A 9-year orchard experiment was established to measure the performance of Rootpac®-R, Rootpac®-20, Rootpac®-40, and Rootpac®-70 rootstocks using Redhaven peach (Prunus persica var. persica) as the scion, compared with Bailey, the current industry standard. Tree survival after 5 years was only 38% on Rootpac®-40, and the remaining rootstocks showed little or no tree mortality. Tree vigour and canopy height and width were influenced by rootstock genotype beginning the year of planting in 2016. Based on trunk cross-sectional area, after 9 years of production, Rootpac®-70 produced the largest trees followed by Rootpac®-40 and Rootpac®-R. Bailey and Rootpac®-20 had the lowest tree vigour. By year nine, cumulative yields were greatest on Rootpac®-70, measuring 5% higher than Bailey; cumulative yields of Rootpac®-R, Rootpac®-20, and Rootpac®-40 were 91%, 89%, and 81% that of Bailey, respectively. Cumulative yield efficiency was significantly influenced by rootstock, with Bailey being the most yield efficient and Rootpac®-40 the least. Rootpac®-40 generally produced the largest fruit. Based on tree vigour, high mortality of Rootpac®-40, and high suckering on Rootpac®-40, all Rootpac rootstocks evaluated in this study seem to impart excessive vigour unsuitable for higher density systems and offer no obvious advantage over Bailey rootstock, the current commercial standard in Southern Ontario.

Excessive fruit set in European (Prunus domestica L.) and Japanese (Prunus salicina L.) plum trees necessitates thinning to optimize crop load, enhance fruit quality, and reduce manual hand thinning. This study evaluated the efficacy of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (1-ACC) as a chemical thinning agent for the European plum cultivar ’Vibrant’ and the Japanese plum cultivar ’Early Golden’. Treatments were applied at full bloom (FB) and at the fruitlet stage (8-10 mm diameter) using 1-ACC concentrations of 150, 300, and 450 mg·L⁻¹. Horticultural measurements included crop load, yield, fruit size distribution, fruit quality, phytotoxic effects, and crop value. Applications of 1-ACC effectively reduced crop load, with FB applications producing greater thinning responses than fruitlet-stage applications. Increasing application rates resulted in decreased yield and crop value, while average fruit weight increased. No hand thinning was required in both years of the study due to poor pollination in the ’Early Golden’ orchard and atypical fruit drop unrelated to 1-ACC treatments following early fruit development in the ’Vibrant’ orchard; therefore, commercial thinning was not required. Thinning responses varied by cultivar and application timing, underscoring the importance of cultivar-specific thinning strategies. Ethylene evolution following 1-ACC application supported its role in fruit abscission, with ethylene peaks observed within 24 h and differing in intensity by application timing. These results indicate that 1-ACC is a viable chemical thinning agent for plums, although optimization of application timing and concentration, particularly in seasons with heavier fruit set, is required to balance thinning efficacy with economic returns.

Early crop load management of apple trees (Malus domestica Borkh.) is important to enhance fruit quality and reduce biennial bearing. Orchard experiments were conducted from 2020 to 2023 to evaluate the thinning efficacy of blossom sprays of 2.5% lime sulfur (LS) combined with 2% mineral oil, and 2% ammonium thiosulphate (ATS), each applied alone or in combination with post-bloom fruitlet thinning with 1500 mg & centerdot;L-1 carbaryl on Gala and Honeycrisp trees. Blossom applications were timed using the pollen tube growth model. Treatments were compared with untreated control trees and hand-thinned controls. Averaged over the 4 years and two cultivars, ATS and LS reduced fruit set by 9% and 29%, and crop load by 13% and 21%, respectively, relative to untreated controls. The carbaryl fruitlet treatment provided greater reductions in fruit set and crop load, but the integration of blossom and fruitlet thinner provided superior performance. In 1 year when natural crop loads were high, both blossom thinners significantly enhanced return bloom of Honeycrisp. Overall, blossom thinners provided only modest and inconsistent reductions in fruit set, but their use in sequential thinning programs may benefit biennial-prone cultivars by enhancing return bloom under heavy fruiting conditions. The benefits of early crop load reduction using LS and ATS blossom thinners need to be balanced with product costs, thinning efficacy, risk of natural thinning by frost, leaf phytotoxicity, and potential fruit russeting. Future research should focus on developing cost-effective blossom thinners with the aim of providing more consistent early reductions in crop load.

