THE IMPLEMENTATION OF HIGH-DENSITY PLANTING SYSTEMS TO MAXIMIZE THE YIELD AND QUALITY OF FRESH MARKET APPLES IN VIRGINIA

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1017819
• Project Start Date: Oct 1, 2018
• Project End Date: Sep 30, 2023
• Program Code: [(N/A)]- (N/A)

Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061

Performing Department
School of Plant and Environmental Sciences

Non Technical Summary
Summary and JustificationProblem Statement. To enhance their competitiveness in both national and international markets, commercial tree fruit growers must apply orchard management strategies that are economically and environmentally sustainable, meet consumer demand for high-quality fruit, and enhance production efficiency. One of the critical factors that impact orchard profitability is tree planting density. Planting densities can range from 100-300 trees/acre in low-density orchards to more than 1000 trees/acre in high-density systems. From an economic perspective, growers need to select planting systems that produce high yield of high-quality fruit, economize on labor inputs and allow trees to bear fruit as quickly as possible. Doing so will minimize the grower's period of negative cash flow and ensure a positive return on investment as quickly as possible. To realize economic benefits, high-density orchards require specific production principles and practices including the use of dwarfing rootstocks. Some of the benefits associated with planting higher-density orchards include the ability to produce high-quality fruit, greater pesticide application efficiency, and capacity to train, prune, and harvest from the ground. Transitioning to uniform, high-density orchards would also put growers in the best possible position from which they can take advantage of new labor-reducing technologies as they are developed. Over the last 15 years, it has become increasingly apparent that the fruit industry in Virginia is transitioning toward a higher proportion of fresh fruit production. Low prices in the processing market (e.g., unfermented juice, sauce, sliced fruit) have encouraged growers to re-focus their efforts on orchard systems based on fresh market apples and to adopt high-density planting systems. However, adopting high-density production systems in Virginia could be hampered by three major challenges: a) The high costs associated with establishing high-density training systems (e.g., vertical axis, tall spindle, super spindle) that require wires and posts for tree support; b) the high soil fertility and warm, humid growing season that increases tree vigor and, in turn, affects the spacing between trees and rows; and c) the lack of knowledge of how rootstocks and rootstock-scion combinations would affect fruit quality and tree sensitivity to physiological disorders (e.g., bitter pit). The overall goal of this project is to determine tree training systems, planting densities and apple rootstocks that achieve the maximum yield and quality of major fresh market apple varieties in Virginia; and to provide practical knowledge to apple growers and stakeholders that would enhance their profitability and competitiveness.Approach. To achieve this goal, the PI is planning to use the established field-blocks of mature apple trees in the AHS Jr. AREC's research farm, develop new on-farm demonstration and research plots, and conduct economic analyses to evaluate the effects of two training systems, eight planting densities, 19 rootstocks and 27 rootstock-scion combinations on the yield and quality of four fresh market apple varieties. The research findings of this project will be communicated to growers and stakeholders in VA through extension-oriented journals, web-based blogs, regional and state fruit grower meetings, as well as fruit schools and field days.Relevance to Virginia and the U.S. The United States is the world's second-largest exporter of fresh and processed apple products and, as such, apple represents an important crop for the nation from an economic perspective. Of the 50 states that grow apples, 36 do so for commercial purposes. Virginia is ranked 7th in the nation for apple production (VDACS, 2017). The state produces around 200 million pounds of apples annually, from 10,557 acres of land (NASS census, 2012). The production of apples for the fresh market has more than doubled in the last ten years, whereas the production for processing has decreased by 25% (NASS survey, 2017). Such transition in the marketing strategies has been demonstrated in a questionnaire used by the PI in 2017 to identify and set research priorities that reflect the interests of Virginia tree fruit growers and stakeholders. The majority of the respondents (total number =107) to this questionnaire were tree fruit growers representing 40 counties in Virginia. Other respondents were private agricultural consultants, agribusiness field representatives, and Extension educators. Most of the apple growers, making up 63% of respondents indicated that they are selling their fruit for fresh market (i.e. farm market, pick-your-own, wholesale to retailers). More than 80% of respondents ranked research topics that focus on the evaluation of apple rootstocks, strategies to reduce physiological fruit disorder, or strategies to improve fruit quality as "very important" or "important"; whereas less than 5% of the respondents rated these topics as "unimportant" or "not very important".Anticipated outcomes and impacts. This research project is expected to enhance the competitiveness of the Virginia's fresh market industry through increasing the yield and quality of fresh apples, increasing labor efficiency, adopting better orchard management practices, raising awareness of factors critical to orchard profitability and producing new knowledge of conditions affecting trees responses to physiological disorders. Outputs of this project may include but are not necessarily limited to, demonstration plantings for grower review, conference presentations, fact sheets, extension publications, various electronic media, and research journal articles. Outcomes would be anticipated to include increased grower adoption of higher density, more efficient orchard management practices and materials.

