NC-140 ROOTSTOCK TRIALS AT THE UKREC (1998-present)

University of Kentucky Horticulture has participated in the NC-140 Regional Rootstock Research Project since nearly its inception. The NC-140 project seeks to enhance economically and environmentally sustainable practices in temperate fruit production by focusing on rootstocks. NC-140 is partially supported through the USDA’s National Institute of Food and Agriculture (NIFA) by the Multistate Research Fund established in 1998 by the Agricultural Research, Extension, and Education Reform Act (an amendment to the Hatch Act of 1888) to encourage and enhance multistate, multidisciplinary research on critical issues that have a national or regional priority. Participating universities and state agricultural experiment stations provide additional support and technical expertise by research and extension personnel to ensure the accomplishment of mission objectives and provide integral outreach, including electronic information transfer through web sites, written material for growers and others stakeholder groups, and numerous educational programs. As of 2025, with 27 years of operation, NC-140 is the longest continuously supported project of this type.

The first cooperative rootstock planting at the UKREC began in 1990 with Gerald R. Brown as project leader and Dwight Wolfe (hired: 1984, retired: 2024) as research specialist. Further plantings followed in 1993, 1994, 1997, 1999, 2002, 2003, 2009, 2010, and 2019. Joseph G. Masabni took over as project leader in 2002 followed by Douglas D. Archbold in 2009. Joe Masabni was stationed at the UKREC during his six-year lead while Doug Archibold was located on campus in Lexington. Doug Archibold retired in 2020. Brent Arnoldussen took over as project leader in 2024 and is stationed in Lexington. Each planting was evaluated for five to ten years depending on their success in adapting to Kentucky growing conditions and viability in accomplishing trial objectives. Over the years there has been a dramatic shift to trees on more dwarfing rootstocks and closer in-row and between-row spacings. Improved production efficiency, yield, fruit quality, and labor savings have become a priority.

Plantings

1990 apple cultivar/rootstock planting consisting of 5 cultivars on 6 different rootstocks and replicated 6 times per rootstock. Trees were spaced 8 ft apart with rows 16 ft apart.

1990 plum rootstock planting consisting of ‘Stanley’ plum on 10 different rootstocks and 7 replications per rootstock. Trees were spaced 16 ft apart within rows 20 ft apart.

1993 apple rootstock planting consisting of ‘Liberty’ on 6 rootstocks and 8 replications per rootstock. Trees were spaced 16 ft apart within rows 23 ft apart.

1994 apple semi-dwarf rootstock planting consisting of ‘Red Gala’ on six rootstocks and 10 replications per rootstock. Trees were spaced 13 ft apart within rows 18 ft apart.

1994 peach rootstock planting consisting of ‘Redhaven’ peach on 12 different rootstocks and eight replications/rootstock. Trees were spaced 16 ft apart within rows 20 ft apart.

1997 apple training system planting consisting of ‘Golden Delicious’ on M.9 rootstock with eight treatment combinations of French axe and slender spindle training systems with light, moderate, and heavy pruning regimens. Trees spacing was 8 ft apart within rose 16 ft 5 in. apart.

1999 dwarf and semi-dwarf apple rootstock planting consisting of two groups of apple rootstocks: i) dwarfing group with 11 rootstocks and planted on a 10 x 16 ft spacing; ii) a semi-dwarfing group with six rootstocks and planted on a 13 x 20 ft spacing.

2002 apple rootstock trial consisting of ‘Buckeye Gala’ on nine rootstocks with seven replications per rootstock. Trees were spaced 8 ft apart within rows 15 ft apart.

2003 apple rootstock and 2003 apple physiology trials consisting of two groups (both had ‘Golden Delicious’ as the scion cultivar): i) 11 rootstocks with four replications with two of each rootstock per replication, trees were planted on an 8 by 15 ft spacing; ii) five rootstocks with six replications per rootstock, trees were planted on an 8 by 15 ft spacing.

2009 peach rootstock trial comparing 14 rootstocks with ‘Redhaven’ as the scion cultivar. Eight trees of each rootstock were planted with eight replications per rootstock. Trees were planted on a 16 ft by 20 ft spacing.