Crop load management of apple trees is necessary to improve fruit size, quality of apples and reduce biennial bearing. As an alternative to hand thinning, a new commercial thinning compound, 1-aminocyclopropane-carboxylic acid (ACC), has been in development for over a decade. A series of eight experiments were conducted to evaluate the efficacy of 1-aminocyclopropane- carboxylic acid (ACC) as a full bloom (FB) or post-bloom thinner for Ambrosia, Gala, Honeycrisp, and Crimson Crisp apple trees. Trees were treated with ACC at rates from 200-400 mg.L-1; different timings from FB to 20 mm; single, combination or sequential sprays of ACC with 6-benzyl adenine (6-BA) or 1-naphthaleneacetic acid (NAA); and two ACC formulations. Treatments were compared with untreated trees, hand thinned control (HTC), and grower control sprays of carbaryl, NAA, 6-BA, or combinations thereof. In all studies, single applications of ACC up to 400 mg.L-1 for fruitlet sprays and 600 mg.L-1 for full-bloom sprays failed to reduce fruit set or crop load compared to untreated trees. However, regression analyses indicated a significant linear or quadratic reduction in fruit set and crop load with increasing rates of ACC applied post-bloom in three of the six experiments. Ethylene emission peaked in fruits 1d after ACC was applied at 8-10 mm but was not detected when applied after 15-20 mm. Trees treated with carbaryl control sprays had comparable crop loads as the HTC and effective as a fruitlet thinner, but not in all experiments. ACC was not a sufficient substitute for carbaryl when used alone or tank mixed with 6-BA or used as a sequential spray. Further studies evaluating higher rates of ACC, using ACC in combination or sequence with other thinning agents, as well as understanding the reasons for its inconsistent thinning response are warranted.

Apple replant disease (ARD) can increase apple tree (Malus domestica Borkh) mortality, delay production, and reduce yield, resulting in losses of up to $60 K/ha over an orchard's lifespan. Common fumigation treatments can harm human and environmental health, have variable effectiveness, and disrupt beneficial soil microbial activity and processes. An experiment was conducted at the Simcoe Research Station in Norfolk County, Ontario to assess the effectiveness of commercially available plant growth-promoting (PGP) microbial biocontrols to treat ARD. Five treatments were replicated in-field five times as a randomized block design. Treatments included: untreated control, fumigation control (chloropicrin (FC)), PGP fungi (PGP-F), PGP rhizobacteria (PGP-R), and a combination of PGP-F and PGP-R (PGP-M). Trees growth and health and rhizosphere microbial diversity was assessed at three points over 2 years. PGP-R produced the greatest mean root mass followed by the chemical fumigation, which was 32% and 10% more root mass than the untreated control, respectively. Chemical fumigation resulted in the greatest above-ground biomass tree growth followed by the PGP-R, accumulating 30% and 6% more biomass than the untreated control. However, PGP-F accumulated less biomass than the untreated control. FC and PGP-R both resulted in strong growth but impacted the microbial community differently. PGP-R increased rhizosphere bacterial diversity and decreased fungal diversity while FC did the opposite. PGP-R changes to bacterial communities persisted while FC soils resembled the untreated control most closely after two years. These results indicate PGP-R biocontrol treatments are viable alternatives to fumigation for apple growers facing ARD.