Animal Health Component

90%

Research Effort Categories

Basic

10%

Applied

90%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
203	1110	1020	100%

Knowledge Area
203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
1110 - Apple;

Field Of Science
1020 - Physiology;

Keywords

apple production

high-density planting

rootstock evaluation

fresh market

tree spacing

training systems

Goals / Objectives
Examine the effect of rootstocks and training systems on reducing the costs associated with establishing higher density apple orchards in Virginia. The three specific objectives related to this objective are:Evaluate the production efficiency of four dwarfing apple rootstocks (G.11, G.16, G.935 and G.890) in supported (i.e., tall spindle) versus non-supported (i.e., central leader) training systems.Examine the effect of different rootstocks on the yield and quality of three fresh market apple cultivars ('Fuji', 'Gala' and 'CrimsonCrisp').Estimate the economic costs and benefits of the examined rootstocks under different training systems and for the three apple cultivars.Examine planting densities that would achieve the highest yield efficiency and fruit quality under Virginia's soil condition.This research objective would specifically aim to:Determine planting spacing that would achieve the highest and most-consistent annual yield of 'Fuji' apples.Investigate the effect of different planting densities on fruit quality traits.Examine the effect of apple dwarfing rootstocks on the quality attributes of fresh market apples. The three specific aims to be investigated are:Evaluate 14 dwarfing and semi-dwarfing rootstocks for their effects on the quality traits of 'Honeycrisp' apples grown in a high-density production system.Examine the effect of 14 dwarfing and semi-dwarfing rootstocks on the nutrient content of 'Honeycrisp' apples as it relates to the occurrence of bitter pits.Provide educational materials and decision-making tools to apple growers and stakeholders in Virginia for adoption of high-density production systems

