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Curt R. Rom, R. Andy Allen, and Bryan Blackburn

The Arkansas tree fruit research program has a history of involvement in rootstock development. The elements of rootstock development are rootstock cultivar testing and rootstock breeding and evaluation. Research is focused on apple and peach rootstocks. Rootstock testing is done in conjunction with the NC-140 cooperative uniform rootstock research project. Currently, there are 10 NC-140 trials in progress for apples, peaches, pears, and cherry rootstocks in Arkansas. The Arkansas rootstock breeding projects were established in the early 1970s as components of the fruit breeding program. The objectives are to develop apple and peach rootstocks which are adaptable to the Arkansas edaphic and adaphic conditions, have size control, have some degree of pest resistance, and are efficient in production. To date, 92 apple rootstock selections have been made and 41 are still in early evaluation for propagation and growth characteristics, while 56 peach rootstocks have been selected and are in early evaluation. Arkansas apple rootstocks selections are sequentially numbered with numbers preceded by AAR (ex: AAR-92). Peach rootstocks selections are numbered with numbers preceded by APR. Data from 2 NC-140 apple rootstock trials were presented and discussed.

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David H. Byrne

Despite the hundreds of existing stone fruit (Prunus spp.) cultivars used for fresh market, there is a continuing need to develop new stone fruit cultivars as the requirements of the industry change. Over the last 20 years there has been a shift toward private breeding as the public sector decreases its support of these long-range programs. As a result there are fewer public breeding programs and many of those still operating protect their releases and partially fund their programs with royalty payments. Other trends that are shaping the development of new stone fruit cultivars are a need for smaller or more easily managed tree architecture, a trend toward the use of fewer agricultural chemicals, the expansion of production zones into the milder winter zones to allow year-round availability of stone fruit, a general diversification of fruit types being marketed, the increased awareness of the health benefits of fruit consumption, the need for better and more consistent quality, and given the global marketing of these fruit the increased need for enhanced postharvest qualities. The breeding programs of the world are responding to these trends and working toward developing the cultivars for the world markets of the future.

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Michael W. Smith, William D. Goff, and M. Lenny Wells

-run seed of advanced breeding line selections and desirable cultivars were planted during the same winter-established trees were removed. ‘Creek’ trees were 1.2 m to 1.5 m tall when transplanted, and seedlings were 0.5 m to 0.6 m tall. Seedling trees were

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H.S. Aldwinckle, P.L. Forsline, H.L. Gustafson, and S.C. Hokanson

51 POSTER SESSION 2A (Abstr. 068–084) Breeding & Genetics—Fruits/Nuts, Small Fruit/Viticulture

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Yuee Tian, Zhiping Che, Di Sun, Yuanyuan Yang, Xiaomin Lin, Shengming Liu, Xiaoyu Liu, and Jie Gao

breeding. Materials and Methods Plant materials. Fifteen tree peony cultivars of different flowering time were tested for resistance to B. cinerea . According to the time of initial flowering, the 15 cultivars belong to three types: early flowering, middle

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Thomas G. Beckman, Jose X. Chaparro, and Wayne B. Sherman

-indexed budwood is available from National Virus-Tested Fruit Tree Program, WSU-IAREC, 24106 N. Bunn Road, Prosser, WA 99350-9687. Literature Cited Beckman, T.G. Lang, G.A. 2003 Rootstock breeding for stone fruits Acta Hort

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Tom DeGomez and Michael R. Wagner

Robinia L. (locust) species are among the most widely planted tree species in the world because they are ornamentally attractive, drought tolerant, fast growing, fix nitrogen, have very hard durable wood, and are adaptable to many sites and climates. Recent taxonomic analysis indicates there are four species, black locust (R. pseudoacacia L.); bristly locust (R. hispida L.); clammy locust (R. viscosa Vent.); and new mexican locust (R. neomexicana A. Gray). All four species originate in the southern United States and northern Mexico. Many horticultural cultivars are available. Locusts are tolerant of a wide range of soil types so long as there is good drainage, adequate moisture, and it is not very clayey. The environmental tolerance of locust makes it an excellent candidate for horticultural uses and for future breeding and selection to enhance its many desirable traits. It is easy to propagate via seed, root cuttings, soft- or hardwood cuttings, budding/grafting, or tissue culture. Locust has indeterminate growth. Spacing of plants in plantations is critical for the production of multiple products including high value timber. Locust is known for its ability to withstand drought conditions however at the cost of leaf shedding. Black locust contributes high levels of nitrogen to the soil from nitrogen fixing bacterial symbiosis. The major drawback to large-scale production of black locust in its native range is the damage that occurs from the locust borer (Megacyllene robiniae Forster). When planted outside the range of the locust borer it can be grown successfully as landscape specimen trees and as trees large enough for lumber production when varieties with straight trunks are grown. Damage from locust leaf miner (Odontata dorsalis Thunberg) can greatly detract from the trees ornamental qualities. Its most common use is as a site reclamation species. The tree is also used in honey production. The wood is highly decay resistant and is greatly valued for poles and posts. The wood is extremely hard and easy to work making it highly desirable for many construction uses.