Fruit quality attributes such as colour, firmness, crispness, juiciness and flavour are the primary factors that drive consumers choice when purchasing apples. Many of these characteristics are inherent with the genetics of the cultivar. However, several pre-harvest factors can be managed horticulturally by manipulating various aspects in the orchard, such as the tree canopy, or altering tree nutrition and irrigation management. Specific fruit quality attributes can be either improved by the application of plant bioregulators to minimize losses at harvest, but also are strongly influenced by environmental conditions in the orchard, especially light and temperature. This chapter will explore how pre-harvest management in the orchard can be optimized to improve fruit size, colour, and shape, and minimize defects caused by cracking or russet. Future innovations will also be discussed in the context of fruit quality and orchard sustainability.

The agricultural domain has been experiencing extensive automation interest over the past decade. The established process for measuring physiological and morphological traits (phenotypes) of crops is labour-intensive and error-prone. In this paper, a mobile robotic platform, namely The Autonomous Robot for Orchard Surveying (AROS), was developed to automate the process of collecting spatial and visual data autonomously. Furthermore, six different control frameworks are presented to evaluate the feasibility of using a kinematic model in agricultural environments. The kinematic model does not consider wheel slippage or any forces associated with dynamic motion. Thus, the following six controllers are evaluated: Proportional-Derivative (PD) controller, Sliding Mode Controller (SMC), Control-Lyapunov Function (CLF), Nonlinear Model Predictive Controller (NMPC), Tube-Based Nonlinear Model Predictive Controller (TBNMPC), and Model Predictive Sliding Mode Control (MPSMC). This paper provides insight into the degree of disturbance rejection that the mentioned control architectures can achieve in outdoor environments. Experimental results validate that all control architectures are capable of rejecting the present disturbances associated with unmodelled dynamics and wheel slip on soft ground conditions. Additionally, the optimal-based controllers managed to perform better than the non-optimal controllers. Performance improvements of the TBNMPC of up to 209.72% are realized when compared to non-optimal methods. Results also show that the non-optimal controllers had low performance due to the underactuated constraint present in the kinematic model.

This study evaluated the performance of 'Aztec Fuji (R)' grafted onto 14 rootstock genotypes and trained to a tall spindle orchard system. Herein we provide results of the 2014 NC 40 coordinated 'Fuji' trial, established at seven locations in the United States and Canada, eight years after initiation. The rootstocks tested were Budagovsky10 (B.10); the Cornell-Geneva rootstocks G.11, G.202, G.214, G.30, G.41, G.935, and G.969; and the Vineland rootstocks V.1, V.5, V.6, and V.7. The industry standard Malling rootstocks M.26 EMLA and M.9-T337 were included for comparison. Tree mortality, trunk cross-sectional area (TCA), tree canopy size, amount of rootstock suckering, yield, and number of fruits were recorded annually. All response variables were influenced by location and rootstock and the interaction of these two factors. By year eight, trees could be distinguished into three rather distinct rootstock vigor classes, as measured by TCA of the rootstock means pooled across all locations: those similar to M.9-T337 (G.935, B.10, G.214, G.11, G.41); those similar to M.26 EMLA (G.969, G.30, V.1); and those more vigorous than M.26 EMLA (V.7, V.5, V.6). Overall, G.935 was 6% smaller in TCA than M.9-T337, B.10, G.214, and G.41 were similar in size to M.9-T337, while G.11 was 3% larger than M.9-T337. G.969 and G.30 were 9% and 11% larger in TCA than M.26 EMLA, respectively, while V.1, V.7, V.5, and V.6 were 12%, 27%, 36%, and 39% larger, respectively than M.26 EMLA. Cumulative yield was not closely associated with tree vigor. All rootstocks out performed M.26 EMLA and M.9-T337 except B.10 and G.41. Averaged over all locations, cumulative yield efficiency (CYE) was greatest for G.935 and G.214. Tree mortality was highest on B.10 and M.9- T337, while suckering was high on M.9-T337, G.30, and G.935, as well as the Vineland rootstocks at some locations. As tree vigor, yield and yield efficiency are related to each scion and rootstock combination, it is necessary to evaluate these characteristics across multiple regions and management practices to identify which rootstocks perform consistently. These results will allow apple producers to make more informed decisions concerning rootstock selection for the tall spindle or similar orchard training systems based upon planting locations with similar growing conditions.