Project Methods
Methods/ProceduresObjective 1: Three scion varieties ('CrimsonCrisp', 'Aztec Fuji', 'Buckeye Gala') on four Geneva rootstocks (G.11, G.16, G.935 and G.890) will be planted in the AHS Jr. AREC research farm in April 2018. For each scion-rootstock combination, two training systems will be compared (tall spindle & central leader). The same scion trees grafted on Bud.9 will be planted in all plots as controls. Trees under each training system will be arranged in the field as a split-split plot design. Briefly, each of the three replicates will be divided into two sides, and training systems will be randomly assigned to each side. Each side then will be split into three sections and the three cultivars will be randomly assigned to each section. Each cultivar will be split into five sections, and for each, a rootstock will be randomly assigned. The rootstocks will be planted with a spacing of 7.5 X 13 ft (446 trees/acre) for the central leader, and 4 X 13 ft (837 trees/acre) for the tall spindle plots. For the free-standing central leader system, the trees will be trained into a Christmas tree shape, by keeping the top branches narrower than the lower ones. To control tree vigor, the central leader will be periodically headed back into the 2-year-old wood. For the tall spindle systems, trees will be supported by conduit posts and four wires spaced at 2, 5, 8 and 11 feet from the ground. Assessment of tree growth parameters will start from the first year of planting, whereas yield and fruit quality traits will be evaluated starting from the third year. Tree growth (e.g. trunk cross-sectional area (TCSA), number of suckers, terminal growth, branch number, tree survival), tree productivity (e.g. fruit number, yield, cumulative yield), and fruit quality traits (e.g. fruit weight, diameter, firmness, crispness, color, starch pattern index, soluble solids, titratable acidity, pH, dry matter) will be evaluated for all varieties, rootstocks and training systems every year according to the methods described previously (Kumar et al., 2012, Iglesias et al., 2008, Musacchi and Serra, 2018, Peck et al., 2006, Tatsuki et al., 2007).The economic feasibility of each of the training systems and rootstock-scion combination will be determined based on the establishment costs in the first year of planting (e.g. cost of trees, wires, posts, and labor), the maintenance costs (e.g. cost of fertilizers, fungicide and pesticide sprays and labor for fruit picking and pruning), and the cumulative yield ($/acre) of each system within a five-year period. The economic analysis of different variables will be performed in the last year of this project through collaboration with Prof. Darrell Bosch, Department of Agricultural and Applied Economics at Virginia Tech.Objective 2: Trees of 'Fuji' on M.9 rootstock were planted in 2012 in the AHS Jr. AREC, at Winchester in order to evaluate the effect of different planting densities on tree and crop characteristics under Virginia's soil conditions (Supplementary File 1). Trees were planted at 2, 3, 4, 5 and 6 feet between trees and 12 feet between rows to provide densities ranging between 605 to 1815 trees/acre. Trees are supported by a trellis system composed of five wires and conduit posts and are trained and pruned according to the tall-spindle training system, as previously described (Dominguez and Robinson, 2015). Trees for the five planting densities and three replicates (n=4 trees) are arranged in the field as a randomized complete block design (RCBD). This research trial was active for three years after planting but subsequently discontinued due to the moving of the former PI (Dr. Gregory Peck) to a different institute in 2015. Trees of this field trial have been well maintained during the last three years, but data collected from this experiment up to now is not sufficient to address the objectives of the current proposal, especially in regards to the effect of tree spacing on fruit quality, cumulative yield and yield efficiency. Evaluation of tree (e.g. TCSA, shoot length, leader length), crop (e.g. yield (kg/tree, kg/acre), yield efficiency (kg/cm2 TCSA), and cumulative crop value ($/acre) and fruit characteristics will be conducted as indicated above to advance this project.Objective 3. 