genetic variants. This comprehensive survey represents the most extensive examination of viruses among French-American hybrids and North American grapes to date.

The muscadine ( syn. ) is an American grape species native to the southeastern United States that has been cultivated for centuries. Muscadines are one of three grape species in subgenus with a chromosome number of 2 = 40 (, , and ), making them genetically distinct from the European wine and table grape () and other species in subgenus . Crop improvement efforts have been continuous since the late 19th century, yet the germplasm that served as the foundation for early muscadine breeding efforts was sourced from a relatively small portion of their native range, mostly in the coastal plains of North Carolina. This study used the rhAmpSeq core panel haplotype markers to genotype 194 accessions from five cultivated populations and 15 wild populations collected across their native range. Wild populations from the western half of the native range were generally less genetically differentiated than hypothesized, but were genetically distinct from the material used in both past and present breeding efforts. One population collected from coastal North Carolina grouped closely with accessions despite being well outside the reported range for that species. Principal coordinate and analyses revealed three main groups within the 194 accessions: one for cultivated material, one for wild , and one for and . At  = 5, results showed that more recent muscadine cultivars are further differentiated from wild accessions and varieties. These analyses confirmed our hypothesis that muscadine cultivars are genetically differentiated from their wild counterparts. This study also showed that genetic diversity in is not equally distributed across its native range and that the limited number of genotypes used in crop improvement efforts has not fully utilized the genetic diversity within the species.

Grapevines ( spp.) host viruses belonging to 17 families. Virus-associated diseases are a constant challenge to grape production. Genetic resources for breeding virus-resistant grape cultivars are scarce. 'Norton' is a hybrid grape of North American and is resistant to powdery mildew and downy mildew. In this study, we assessed resistance of 'Norton' to grapevine vein clearing virus (GVCV), which is prevalent in native, wild Vitaceae and in vineyards in the Midwest region of the U.S. We did not detect GVCV in 'Norton' as either the scion or the rootstock up to 3 years after it was grafted with a GVCV-infected 'Chardonel' grapevine. Upon sequencing of small RNAs, we were able to assemble the GVCV genome from virus small RNAs in GVCV-infected 'Chardonel' scion or rootstock, but not from grafted 'Norton' scion and rootstock. This study unveils a new trait of 'Norton' that can be used in breeding GVCV-resistant grape cultivars, and to investigate genetic mechanisms of 'Norton' resistance to GVCV.

'Concord', the most well-known juice grape with a parentage of the North American grape species L., possesses a special 'foxy' aroma predominantly resulted from the accumulation of methyl anthranilate (MA) in berries. This aroma, however, is often perceived as an undesirable attribute by wine consumers and rarely noticeable in the common table and wine grape species . Here we discovered homology-induced promoter indels as a major genetic mechanism for species-specific regulation of a key 'foxy' aroma gene, anthraniloyl-CoA:methanol acyltransferase (), that is responsible for MA biosynthesis. We found the absence of a 426-bp and/or a 42-bp sequence in promoters highly associated with high levels of expression and MA accumulation in 'Concord' and other -derived grapes. These promoter variants, all with direct and inverted repeats, were further confirmed in more than 1,300 germplasm. Moreover, functional impact of these indels was validated in transgenic . Superimposed on the promoter regulation, large structural changes including exonic insertion of a retrotransposon were present at the locus in some grapes. Elucidation of the genetic regulation advances our understanding of the 'foxy' aroma trait and makes it genetically trackable and amenable in grapevine breeding.

The maternal and paternal parentage of 36 rootstocks was determined and verified. The results of this study indicate that existing grape rootstocks are closely related to each other and have a narrow genetic background. Rootstocks are used to protect grapevines from biotic and abiotic stresses including phylloxera, nematodes, viruses, limestone-based soils, salinity and drought. The most important rootstocks were developed from three grape species between the 1890s and the 1930s in European breeding programs. In this report, we developed nuclear and chloroplast SSR fingerprint data from rootstock selections maintained in germplasm collections, compared them to develop a reference dataset, and carried out parentage analysis to resolve previously reported, and determine new, breeding records. We refined and updated the parentage of 26 rootstocks based on 21 nuclear and 14 chloroplast markers. Results indicate that 39% of the genetic background of analyzed rootstocks originated from only three accessions of three grape species: Vitis berlandieri cv. Rességuier 2, V. rupestris cv. du Lot and V. riparia cv. Gloire de Montpellier. Results determined that Rességuier 2 is the maternal parent for 14 commercial rootstocks, 9 of which are full-sibs with Gloire de Montpellier as the paternal parent. Similarly, du Lot is the paternal parent of nine rootstocks. The pedigree information for 28 rootstocks was determined or corrected in this study. The previously reported pedigree information for eight of the rootstocks was correct. The results found that the world's existing rootstocks have a narrow genetic base derived from only a few American grape species. Future rootstock breeding efforts should use a more diverse array of species to combat a changing climate and pest pressure.