There is increasing interest in growing apple cultivars ( Malus domestica Borkh.) of European origin for the production of hard cider in Canada; however, little is known about their susceptibility to fire blight (FB). FB can spread rapidly through apple (and pear) orchards causing extensive tree mortality and economic loss. Twenty-eight promising cider cultivars were evaluated over a 7 year period, and in their seventh year of production they were severely naturally infected by an Erwinia amylovora outbreak causing FB. Herein, we report the bloom and harvest dates and tree mortality that developed largely as secondary shoot blight in the summer of 2021. Overall, the cultivars could be classified according to relative susceptibility to FB, based on percentage tree mortality after 7 years: Enterprise (0%); GoldRush and Porter’s Perfection (<20%); Binet Rouge, Kingston Black, Cline Russet, Dabinett, Grimes Golden, Frequin Rouge, Crimson Crisp®, Cox Orange Pippin, and Muscadet De Dieppe (20%–40%); Calville Blanc d’Hiver, Bramley’s Seedling, Yarlington Mill, Michelin, Bulmers Norman, Stoke Red, Golden Russet, Breakwell, Esopus Spitzenberg (50%–90%); Brown Snout, Medaille d’Or, Michelin, Brown’s Apple, Sweet Alford, Tydeman Late, Ashmead’s Kernel, and Tolman (90%–100%). This study highlights the importance of selecting FB tolerant cider cultivars and following best management orchard practices to reduce the spread and prevent infection, which can be achieved by using FB-resistant rootstock, controlling rootstock suckers, FB prediction models, and limited use of antibiotics, biologicals, and careful nitrogen application to regulate tree vigor.

This paper presents the application of machine vision and learning techniques to detect and identify the number of flower clusters on apple trees leading to the ability to predict the potential yield of apples. A new field robot was designed and built to collect and build a dataset of 1500 images of apples trees. The trained model produced a cluster precision of 0.88 or 88% and a percentage error of 14% over 106 trees running the mobile vehicle on both sides of the trees. The detection model was predicting less than the actual amount but the fruit flower count is still significant in that it can give the researcher information on the estimated growth and production of each tree with respect to the actions applied to each fruit tree. A bias could be included to compensate for the average undercount. The resulting F1-Score of the object detection model was 80%, which is similar to other research methods ranging from an F1-Score of 77.3% to 84.1%. This paper helps lay the foundation for future application of machine vision and learning techniques within apple orchards or other fruit tree settings.

The NC-140 project evaluated rootstocks for 40+ years. Coordinated peach rootstock testing began in 1984, and 6 trials were implemented, with 5 completed. The first trial included 16 states. Nine rootstocks included 4 industry standards (Prunus persica seedlings), a plum hybrid, own-rooted, and 3 Prunus hybrids. Peach seedling rootstocks had the best survival and yields except for 'GF677'. The 1994 trial was planted in 18 states/provinces with 18 rootstocks. High yielding rootstocks included the standards Lovell and Guardian (R). Yields were affected by rootstock and location. Ranking of rootstock performance did not change between years 5 and 8. Trials planted in 2001 and 2002 at 17 sites included 15 clonally propagated Prunus spp. and hybrid rootstocks and the peach seedlings 'Lovell', 'Bailey' and 'Guardian (R)'. Both trials ended prematurely after 5 or 6 years due to virus concerns. These trials showed the potential of semi-dwarfing rootstocks in peach and the shortcomings of slow growth, poor anchorage, suckering, delayed incompatibility, small fruit size, and increased tree death in vegetative propagated rootstocks. The last completed trial in 2009 at 16 locations with 18 rootstocks included interspecific hybrids. Significant differences were observed among rootstocks and locations for most horticultural traits. Peach and peach hybrid rootstocks were the most vigorous and productive, while the Controller (TM) series and plum rootstocks were the most yield efficient. In the southeastern US, 'Guardian (R)' was the best rootstock due to its tolerance to bacterial canker. In the northeastern US, 'Controller (TM) 7 and 8' showed superior performance to the traditional peach rootstocks. The hybrid 'Krymsk (R) 86' had a superior performance on high pH soils. Overall, 53 rootstocks were evaluated. Peach seedling rootstocks were often better performers, but recent trials of non-seedling propagated cultivars have been promising, which has encouraged increased planting of clonal rootstocks for peach in North America.