'Honeycrisp' scions grafted on 14 dwarfing and semi-dwarfing rootstocks (B.10, G.11, G.202, G.214, G.30, G.41, G.935, G.969, M.26 EMLA, M.9 T337, V.1, V.5, V.6, V.7) were planted in a commercial orchard (Saunders Brothers Orchard, Piney River) in Central Virginia in 2014 as a part of an NC-140 project that encompasses nine states. The purpose of this multi-state project is to evaluate the effect of different rootstocks on the tree and crop characteristics (e.g. TCSA, number of rootsuckers, yield (kg/tree)) of 'Honeycrisp' trees grown under a high-density planting system (907 tree/acre), and trained in a tall-spindle training system. The PI is serving as a collaborator and the Virginia voting member in this project. The effect of these rootstocks on fruit quality and sensitivity to bitter pit has never been investigated in Virginia; hence, it will be examined as a part of the proposed Hatch project as additional effort beyond the scope of the NC-140 outlined project objectives. Trees are arranged in the field according to the completely randomized design (CRD) with ten single-tree replications. The fruit quality data will be collected from all rootstock-scion combinations as indicated above.For the assessment of rootstock effects on the development of bitter pit, 20 fruits from each tree will be sampled at harvest and will be split into two groups (one for at-harvest evaluation and one for after storage). For at-harvest evaluations, fruit will be left at room temperature for one week to acceleratebitterpitinduction that would have emerged in storage. We will thenmake an evaluation on whether or notbitterpitis present (binary) and the percentage of coverage. It is alsoimportant to factor in crop load and fruit size in these evaluations since both are co-dependent factors contributing to bitter pit development. Therefore, crop load will be measured for all trees based on the number of fruit/ cm2 of TCSA. Internalbitterpit will also be measured by slicing the apple into 1cm cross-sectional disks and counting the number of internalbitterpitlesions on the top side of each disk working from the calyx end upwards. For post-storage evaluation, if thebitterpitis going to develop, it will usually emerge within the first two months of storage at regular atmosphere (RA), so our storage times will include three months of storage in RA. After storage, we will do the same evaluation that we did at harvest except without the seven days at room temperature. Recent soil testing results have indicated that Ca and other nutrients are available in sufficient quantities and soil pH lies within the acceptable range. Samples will be collected from leaves and fruits at harvest for nutrient analysis, using the Agricultural Analytical Services Laboratory of Penn State University College of Agricultural Sciences.Statistical analysis.Completely randomized, randomized complete block, and split plot designs will be analyzed as appropriate using the ANOVA, GLM, or MIXED procedures of SAS statistical software (release 9; SAS Institute, Cary, NC, USA). The Tukey-Kramer HSD test will be used to compare means if necessary. The required assumptions, including constant variability by treatment and normality of residuals, will be checked and a transformation will be applied to the data if necessary.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:The target audience that was the focus of our efforts includes apple growers and stakeholders; pomologists and researchers; extension agents and specialists. Changes/Problems:PRogress on Objective 2 was not possible. No data were collected from this block in the 2020 season due to labor shortage as a result of Covid-19. b)Investigate the effect of different planting densities on fruit quality traits.No data were collected from this block in the 2020 season due to labor shortage as a result of Covid-19. What opportunities for training and professional development has the project provided?The PI provided instructions for measuring apples' physical and chemical quality parameters to a field specialist and two postdoctoral fellows at the AHS Jr. Agricultural Research and Extension Center, Winchester, VA. Training sessions focused mainly on the calibration and application of the fruit texture analyzer (FTA), DA meter, and refractometer to analyze fruit firmness, color and total solids, respectively in fruit samples from various treatments and research blocks. How have the results been disseminated to communities of interest?The PI presented the major findings of this proejctin five fruit schools in Southern, Central, and Northern Virginia (e.g., Winchester Regional Commercial Tree Fruit School, Rappahannock-Madison Area Fruit School, Central Virginia Commercial Tree Fruit Production School)during Feb 10-14, 2020. What do you plan to do during the next reporting period to accomplish the goals?My plans for the 2021 growing seasons are: a) Evaluate the effects of rootstocks and training systems on tree growth, tree survival and crop yield and quality of 'Gala,' 'Fuji' and 'Crimson Crisp' apples. b) Analyze the effects of tree spacing on 'Fuji' apple tree growth and fruit quality.c) Continue assessing the effects of dwarfing and semi-dwarfing rootstocks on fruit quality, nutrient content, and bitter pit incidence in 'Honeycrisp' apples. d) Disseminate research findings to tree fruit growers and stakeholders in Virginia through winter fruit schools, virtual meetings, and professional conferences.