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I.A. Merwin, D.A. Rosenberger, C.A. Engle, D.L. Rist, and M. Fargione

Natural (hay, wood chips, recycled paper pulp) and synthetic (polypropylene film and polyester fabric) mulches were compared with mechanical tillage and residual herbicides as orchard groundcover management systems (GMSS). In two New York orchards-the Clarke farm and Hudson Valley Lab (HVL—GMSS were applied from 1990 to 1993 in 1.8-m-wide strips under newly planted apple (Malus domestica; `Liberty', `Empire', `Freedom', and advanced numbered selections from the disease-resistant apple breeding program at Geneva, N.Y.) trees. GMS impacts on soil fertility, tree nutrition and growth, yields, crop value, and vole (Microtus spp.) populations were evaluated. After 3 years at the Clarke orchard, extractable NO3, Mn, Fe, B, and Zn concentrations were greater in soil with herbicides than synthetic mulches; soil K and P concentrations were greater with herbicides and wood chips than synthetic mulches. At the HVL orchard, topsoil NO3, K, and Mg concentrations were greater with hay mulch than herbicides or other mulches; Mg, Fe, and B concentrations were lower in soil with wood chips than other GMSs. Soil organic matter content was not affected by GMS. Apple leaf N, K, Cu, and Zn concentrations were greater with herbicides, hay mulch, and polypropylene mulch than cultivation or recycled paper mulch at the HVL orchard during hot, dry Summer 1991. Despite transient differences among GMSS during the initial years, after 4 years of treatments there were no consistent GMS trends in cumulative tree growth or gross yields. The higher establishment and maintenance costs of several mulches were offset by their prolonged efficacy over successive years; crop market values from 1992 to 1994 were considerably greater for trees with polypropylene film, polyester fabric, and hay mulches than herbicides, cultivation, or other mulches. Voles caused more serious damage to trees in synthetic and hay mulches, despite the use of mesh trunk guards and rodenticide bait.

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Jeff Olsen

Hazelnuts in Oregon are grown on 30,000 acres by ≈1000 orchardists in the Willamette Valley. Their annual production accounts for 3% to 5% of the world's hazelnut tonnage. The trees are grown in a single trunk system wrtb an average spacing of 20 feet between trees. Mechanical harvestihg is done in October. The industry employs an Integrated Pest Management approach, utilizing combinations of scouting, trapping, and biological control. The main insect pests are filbertworm, filbert leafroller, obliquebanded leafroller, and filbert aphids. The aphid parasite Trioxys pallidus was imported from Europe and successfully established in Oregon. Eastern Filbert Blight, Anisogramma anomala, a fungus disease, is the most serious disease problem in the industry. Annual applications of nitrogen to the soil and boron applied to the foliage are routine for Oregon's hazelnut growers. OSU research has quantified the importance of good light distribution in the tree canopy for increased nut production. OSU recommends a 5-year rotational pruning program. Some growers use mechanical hedging instead of hand pruning. OSU is home to the world's largest hazelnut breeding program. `Barcelona' is still the main, cultivar grown, while `Ennis' is the main in-shell variety. There is growing interest in planting varieties with a high percent kernel, such as `Casina', `Willamette', and `Lewis'.

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T.E. Thompson and L.J. Grauke

Precocity of pecan [Carya illinoinensis (Wangenh.) C. Koch] seedlings (year of first fruit production) was studied in relation to original seed measurements (nut weight, buoyancy, volume, and density) and in relation to growth index (GI) measurements of seedling trees for 4 years. A total of 2,071 pecan seedlings, representing nine controlled-cross families, were studied. Original seed measurements were not related to precocity of resultant seedling trees; but seed weight, buoyancy, and volume were significantly correlated with seedling growth rates. Nut density was negatively related to growth of seedlings. These relationships show the importance of original seed measurements and seed parentage in determining seedling growth, and have direct relevance in pecan nursery operations to increase general rootstock seedling vigor. Seedling growth rate was significantly correlated to precocity levels, with measurements taken in the later years of the study showing the highest correlations with precocity. This strong growth-precocity relationship may have negative genetic implications since a common breeding objective is to produce more precocious cultivars that maintain smaller tree size in mature orchards.