Eight vigor-limiting, standard, and vigorous Prunus rootstocks budded with 'Cresthaven' peach were planted at 10 locations in North America (nine in US and one in Canada) in spring 2017. During the first three years of establishment, significant differences among rootstocks and sites were found for survival, root suckers, tree growth, yield, fruit size, and yield efficiency. Tree survival was high (>96%) in SC, PA, MI, AL, CO, and UT and low (<75%) in NY, NC, and GA. 'Rootpac (R) 40' had the lowest overall survival (72%), followed by 'Controller (TM) 7', 'Rootpac (R) 20', and 'MP-29'. Rootstock suckering was excessive on 'Rootpac (R) 20' with 'Lovell' a distant second. The largest trees were in AL, followed by NY, SC, and UT, while the smallest trees were in CO, a short growing season site with calcareous soils and high soil pH. Averaged across all sites, the largest trees were on 'Guardian (R)', followed by 'Lovell', 'Rootpac (R) 20' and 'Controller (TM) 6' (76, 72, and 60% of 'Guardian (R)', respectively), whereas smallest trees were on 'Rootpac (R) 40' and 'MP-29' (both 41% of 'Guardian (R)'). In 2019, the first year that trees were cropped, 90% bloom varied across sites by 77 days, whereas 10% maturation differed by 55 days. However, no differences in bloom or harvest date were observed across rootstocks. Yield was highest in UT and AL (10-11 kg tree(-1)) and lowest in NC, CO, and GA (1-3 kg tree(-1)). The highest yields were on the most vigorous rootstocks 'Guardian (R)', 'Lovell', and 'Rootpac (R) 20', while lowest yield was on 'Rootpac (R) 40'. The rootstock with the highest yield efficiency was 'MP-29' while the lowest was 'Rootpac (R) 40'. Fruit size was large (227-298 g) in UT, SC, AL, moderate (195-213 g) in NC, PA, CO, and NY, and small (127 g) in GA. Averaged across sites, 'Controller (TM) 6' produced the largest fruits (249 g) while 'Guardian (R)' and 'MP-29' produced the smallest (210 g).

There is increasing interest in growing European origin apple cultivars for the production of hard cider in Canada; however, little is known about their winter hardiness. Eleven promising cider cultivars were evaluated for cold hardiness over two consecutive winters and compared with the winter tender cultivar ‘Golden Delicious’. Sections of the current season’s dormant shoots were frozen in a series of test temperatures ranging from −20 °C to −40 °C in a programmable freezer. Xylem tissue browning ratings were used to assess injury after thawing. The temperature of incipient damage (TID), the warmest temperature at which 1-yr-old shoot segments begin to show injury, was obtained from tissue browning curves using non-linear regression. TID varied significantly among cultivars and between sampling years. Overall, the cultivars could be classified according to relative winter hardiness as follows: Ashmead’s Kernel, Bramley’s Seedling (very tender) < Calville Blanc d’Hiver, Porter’s Perfection, Bulmer’s Norman (intermediate) < Crimson Crisp, GoldRush, Golden Delicious, Enterprise, Yarlington Mill, Enterprise (hardy) < Golden Russet (hardy). These data indicate nearly a 10 °C range in winter hardiness amongst the 11 cultivars studied, depending on the sampling date. Ashmead’s Kernel and Bramley’s Seedling appear to be particularly winter tender, whereas Bulmer’s Norman, Porter’s Perfection, and Calville Blanc d’Hiver demonstrated less hardiness during three of the four sampling dates. Based upon these findings, it would be prudent to consult long-term climate normals and consider the frequency of extreme weather events for potential susceptibility to winter injury, particularly prior to establishing more injury-prone cultivars.