Impacts
What was accomplished under these goals? Goal 1. The three specific objectives related to this objective are:a) Evaluate the production efficiency of four dwarfing apple rootstocks (G.11, G.16, G.935, and G.890) in supported (i.e., tall spindle) versus non-supported (i.e., central leader) training systems. To achieve this goal, three scion varieties ('Aztec Fuji', 'Buckeye Gala' and 'Crimson Crisp') on five dwarfing and semi-dwarfing rootstocks (B.9, G.11, G.935, G.890 and/or G.16) were planted in the AHS Jr. AREC's research farm on April 20, 2018. For each scion-rootstock combination, two tree support systems (trellis & free-standing) were compared. Trees under each system were arranged in three blocks (five trees/rootstock-scion combination/block) and distributed in the orchard according to the randomized complete block design (RCBD). The rootstocks were planted at a spacing of 7.5 x 12 ft (484 tree/acre) for the free-standing system, and 4 X 12 ft (906 tree/acre) for the trellis system. For the free-standing, the trees were trained to a central leader system. For the trellis systems, trees were supported by conduit posts and four wires spaced at 2, 5, 8 and 11 ft from the ground, and were trained to a tall spindle system. Evaluation of tree growth (e.g. trunk cross-sectional area (cm2), tree survival) were conducted for all rootstock-scion combinations and training systems at planting, and in falls of 2018-2020. Due to differences in tree spacing between the free-standing and trellis systems, statistical comparisons were only conducted among rootstocks and varieties under each system, but not between support systems. The 2020 TCSA (cm2) and yield (lb/tree) data can be summarized as follows: a) In all the tested scion varieties and regardless of the tree training system, trees grafted on G.890 were significantly the most vigorous, followed by G.935, G.11 and lastly Bud.9. b) Under the tall-spindle system, trees grafted on G.935 had the highest fruit yield (25.255 lb/tree), followed by G.890, Bud.9, and G.11. c) No significant effects were observed for the scion variety on tree vigor. As far as the yield is concerned, Crimson Crisp produced the lightest crop (232.4 bushels/acre), whereas Gala produced the highest crop (474.7 bushels/acre). d) compared with the trellis system, fruit yield was generally lower under the free-standing system, with significant differences observed among rootstocks and varieties. Crimson Crisp held the lowest yield (101 bushels/acre), whereases Gala had the highest yield (184 bushels/acre). e) Like the trellis system, G.890 produced the largest trees under the free-standing setup, followed by G.935, G.11, and Bud.9. However, no significant differences were observed in crop load between G.890 and G.935. Both rootstocks produced a relatively heavy crop (19.1 and 19.6 lb/tree, respectively). b) Examine the effect of different rootstocks on the yield and quality of three fresh market apple cultivars ('Fuji', 'Gala' and 'Crimson Crisp'). Effects of rootstocks on fruit yield (lb/tree & bushel/acre) were summarized above. Laboratory assessments of fruit quality attributes could not be completed 2020 seasondue to labor shortage at the harvest time. c) Estimate the economic costs and benefits of the examined rootstocks under different training systems and for the three apple cultivars. This goal is expected to be completed by the final year of this field trial (2023). Goal 2:This research objective specifically aims to: a) Determine planting spacing that would achieve the highest and most-consistent annual yield of 'Fuji' apples. To achieve this goal, trees of 'Fuji' on M.9 rootstock were planted in 2012 in the AHS Jr. AREC, at Winchester, to evaluate the effect of different planting densities on tree and crop characteristics under Virginia's soil conditions. Trees were planted at 2, 3, 4, 5 and 6 feet between trees and 12 feet between rows to provide densities ranging between 605 to 1815 trees/acre. Trees were supported by a trellis system composed of five wires and conduit posts and were trained and pruned according to the tall-spindle training system. This research trial was active for three years after planting but subsequently discontinued due to the moving of the former PI (Dr. Gregory Peck) to a different institute in 2015. Trees of this field trial have been well-maintained during the last four years, but data collected from this experiment up to now is not sufficient to address the objectives of the current proposal, especially in regards to the effects of tree spacing on fruit quality, cumulative yield and yield efficiency. No data were collected from this block in the 2020 season due to labor shortage as a result of Covid-19. b)Investigate the effect of different planting densities on fruit quality traits.No data were collected from this block in the 2020 season due to labor shortage as a result of Covid-19. Goal 3: The three specific aims to be investigatedunder this goal are:a) Evaluate 14 dwarfing and semi-dwarfing rootstocks for their effects on the quality traits of 'Honeycrisp' apples grown in a high-density production system. To achieve this goal, 'Honeycrisp' scions grafted on 14 dwarfing and semi-dwarfing rootstocks (B.10, G.11, G.202, G.214, G.30, G.41, G.935, G.969, M.26 EMLA, M.9 T337, V.1, V.5, V.6, V.7) were planted in a commercial orchard (Saunders Brothers Orchard, Piney River) in Central Virginia in 2014 as a part of an NC-140 project that encompasses nine states. The purpose of this multi-state project was to evaluate the effect of different rootstocks on the tree and crop characteristics (e.g. TCSA, number of rootsuckers, yield (kg/tree)) of 'Honeycrisp' trees grown under a high-density planting system (907 tree/acre), and trained in a tall-spindle training system. The PI used the same block in 2019 and 2020 growing seasons to study the effect of rootstocks on fruit quality traits. The 2020 data indicated that rootstocks have no significant effects on fruit weight (gm), fruit diameter (mm), firmness (lb/inch2) or total solids. b)Examine the effects of 14 dwarfing and semi-dwarfing rootstocks on the nutrient content of 'Honeycrisp' apples as it relates to the occurrence of bitter pit disorder. To fulfill this goal, ten random fruits were collected one week before harvest from each tree. Fruits were triple-washed with distilled water to ensure all the Surround (kaolin clay) was removed from the fruit's surface. We measured the fresh weight of the ten apple fruit samples; then, we peeled each fruit's bottom half (the calyx end of the fruit) using a potato peeler. Peel samples from the ten fruits/tree were combined, and the fresh weight was measured. Peel samples were oven-dried at 60 oC for seven days. The samples were then stored in air-tight lunch bags and sent to Cornell University for nutrient analysis. No data has been received yet. The effect of rootstocks on bitter pit incidence was evaluated at harvest (for 40-45 fruit/tree/rootstock) and after three months of storage (for 25 fruit/tree/rootstock). Our 2020 data indicated that 'Honeycrisp' on B.10 rootstock had the least percentage of pitted fruits. No significant differences were observed among the other 13 rootstocks. Goal 4: To achieve this goal, the PI delivered a 30 min power-point presentation titled "Performance of apple and peach rootstocks in Virginia and other Mid-Atlantic states." to tree fruit growers and stakeholders in Virginia through five fruit schools in Southern, Central, and Northern Virginia during Feb 10-14, 2020.