2010 apple rootstock trial comparing 31 different rootstocks with four replications per rootstock and up to 3 of each rootstock per replication. ‘Aztec Fuji’ was the scion cultivar. Trees were planted on a 6 ft by 15 ft spacing.

2019 apple rootstock trial comparing 7 rootstocks with 3 trees of each rootstock in five replications. ‘Buckeye Gala’ is the scion cultivar. Trees were planted on a 3 ft by 13.5 ft spacing.

Extension Publications

Brown, G.R., and D.E. Wolfe. 1998 – 2001. Optimal training of apple trees for high-density plantings. Fruit and Vegetable Crop Research Report. University of Kentucky publication PR-410:12-13, PR-423: 19-20, PR-436:15-16, PR-452:15-16.

Brown, G.R., and D.E. Wolfe. 1998 – 2001. Rootstock and interstem effects on pome and stone fruit trees. Fruit and Vegetable Crop Research Report. University of Kentucky publication PR-410:8-11, PR-423:14-18, PR-436:13-14, PR-452:13-15, PR-470:28-30.

Masabni, J.G, G.R. Brown, and D.E. Wolfe. 2002. Optimal training of apple trees for high-density plantings. Fruit and Vegetable Crop Research Report. University of Kentucky publication PR-470:30-31.

Masabni, J.G, G.R. Brown, and D.E. Wolfe. 2002 – 2004. Rootstock and interstem effects on pome fruit trees. Fruit and Vegetable Crops Research Report. University of Kentucky publication PR-470:28-30, PR-488:41-43, PR-504: 36-38.

Masabni, J.G, and D.E. Wolfe. 2005 – 2008. Rootstock and interstem effects on pome fruit trees. Fruit and Vegetable Crops Research Report. University of Kentucky College of Agriculture, Agriculture Experiment Station publication PR-521:42-44, PR-538:43-44, PR-555:50-52, PR-572:31-33.

Wolfe, D., D. Archbold, J. Johnston, and G. Travis. 2009 – 2017. Rootstock effects on apple and peach tree growth and yield. Fruit and Vegetable Crops Research Report. University of Kentucky College of Agriculture, Agriculture Experiment Station publication PR-603:13-15, PR-608:14-16, PR-626:11-14, PR-656:13-15, PR-673:9-11, PR-688:8-9, PR-706:9-11, PR-721:14-17, PR-739:16-19.

Wolfe D, Archbold D, Becker D, Johnston J, Travis V. 2018. Rootstock effects on apple tree growth and yield. 14–16. In: Snyder J, Rudolph R, Smigell C, Strang J (eds). Fruit and vegetable 2018 annual research report. Univ Kent Agr Exp Stn Bull. PR-757. https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/PR757.pdf.

Wolfe D, Archbold D, Becker D, Johnston J, Travis V. 2019. Rootstock effects on apple tree growth and yield. 14–16. In: Snyder J, Smigell C, Strang J (eds). Fruit and vegetable 2019 annual research report. Univ Kent Agr Exp Stn Bull. PR-762. https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/PR762.pdf.

Wolfe D, Archbold D, Becker D, Travis V. 2020. Rootstock effects on apple tree growth and yield. 4–6. In: Rudolph R (ed). Fruit and vegetable 2020 annual research report. Univ Kent Agr Exp Stn Bull. PR-779. https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/PR779.pdf.

Wolfe D, Becker D, Travis V. 2021. Rootstock effects on apple tree growth and yield. 6–10. In: Rudolph R (ed). Fruit and vegetable 2021 annual research report. Univ Kent Agr Exp Stn Bull. PR-798. https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/PR798.pdf.

Wolfe D, Becker D, Travis G, Arnoldussen B. 2023. Rootstock effects on apple tree growth and yield. 4–5. In: Rudolph R (ed). Fruit and vegetable 2023 annual research report. Univ Kent Agr Exp Stn Bull. PR-832. https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/PR832.pdf.