Several experiments were conducted in Simcoe, Ontario, to evaluate the efficacy of metamitron (MET) as a post-bloom thinner for Ambrosia, Gala, and Honeycrisp apple trees. Trees were treated with rates of MET ranging from 165–480 mg·L −1 , as well as different timings ranging from 5–22 mm fruit diameter. The effect of including a non-ionic surfactant on thinning efficacy with MET was also evaluated. Treatments were compared with untreated trees and industry standard sprays of carbaryl, 1-naphthalene acetic acid (NAA), 6-benzyladenine (6-BA), or combinations thereof. Response to MET varied by cultivar and season. In six of the seven experiments MET reduced fruit set, but only in four experiments did MET reduce the number of fruit per tree or crop load compared with the untreated control trees. Petal fall (5–7 mm) applications of MET were less effective than later timings. Thinning response increased with higher rates of MET in four of the seven studies. For Honeycrisp and Ambrosia, 175 mg·L −1 MET was effective in reducing fruit set and crop load, while rates at or above 263 mg·L −1 MET were required to thin Gala. MET improved fruit size distribution into larger categories and caused minimal leaf phytotoxicity with or without a non-ionic surfactant. Environmental factors such as nighttime temperature and solar radiation largely could not account for the seasonal or application timings in thinning response to MET. Greater understanding of the carbon balance and interplay of solar radiation, nighttime temperature, cultivar and fruitlet size on thinning response is required to improve the predictive thinning response of apple to MET.

In 2014, a multi-year orchard experiment of apple Malus domestica (Borkh) was established at 14 locations in Canada, Mexico, and the United States using 'Honeycrisp' as the scion. Seventeen dwarf and semi-dwarf rootstock genotypes were tested, specifically: Budagovsky.10 (B.10), the Cornell-Geneva rootstocks G.11, G.202, G.214, G.30, G.41, G.890, G.935, G.969, the Malling rootstocks M.7, MM.106, and the Vineland rootstocks V.1, V.5, V.6, and V.7. The industry standard Malling rootstocks M.26 EMLA and M.9-T337 were included for comparison purposes. Tree mortality, trunk cross-sectional area, tree canopy size, amount of rootstock suckering, yield, and fruit number were measured annually. All measured parameters were influenced by location and rootstock, and the interaction of these two factors was significant. Overall, after five years and averaged over all locations, G.11 and G.41 were 6% smaller and 5% larger, respectively, than M.9-T337. G.935 and B.10 were 9% and 5% smaller, respectively, than M.26 EMLA, whereas G.214 and G.969 were 3% and 10% larger, respectively. V.1 and G.30 were 52% and 60% larger, respectively, than M.26 EMLA, whereas V.7, G.890, V.6, and V.5 were the largest genotypes in the trial, ranging from 77-95% larger than M.26 EMLA. G.202 performance was unusual and therefore was omitted from data analysis. Generally, cumulative yields per tree were greater on trees with the highest vigor. On average, 10 of the 16 rootstocks produced higher yields than M.9-T337 and M.26 EMLA; the newer rootstocks B.10, V.5, V.6, V.7 and all of the Geneva series rootstocks, with the exception of G.41, had cumulative yields that exceeded M.9-T337 and M.26 EMLA. Averaged over all locations, cumulative yield efficiency was greatest for G.935, G.214, M.9-T337, G.11, G.890, and G.969. Overall, the strong rootstock by location interaction on cumulative yield observed in this trial illustrates the importance of testing rootstocks at a regional level. These results are only reflective of the orchard establishment years; additional research must be completed before apple producers can make more informed decisions concerning rootstock selection for their orchard training systems and planting locations.