Publications

• Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Marini, R.P., Baugher, T.A., Muehlbauer, M., Sherif, S., Crassweller, R. and Schupp, J.R., 2020. Verification and Modification of a Model to Predict Bitter Pit for HoneycrispApples. HortScience, 1(aop), pp.1-6.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: S. Sherif, K.S. Yoder, G.M. Peck '2020). Effects of dwarfing and semi-dwarfing apple rootstocks on the growth and yield of 'Gala', 'Fuji' and 'York' apples. Acta Horticulturae 1281. Doi:10.17660/ActaHortic.2020.1281.17
• Type: Other Status: Published Year Published: 2020 Citation: S. Sherif and K. Yoder. 2018. Support for 2019; New Rootstocks, Cultivars, and Training Systems for Virginia. Virginia Fruit. 4 pp. (May 2020).

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:fruit growers, nurseries, agricultural consultants, extension agents, industry representatives Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The PI has provided training to a field specialist and a wage employee working at the AHS Jr. Agricultural Research and Extension Center, Winchester, VA on collecting data for tree growth parameters (e.f. TCSA, tree height, and canopy spread) and fruit quality traits (e.g. fruit diameter, weight, firmness, color, ethylene content, TSS, and starch index)from different rootstock trials. How have the results been disseminated to communities of interest?The results obtained from various rootstock trials were disseminated to apple growers, extension agents, and extension specialists through a peer-reviewed research article, two trade journal articles, and an orchard meeting. In 2019, the PI conducted six fruit schools in Southern, Central and Northern Virginia; namely, Patrick-Carroll, Roanoke-Botetourt, Southside, Nelson-Albemarle, Madison-Rappahannock and Winchester fruit schools. The purpose of these schools was to educate fruit growers, nurseries and other stakeholders on the factors that affect the production, sustainability, and profitability of fruit crops in Virginia. More than 250 participants attended fruit schools; the majority of them were tree fruit growers, agricultural consultants, extension agents, and industry representatives. The PI also discussed with apple growers through an in-orchard meeting that was held in Central Virginia in May 2019, the data obtained from the 2018 investigations onto the NC-140 apple rootstock trial. What do you plan to do during the next reporting period to accomplish the goals?Plans for the 2020 growing seasons include: For goal 1, assess the effects of rootstocks and training systems on tree growth and survival, and crop yield and quality of 'Gala', 'Fuji' and 'Crimson Crisp' apples; Goal 2, collect data for the effect of tree spacing on tree growth and fruit quality of 'Fuji' apples; Goal 3, continue evaluating the effects of 14 dwarfing and semi-dwarfing rootstocks on fruit quality and bitter pit incidence in 'Honecycrip'; Goal 4, disseminate research findings to apple growers and stakeholders in Virginia through winter fruit schools, in-orchard meetings, and professional meetings.

