1. Introduction
The Nova Scotia (Canada) wine industry was born in the 1980s and is relatively young compared to the rest of the winegrowing regions of the New World [
1]. According to the economic impact report of 2015, the wine industry contributes to Nova Scotia’s economy with a business revenue of
$154 million, tax revenue of
$27.6 million and wages of nearly
$37 million. The overall economic impact was
$218 million in 2015, which showed an increase of over
$22 million since 2011 [
2].
The best sites for viticulture in Nova Scotia are those located in areas where the typical winter minimum temperature is above −23 °C and the growing season is above 900 growing degree days [
3]. Nova Scotia’s wine industry is greatly based on the production of cold-hardy interspecific hybrid grape (CIHG) varieties, such as L’Acadie, Maréchal Foch, New York Muscat, Seyval, Léon Millot, Lucy Kuhlman, Baco Noir, and Vidal.
Vitis vinifera varieties such as Chardonnay, Riesling, Pinot Noir and Sauvignon Blanc are less cultivated; however, they are becoming more popular [
4,
5].
CIHG varieties are obtained from the crosses between
V.
vinifera and North American native
Vitis species, such as
V.
labrusca and
V.
riparia [
6,
7]. These hybrids have contributed widely to the expansion of Northern viticultural areas which are characterized by extremely cold winters, short growing seasons, and high fungal disease pressure [
8]. Under these conditions, CIHG may provide a high tolerance to cold winters, spring frosts, cryptogamic diseases and having a short growing season [
8]. These hybrids are commonly used to produce rosé, red, white, sparkling, port-style and ice wines [
7,
9,
10,
11]. L’Acadie is a flexible variety used for still and sparkling wine production, while New York Muscat is used in blends for still and sparkling wines [
1]. Pinot Noir and Chardonnay are used for both still and sparkling wine production. Riesling is used mainly for still wine and occasionally for sparkling and ice wine [
9].
Local experience confirms that CIHG varieties are proven performers in Nova Scotia; nevertheless, the production of V. vinifera grapevine varieties should be reserved for exceptional sites and experienced growers. However, to our knowledge, there are no published reports in the scientific literature that demonstrate this hypothesis. In addition, this was part of the first Terroir study developed in Atlantic Canada according to our knowledge. Therefore, the aim of this study was to evaluate the viticultural behavior of two CIHG varieties, L’Acadie and New York Muscat, and three V. vinifera varieties, Chardonnay, Riesling and Pinot Noir cultivated in Annapolis Valley over three consecutive seasons.
4. Discussion
Based on bioclimatic indices, season affected grapevine phenology of cold-hardy interspecific hybrid grapes (CIHG) and
Vitis vinifera grapevine varieties (
Table 3). In this fashion, hybrids and
V.
vinifera varieties differentially behaved if extreme climate conditions in a season were present. As expected, the dates of budburst, bloom, véraison and harvest were delayed in the coldest season and presented the lowest heat accumulation in terms of Winkler Index (WI), Heliothermal Index (HI), Growing Season Temperature (GST) and chilling hours (
Supplementary Figure S1). However, it is interesting to note that the coldest season presented the shortest budburst to bloom interval and the longest bloom to véraison duration (
Table 3). The ripeness cycle is critical in wine production, offering specific characteristics in relation to their origin [
26]. Grapes ripen too late in the season in Annapolis Valley and may not reach full ripeness, usually resulting in wines with high levels of acidity and green flavors. Soil temperature has a significant effect on vine phenology [
26]. In this fashion, following winter dormancy, a high sum of cumulative heat units absorbed by the soil stimulated root starch and N mobilization and root growth and primary nutrient uptake, with further consequences on canopy growth and altered N partitioning among the plant components [
27].
Our results confirmed the difficulty of bringing the harvest to optimal maturity during the coldest season, showing that this area of Nova Scotia is at the edge of the wine production zone [
28], and that low-quality vintages must be accepted from time to time. This confirms that the potential for wine in this area is based on cold climate varieties, such as Riesling, Chardonnay, and Pinot Noir, and some CIHG varieties, especially L’Acadie. The latter variety showed the earliest budburst and presented a short ripening cycle (
Table 3). Based on previous research, this variety is well distinguished by its winter hardiness (−31 °C), consistent short growing season, and low heat unit condition close to 964 heat units higher than 10 °C [
29]. Recent local investigations have shown that the temperature at which 90% of the primary buds will be killed in L’Acadie is around −29 °C. The lineage of L’Acadie includes
Vitis vinifera (53.5%),
V.
rupestris (22.7%),
V.
aestivalis (8.8%),
V.
labrusca (8.6%),
V.
riparia (3.1%),
V.
cinerea (1.8%) and
V.
berlandieri (1.5%) [
29], which may determine its low chilling requirements and fast budburst compared to other varieties [
30].