Insufficient biologically available nitrogen (N) for yeast is a persistent issue facing cidermakers, whose apple juice base usually does not provide adequate nutrition for a complete fermentation. Cidermakers often supplement their juice with additional yeast assimilable nitrogen (YAN) in the cellar to aid fermentation. The development of biologically available N in apple juice is not well understood. In this study, juice samples from ‘Crimson Crisp®’ apples were taken at several sampling dates in the 2016, 2017, and 2018 growing seasons and analyzed for YAN using formol titration and high-performance liquid chromatography. It was observed that while the total YAN concentration in these apples drops from the period shortly after fruit set to the end of summer, YAN remains stable from several weeks before harvest until the date of harvest. The total YAN did not change after a 6-week postharvest storage period. By contrast, the individual amino acid components of YAN do change during this period. This experiment shows that foliar urea sprays in ‘Crimson Crisp®’ produce an increase in organic N in the juice, mostly in the form of asparagine. Increased organic N impacts yeast growth and sensory characteristics of cider and may be seen as desirable by cider producers.

Twenty-eight apple cultivars were selected for their potential for hard cider production in Ontario; their juice characteristics were measured in 2017 and 2018, beginning two years after planting in 2015. After being harvested and pressed, each juice sample underwent analyses to determine soluble solids concentration (SSC), titratable acidity (TA), pH, yeast assimilable nitrogen (YAN), and polyphenolic concentration. Soluble solids concentration ranged from 10.6 °Brix in Brown’s Apple to 18.3 °Brix in Ashmead’s Kernel. Titratable acidity ranged from 31 as mg malic acid per 100 mL juice in Sweet Alford to 191 as mg malic acid per 100 mL juice in Bramley’s Seedling. The pH ranged from 2.88 in Breakwell to 4.76 in Sweet Alford. Yeast assimilable nitrogen concentration ranged from 60 mg YAN·L−1juice in Medaille d’Or to 256 mg YAN·L−1juice in Bulmer’s Norman. Polyphenols in juice ranged from 131 μg gallic acid equivalents (gae)·mL−1juice in Tolman Sweet to 1042 μg gae·mL−1juice in Stoke Red. Firmness ranged from 6.3 kg in Yarlington Mill to 11.7 kg in GoldRush. The relationships between these variables were also analyzed, showing a connection between acidity and juicing efficiency as well as a relationship between polyphenol concentration and fruit weight. Exploratory analyses indicated that juice attributes can be used to distinguish between cultivars and their origins. Cider producers can use these data to determine what to expect in juice from these cultivars.

A multi-year orchard experiment was established to measure the performance of Rootpac®-R, Rootpac®-20, Rootpac®-40, and Rootpac®-70 rootstocks using ‘Redhaven’ peach (Prunus persica var. persica) as the scion, compared with the ‘Bailey’ peach seedling rootstock, the current industry standard. Tree survival after five years was 79% on Rootpac-40, whereas the remaining rootstocks showed no tree mortality. Tree vigour and canopy height and width were influenced by rootstock genotype beginning the year of planting in 2016. For the first five years of production, Rootpac-70 consistently produced the largest trees based on truck cross-sectional area (TCSA) and by year five, all rootstocks produced trees with similar TCSAs, except for Rootpac-70, which was 38% larger than Bailey. By year five, cumulative yields were greatest on Rootpac-70, which were 10% higher than Bailey; cumulative yields of Rootpac-R, Rootpac-20, and Rootpac-30 were 98%, 89%, and 84% that of Bailey, respectively. Cumulative yield efficiency was significantly influenced by rootstock although the magnitude of the differences was small and likely of insignificant commercial importance. Rootpac-40 consistently produced the largest fruit. These results are only reflective of the orchard establishment years and additional data are required before peach producers can make fully informed decisions concerning the rootstocks evaluated in this study for their orchard systems. However, at this juncture, all the Rootpac rootstocks evaluated in this study are likely to impart excessive vigour to be used in a higher density system and offer little advantage over Bailey.