Impacts
What was accomplished under these goals? Goal 1. Examine the effect of rootstocks and training systems on reducing the costs associated with establishing higher density apple orchards in Virginia. The three specific objectives related to this objective are: a) Evaluate the production efficiency of four dwarfing apple rootstocks (G.11, G.16, G.935, and G.890) in supported (i.e., tall spindle) versus non-supported (i.e., central leader) training systems. To achieve this goal, three scion varieties ('Aztec Fuji', 'Buckeye Gala' and 'Crimson Crisp') on five dwarfing and semi-dwarfing rootstocks (B.9, G.11, G.935, G.890 and/or G.16) were planted in the AHS Jr. AREC's research farm on April 20, 2018. For each scion-rootstock combination, two tree support systems (trellis & free-standing) were compared. Trees under each system were arranged in three blocks (five trees/rootstock-scion combination/block) and distributed in the orchard according to the randomized complete block design (RCBD). The rootstocks were planted at a spacing of 7.5 x 12 ft (484 tree/acre) for the free-standing system, and 4 X 12 ft (906 tree/acre) for the trellis system. For the free-standing, the trees were trained to a central leader system. For the trellis systems, trees were supported by conduit posts and four wires spaced at 2, 5, 8 and 11 ft from the ground, and were trained to a tall spindle system. Evaluation of tree growth (e.g. trunk cross-sectional area, TCSA, (cm2), tree survival) were conducted for all rootstock-scion combinations and training systems at planting, and in falls of 2018 and 2019. The analysis of all TCSA data in the 2018 and 2019 fall seasons indicated that among all the rootstocks, G.890 was the most vigorous rootstock, followed by G.935, G.11, and B.9. G.16 was used only for 'Crimson Crisp', so it was not included in the statistical analysis. Also, due to the difference in tree spacing between the free-standing and trellis systems, the comparison of TCSA means between the two systems was not included. However, the data generally show higher tree vigor in trees supported by trellis compared to those unsupported. Also, it was noted that 'Crimson Crisp' was generally less vigorous than 'Gala' and 'Fuji' in all the rootstocks and training systems examined. As for tree survival, most of the tree losses were associated with G.11 rootstock, irrespective of the scion variety or the tree support system. b) Examine the effect of different rootstocks on the yield and quality of three fresh market apple cultivars ('Fuji', 'Gala' and 'CrimsonCrisp'). There were no fruits to harvest this year. Indeed, the trees in this trial were chemically defruited this spring to allow tree architecture to develop properly and trees to fill their allotted space. Trees will be allowed to bear their first crop in the coming year, 2020. c) Estimate the economic costs and benefits of the examined rootstocks under different training systems and for the three apple cultivars. This goal is expected to be completed by the final year of this field trial (2023) Goal 2: Examine planting densities that would achieve the highest yield efficiency and fruit quality under Virginia's soil condition. This research objective would specifically aim to: a) Determine planting spacing that would achieve the highest and most-consistent annual yield of 'Fuji' apples. To achieve this goal, trees of 'Fuji' on M.9 rootstock were planted in 2012 in the AHS Jr. AREC, at Winchester, to evaluate the effect of different planting densities on tree and crop characteristics under Virginia's soil conditions. Trees were planted at 2, 3, 4, 5 and 6 feet between trees and 12 feet between rows to provide densities ranging between 605 to 1815 trees/acre. Trees were supported by a trellis system composed of five wires and conduit posts and were trained and pruned according to the tall spindle training system. This research trial was active for three years after