Based on our results, the L’Acadie grapevine may present a higher tolerance to frost damage compared to New York Muscat, Chardonnay and Pinot Noir grapevines since only their secondary and tertiary buds were able to burst and to produce fruit in the 2018 season. The Riesling plot was not impacted with the same intensity compared to the other studied varieties and their shoots stayed with minimum damage. Dormancy and cold hardiness in Riesling is strongly influenced by photoperiod, temperature, and seasonal carbohydrate changes [
31,
32]. Ferguson et al. [
33] showed that Riesling presented the highest bud cold hardiness among the
V.
vinifera grapevines. It seems to be that due to their high resistance to cold, the L’Acadie and Riesling varieties could better adapt under the cold conditions of the Annapolis Valley. Spring frost damage probably conditioned bunch weight and yield per grapevine, and the weight of berries of the following season (
Table 5).
The studied CIHG and
V.
vinifera grapevines exhibited adequate levels in most of the nutrients analyzed in petioles except for N (
Table 4). Excessive levels of N in petioles were found in
V.
vinifera varieties, while NY Muscat reached deficient levels of N (
Table 4). N absorption considerably affects shoot development [
34]. High N availability, soil moisture, precipitation and low-light conditions stimulated shoot growth and leaf area expansion and delayed leaf senescence [
35]. This relationship could be confirmed regarding
Figure 1 since CIHG, in addition to presenting low levels of nitrogen in the petioles, also presented a lower shoot growth than
V.
vinifera grapevines. L’Acadie was the only variety that presented adequate levels of N in the petioles. These results are contradictory since it is well known that the hybrids cultivated in Nova Scotia are characterized by their high vigor. Thereby, CIHG vines quickly form their canopy, and their growth stops early in the season, unlike the
V.
vinifera varieties that continue to develop. Based on our data, water status measurement reflected no water deficit of the grapevines measured (
Table 5). In addition, these results were confirmed through the δ
13C analysis that showed that none of the plots underwent water stress during the whole growing season (
Table 5). These findings meant that there was not sufficient water stress to permit grapevines to reduce vigor, in order to finish the shoot growing phase before harvest and, consequently, to improve the ripening process and wine grape quality, especially for red
V.
vinifera varieties. In addition,
V.
vinifera varieties were grafted onto 3309 Couderc rootstock due to their susceptibility to cold injury, while the CIHG were not grafted due to their inherent tolerance to these cold conditions (
Table 1). The 3309 C rootstock promotes low to medium vigor to scion, but it induces medium to high accumulation levels of N to the plant tissues [
36]. Therefore, cover crop floor management strategies, and organic or industrial waste selection should be used as sources of nutrients or soil conditioners for vineyards in the cool humid climate of Eastern Canada [
37]. In addition, the importance of both clone and rootstock selection in cool climate regions where freeze injury may occur also have been proposed by some authors [
38].
New York Muscat presented low B petiole levels and produced the weightiest berries, which was negatively correlated to Ca and Mg petiole content (
Supplementary Material). Ca deficiency is detrimental to fertilization and fruit set due to its importance for pollen tube growth. Generally, the soils of the selected vineyards in this trial are sandy soils, which display a low quantity of coarse elements, important levels of organic matter, a low to high soil acidity, a generalized potassium deficiency and a medium to high soil compaction in many soil profiles [
12]. In some areas of Nova Scotia, the local and most economical source of agricultural lime is from a dolomitic limestone quarry, but as a result, repeated applications of dolomitic lime can cause a build-up of soil Mg level. In this fashion, excessive Mg can lead to poor soil structure and may induce K and sometimes P deficiency, especially toward the end of the growing season. High Ca availability in soils may induce Mg deficiency due to competition among these cations for root uptake [
39]. This competence can be a more pronounced problem in the
V.
vinifera varieties established in Nova Scotia since the grapevines grafted on rootstocks derived from American
Vitis species may be more prone than own-rooted
V.
vinifera cultivars to such interference of high soil K with Mg uptake [
40]. Since Mg is more mobile in the phloem than Ca, Mg deficiency symptoms first become apparent as chlorotic discoloration in the interveinal areas of old leaves as chlorophylls are being dismantled. New York Muscat is a moderately vigorous variety and produces medium-sized and loosely filled clusters, which may be associated with B deficiencies or the genetics of the variety. Reducing N uptake in B-deficient grapevines leads to low leaf N status, sugar, and starch accumulation in the leaves, which can affect the reserve accumulation of the grapevine. This is of utmost importance in grapevines grown in cold climates, especially in CIHG which, according to our study, accumulate a lower content of petiolar B (
Table 5). Chardonnay presented the highest bunch weight, which was positively correlated to must yeast assimilable nitrogen (YAN) content. Different authors showed that nitrogen fertilization significantly increased bunch weight [
41,
42]. Low N availability in grapevines may result in reduced bunch numbers [
43,
44], while N addition to N-starved grapevines increased the number of seeds and berries and improved fruit set in grapevines [
45].