Continued interest in the commercial production of cider in Ontario has revealed that there is a lack of information available to apple producers and cidermakers on the juice attributes of culinary dessert apple for making cider and how they may vary from orchard to orchard. A two-year study was conducted to characterize the juice characteristics of 18 common culinary dessert apple cultivars grown at several locations in Ontario. Juice was assayed for soluble solids concentration, pH, titratable acidity (TA), juice extraction efficiency, yeast assimilable nitrogen (YAN), polyphenols, and soluble solids to TA ratio. Significant differences among cultivars were observed for all parameters, which varied by orchard and year, except juice extraction efficiency. These data underly the importance of assaying juice every growing season prior to fermentation. Cidermakers should focus on juice characteristics from culinary apples that are more difficult to alter (with amendments), and use juice with lower pH, higher TA and polyphenols, and moderate to higher YAN to optimize cider quality and flavour. Overall, this study will inform cidermakers of which culinary apple cultivars might be preferable for fermentation as well as how they might be blended to optimize cider quality. Notwithstanding annual and orchard variation, cultivars that meet these criteria include Cortland, Crimson Crisp, Honeycrisp, Jonagold, McIntosh, and Northern Spy. If making cider from Ambrosia, Crispin, Empire, Fuji, Gala, Golden Delicious, or Idared, cidermakers should expect to blend the juice from these cultivars to create a more fully balanced juice prior to fermentation.

The goal of this research was to evaluate resistance of apple rootstocks to late winter deacclimation during a 2-day exposure to warm temperatures in Maine. We measured the cold temperature tolerance of xylem, phloem, and cambium from 0 to −40 °C in 1- and 2-year-old shoot pieces from apple rootstock cultivars and advanced selections ‘M.9 T337’ (M.9), ‘M.7 EMLA’ (M.7), ‘Budagovsky 9’ (B.9), ‘Geneva® 41’ (G.41), ‘Geneva 30’ (G.30), ‘Geneva 935’ (G.935), ‘Geneva 814’ (G.814), G.4013, G.5257, and Vineland 6 (V.6) after a 2-day exposure to warm (22 °C) or cold (2 to 4 °C) temperatures. Injury was measured on a 0 to 10 rating scale based on percentage of discolored cross-sectional xylem and phloem, and cambial length and circumference with brown discoloration, with 0 indicating no browning and 10 indicating browning in the entire tissue. Injury was also measured as intensity of browning on a scale of 0 (no browning) to 5 (dark brown to black). The weighted averages of the two ratings were used to calculate an index of browning. Genotypic variation occurred in the degree of deacclimation, which ranged from none to as much as 15 °C loss in hardiness. Two genotypes, ‘G.41’ and ‘M.9’, showed little change in hardiness in both years they were tested. Two genotypes, G.4013 and ‘G.814’, lost substantial hardiness in both years and may be vulnerable to late winter freeze-thaw events, but were among the hardiest before deacclimation. ‘G.935’ and G.5257 showed a small loss of hardiness, whereas ‘B.9’ lost hardiness in the cambium, but not the xylem, and V.6 lost hardiness after warm exposure, but showed almost no injury at temperatures as cold as −35 °C. The loss of hardiness of these four genotypes that were tested in only one year should be verified with additional testing because of the potential for yearly variation.