Few studies investigated the biological effects of American grape cultivars. We investigated the metabolic response after acute consumption of grape juice or wine from Bordo grapes () in a placebo-controlled crossover study with fifteen healthy volunteers. Blood samples were collected 1 hour after the intake of 100 mL of water, juice, or wine to measure TBARS, ABTS, FRAP, glucose, and uric acid levels. To evaluate differences in cellular response, intracellular reactive species production (DCFH-DA) and metabolic mitochondrial viability (MTT) were assessed after exposure of human neuron-like cells (SH-SY5Y) to juice or wine. Glycemia was reduced after juice or wine consumption, whereas blood levels of uric acid were reduced after juice consumption but increased after wine consumption. Juice and wine consumption reduced plasma lipid peroxidation and increased plasma antioxidant capacity (ABTS and FRAP assays). Furthermore, juice inhibited HO-induced intracellular production of reactive species (RS) and increased the viability of SH-SY5Y cells. In contrast, wine (dealcoholized) exhibited a per se effect by inducing the production of RS and reducing cell viability. These results indicate a positive impact of acute consumption of Bordo juice and wine on human oxidative status, whereas only juice had protective effects against oxidative stress-induced cytotoxicity.

Historically, Michigan's climate had mainly three challenges for grape production: growing season temperatures were too low, the growing season was too short and there was too much rain near harvest. However, climate change in the past decades has led to a vastly different landscape that is evolving to meet the new climate. Recently, there has been a significant move from Vitis labrusca (North American) grape plantings to Vitis vinifera (wine grapes) as a consequence of Michigan's shifting climate. The goal of this study was to analyze the historical shift in climate and its potential future impact on the grape industry. We obtained data climate model projection data from two greenhouse gas (GHG) emission scenarios. First, a multi-linear regression model was built to predict future grape yields (t/ac) using data from the climate model projections. Second, trends in the severity of the three challenges (temperature, season length, precipitation timing) were analyzed. In both GHG scenarios grape yields are seen to improve, but to different extents. The improvement is likely a response to warmer season temperatures canceling out losses to early season frost. Model projections recommend that Michigan's future climate will be more accommodating for all varieties of grapes. This suggests that grape production will continue to grow, but the landscape will continue to evolve with more emphasis on varieties that are more climatically sensitive to cold temperatures. Climate change has greatly affected Michigan's viticultural landscape, and will continue to do so in the coming decades.

While the potential of dietary phenolics to mitigate glycemic response has been proposed, the translation of these effects to phenolic rich foods such as 100% grape juice (GJ) remains unclear. Initial in vitro screening of GJ phenolic extracts from American grape varieties (V. labrusca; Niagara and Concord) suggested limited inhibitory capacity for amylase and α-glucosidase (6.2%-11.5% inhibition; p < 0.05). Separately, all GJ extracts (10-100 µM total phenolics) did reduce intestinal trans-epithelial transport of deuterated glucose (d7-glu) and fructose (d7-fru) by Caco-2 monolayers in a dose-dependent fashion, with 60 min d7-glu/d7-fru transport reduced 10%-38% by GJ extracts compared to control. To expand on these findings by assessing the ability of 100% GJ to modify starch digestion and glucose transport from a model starch-rich meal, 100% Niagara and Concord GJ samples were combined with a starch rich model meal (1:1 and 1:2 wt:wt) and glucose release and transport were assessed in a coupled in vitro digestion/Caco-2 cell model. Digestive release of glucose from the starch model meal was decreased when digested in the presence of GJs (5.9%-15% relative to sugar matched control). Furthermore, transport of d7-glu was reduced 10%-38% by digesta containing bioaccessible phenolics from Concord and Niagara GJ compared to control. These data suggest that phenolics present in 100% GJ may alter absorption of monosaccharides naturally present in 100% GJ and may potentially alter glycemic response if consumed with a starch rich meal.

Plants employ two layers of defence that differ with respect to cell death: pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). In our previous work, we have comparatively mapped the molecular events in a cell system derived from the wild American grape Vitis rupestris, where cell death-independent defence can be triggered by PAMP flg22, whereas the elicitor Harpin activates a cell death-related ETI-like response. Both defence responses overlapped with respect to early events, such as calcium influx, apoplastic alkalinisation, oxidative burst, mitogen-activated protein kinase (MAPK) signalling, activation of defence-related genes and accumulation of phytoalexins. However, timing and amplitude of early signals differed. In the current study, we address the role of jasmonates (JAs) as key signalling compounds in hypersensitive cell death. We find, in V. rupestris, that jasmonic acid and its bioactive conjugate jasmonoyl-isoleucine (JA-Ile) rapidly accumulate in response to flg22 but not in response to Harpin. However, Harpin can induce programmed cell death, whereas exogenous methyl jasmonate (MeJA) fails to do so, although both signals induce a similar response of defence genes. Also in a second cell line from V. vinifera cv. 'Pinot Noir', where Harpin cannot activate cell death and where flg22 fails to induce JA and JA-Ile, defence genes are activated in a similar manner. These findings indicate that the signal pathway culminating in cell death must act independently from the events culminating in the accumulation of toxic stilbenes.