planting but subsequently discontinued due to the moving of the former PI (Dr. Gregory Peck) to a different institution in 2015. Trees of this field trial have been well maintained during the last three years, but data collected from this experiment up to now is not sufficient to address the objectives of the current proposal, especially in regards to the effect of tree spacing on fruit quality, cumulative yield and yield efficiency. No data were collected from this block in the 2019 season due to labor shortage. b) Investigate the effect of different planting densities on fruit quality traits. No data were collected from this block in the 2019 season due to labor shortage. Goal 3: Examine the effect of apple dwarfing rootstocks on the quality attributes of fresh market apples. The three specific aims to be investigated are: a) Evaluate 14 dwarfing and semi-dwarfing rootstocks for their effects on the quality traits of 'Honeycrisp' apples grown in a high-density production system. To achieve this goal, 'Honeycrisp' scions grafted on 14 dwarfing and semi-dwarfing rootstocks (B.10, G.11, G.202, G.214, G.30, G.41, G.935, G.969, M.26 EMLA, M.9 T337, V.1, V.5, V.6, V.7) were planted in a commercial orchard (Saunders Brothers Orchard, Piney River) in Central Virginia in 2014 as a part of an NC-140 project that encompasses nine states. The purpose of this multi-state project was to evaluate the effect of different rootstocks on the tree and crop characteristics (e.g. TCSA, number of root suckers, yield (kg/tree)) of 'Honeycrisp' trees grown under a high-density planting system (907 tree/acre), and trained in a tall-spindle training system. The PI used the same block in 2019 to study the effect of rootstocks on fruit quality traits (e.g. fruit weight, diameter, firmness, crispness, color, starch pattern index, soluble solids, titratable acidity, pH). The 2019 data indicated that fruits on G.935 were significantly firmer than were fruits of other rootstocks. Significant differences among rootstocks were also observed in fruit size, diameter, starch index, and pH; with G.935 significantly segregating from other rootstocks in these traits. b) Examine the effect of 14 dwarfing and semi-dwarfing rootstocks on the nutrient content of 'Honeycrisp' apples as it relates to the occurrence of bitter pits. Unfortunately, the crop was too light in the 'Honeycrisp' block assigned for this research and therefore we could not collect enough fruits to assess the incidence of bitter pit in all rootstocks. Goal 4: Provide educational materials and decision-making tools to apple growers and stakeholders in Virginia for adoption of high-density production systems. To achieve this goal, the PI prepared along with other colleagues a research article on the effects of dwarfing and semi-dwarfing apple rootstocks on the growth and yield of Gala, Fuji and York apples. This article was accepted for publication in a peer-reviewed journal, Acta Horticulturae and is expected to be published in 2020.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2019 Citation: S. Sherif, K.S. Yoder and G.M. Peck. Effects of dwarfing and semi-dwarfing apple rootstocks on the growth and yield of Gala, Fuji and York apples. Acta Horticulturae
• Type: Other Status: Published Year Published: 2019 Citation: Trade Journal Articles S. Sherif and K. Yoder. 2018. Evaluation of growth and productivity characteristics of free-standing apple rootstocks. Project Support for 2018. Virginia Fruit. 4 pp. (May 2019).
• Type: Other Status: Published Year Published: 2019 Citation: Outreach Oral Presentations: S. Sherif. 2019. NC-140 Honeycrisp rootstock trial-2018 updates. Saunders Brothers Orchard, Piney River, VA. Attendance: 15
• Type: Other Status: Published Year Published: 2019 Citation: K. Yoder and S. Sherif 2018. Apple rootstock susceptibility to Tomato Ring Spot Virus (TmRSV) and latent viruses. Project Support for 2018. Virginia Fruit. 3 pp. (May 2019).