Season considerably influences physico-chemical parameters of musts at harvest (
Table 6). The coldest season led to a lower soluble solids content, while the warmest season induced the lowest acidity, malic acid, YAN, mineral N, and organic N content in the musts (
Table 6). At similar soluble solids levels in harvest, CIHG musts presented lower malic acid content than the musts obtained from the
V.
vinifera grapevine varieties (
Table 6). The introduction of CIHG adapted to cold climate conditions has allowed the development of the wine industry in Nova Scotia. However, the intrinsic acidity levels in fruits needs to be considered to produce quality wines in cool climates [
46,
47,
48,
49]. While malic acid content declines steadily after véraison, tartaric acid level is reduced at a much slower rate since it is not used in respiration, nor affected by the growing season’s temperature [
46,
50]. Despite this, the total acidity of the musts tended to be higher in the studied
V.
vinifera grapevine varieties compared to the CIHG (
Table 6).
In general, the musts from
V.
vinifera varieties presented higher YAN, mineral and organic N than the musts from CIHG (
Table 6). Methyl anthranilate, furaneol (2,5-dimethyl-4-hydroxy-2,3-dihydro-3-furanone), and o-aminoacetophenone, mostly called “foxy” compounds were identified as important contributors to wine aroma in different CIHG [
51,
52]. More recent studies showed that CIHG cultivated in Québec (Canada) presented high levels of C6 and other fatty acid degradation products, while nonanal, (E,Z)-2,6-nonadienal,
β-damascenone, ethyl octanoate and isoamyl acetate showed the highest odor activity values (OAVs) in the wines made from these varieties [
7,
53]. Some fermentative volatile compounds are produced from the yeast amino acid metabolism in cells and their concentration depends on the YAN content of the must [
54]. Higher alcohol content presents an initial increase at low YAN concentration and tends to decrease after a YAN concentration higher than 200–300 mg N L
−1 [
55]. Ethyl esters production as well as acetate esters, including ethyl acetates that contribute to fruity and floral wine aroma, is generally increased when YAN is up higher than 300 mg N L
−1 [
55].
5. Conclusions
Viticultural behavior of L’Acadie, New York Muscat, Chardonnay, Riesling, and Pinot Noir cultivated in Annapolis Valley were evaluated over three consecutive seasons. L’Acadie presented the earliest bud burst, bloom and véraison compared to the other studied grapevines, which provides key data for vineyard management decisions, such as frost management. In terms of nutrient uptake, L’Acadie showed the highest Mg content and lower N content compared to Vitis vinifera varieties; the latter condition affects their growth and decreases the growth rate at the end of the growing season, creating more adaptability to the local conditions. Related to their behavior after frost, L’Acadie showed a good resilience by having a positive second bud burst and even producing a small yield. New York Muscat grapevines had the main phenological stages later compared to L’Acadie; their nutritional uptake based on petiole analysis had the lowest levels of N, Ca, Mg and B. New York Muscat shoot growth had similarities to L’Acadie, diminishing their rate at the end of the season. Although the yield per plant was not the highest, their berries were bigger compared to the other grapevines and the malic acid levels were the lowest compared to other studied varieties. Chardonnay plants had phenological stages later compared to L’Acadie, at petiole analysis their N was highest, and their shoot growth showed high vigor. Their yield per plant and the bunch weight were one of the highest of the studied vines. Riesling and Pinot Noir plants were latest at the phenological stages. Riesling plants had highest levels of K at petioles analysis and higher N levels compared to CIHG, but overall, the nutritional condition was more balanced. They had a continuous shoot growth. Their yield per plant was the highest in this study. Although they showed the lowest malic acid compared to other studied V. vinifera varieties, their total acidity was the highest of all the studied varieties. Pinot noir showed the lowest P level at petiolar analysis, while Ca and N were the highest. The shoot growth was similar to the other V. vinifera varieties, the bunch weight was the lowest between the grapevines and had the highest malic acid levels. Based on the exposed results, L’Acadie plants, due their growth pattern and resilience to frost, and Riesling, due the nutrient conditions and good yields, showed a good adaptation to the edaphoclimatic conditions of Nova Scotia. L’Acadie is a widely used grape variety in the region, producing wine in different styles and qualities. This study proved its adaptation to the local climatic conditions. Contrary to the bibliography, CIHG presented lower levels of malic acid and total acidity compared to V. vinifera varieties, while V. vinifera showed a high content of N compounds in musts. Related to water demands, no water stress was found in any of the varieties through this study, neither by stem water potential nor δ13C analysis. Finally, L’Acadie would be more adapted to cold terroirs and in flat plots, whereas V. vinifera varieties should be established in the warmer sites of the valley and in slope zones.