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R.E. Worley

`Oconee' is a `Schley' × `Barton' cross from the USDA pecan breeding program and was tested as selection 56-7-72. It first bore in its 5th leaf and yields increased each succeeding year except year 11. Yields exceeded 23 kg/tree in year 10 and 12 and nut quality has been excellent each year. Percentage kernel averaged 56 with 26% (of inshell nut) grading fancy and 2% grading amber. `Oconee' is large with nuts averaging 9.7 g in wt. and 13 cc in volume with 71% 2.54 cm or larger in diameter. After mechanical cracking, nuts are easily shelled into large unbroken kernel halves. `Oconee' will pollinate `Cape Fear', `Stuart', `Desirable', `Kiowa' and `Sumner'. It is pollinated by `Sumner', `Stuart', `Maramek', `Kiowa', `Gloria Grande' and `Forkert'. `Oconee' should make an excellent temporary tree. More years data are needed to assess its merits as a permanent tree.

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L.A. Wasilwa, N. Ondabu, G.W. Watani, H. Mulli, S. Kiiru, A. Nyagah, and Kagiri

Several outstanding macadamia trees (Macadamia integrifolia Maiden and Betche, M. tetraphylla L. S. or hybrid of these two species) were selected from orchards established in the 1960s in the central and eastern highlands and evaluated over a period of 10 years. In the thrid year of these evaluations, clones from 30 high-yielding trees (40 to 90 kg) were propagated by grafting and trials were established in the central and eastern highlands. Three to five Hawaiian varieties were included as controls. Each trial consisted of five to 10 trees of each clone. Trees were evaluated for vigor, flowering, age of bearing, and yield. From these tests, a subset of 10 of the most outstanding clones were selected and evaluated in 25 field trials located in the Kenyan highlands. Most these clones started to bear 3 years after transplanting. Three distinct flowering patterns have been observed. Ten years after transplanting, yields ranged between 30 to 60 kg nuts/tree. The macadamia hybrids and M. tetraphylla performed best at the higher elevations (1700–1850 m), M. integrifolia clones performed best at elevations of 1500 to 1750 m. Only two Hawaiian varieties performed well and have been used in the breeding program. Most of the cultivated macadamia trees in Kenya are either M. integrifolia or hybrids. Cultivation of M. tetraphylla in Kenya is no longer recommended.

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J.D. Norton, Hongwen Huang, and Fenny Dane

The Chinese chestnut (Castanea mollissima Blume) is a valuable germplasm resource for horticultural traits such as resistance to chestnut blight (Cryphonectria parasitica), excellent quality, wide adaptation, and consistent high yield. The Chinese chestnut breeding program was established at Auburn Univ. in 1933 from nuts directly introduced from China by the USDA. A recurrent selection breeding program with progeny from the 1933, 1953, and 1991 plantings with selection for blight resistance, precocity, nut size, and storage quality, yield, and pest resistance. Cultivars released from the 1933 planting were `Alaling,' `Alamore', and `Black Beauty'. `AU-Cropper', `AU-Leader', and `AU-Homestead' were named from the 1953 planting. Two blight-resistant, precocious seedlings, AU-91-P1-26 and AU-P4-26, appear to be very promising selections for improvement of all Chinese chestnut cultivars for nut size and other selection traits. Since there is little information available regarding heritability of certain traits in perennial tree species, results of 65 years of breeding at Auburn Univ. should provide us with guidance for further improvement of selection traits in chestnut breeding.

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Gennaro Fazio, Herb S. Aldwinckle, Terence L. Robinson, and James Cummins

The Geneva® Apple Rootstock Breeding program, which was initiated in 1968 by Dr. James Cummins and Dr. Herb Aldwinckle of Cornell University and which has been continued as a joint breeding program with the U.S. Dept. of Agriculture Agricultural Research Service (USDA-ARS) since 1998, has released a new semi-dwarfing apple rootstock which is named Geneva® 935 or G.935. G.935 (a progeny from a 1976 cross of `Ottawa 3' × `Robusta 5') is a selection that has been widely tested at the New York State Agricultural Experiment Station in Geneva, N.Y., in commercial orchards in the United States and at research stations across the United States and Canada. G.935 is a semi-dwarfing rootstock that produces a tree slightly larger than M.26. G.935 is the most precocious and productive semi-dwarf rootstock we have released. It has had similar yield efficiency to M.9 along with excellent fruit size and wide crotch angles. It showed no symptoms of winter damage during the 1994 test winter in N.Y. G.935 is resistant to fire blight and Phytophthora; however. it is susceptible to infestations by woolly apple aphids. G.935 has shown tolerance to replant disease complex in several trials. It has good propagation characteristics in the stool bed and produces a large tree in the nursery. G.935 has better graft union strength than M.9, but will require a trellis or individual tree stake in the orchard to support the large crops when the tree is young. G.935 will be a possible replacement for M.26. Suggested orchards planting densities with this rootstock are 1,500-2,500 trees/ha. It has been released for propagation and sale by licensed nurseries. Liners will be available in the near future.

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R.N. Trigiano, M.T. Windham, and W.T. Witte

Powdery mildew (Microsphaera pulchra) of flowering dogwood (Cornus florida L.) has become a significant problem of trees in nursery production as well as in the landscapes and forests of the eastern United States. The disease significantly reduces growth and berry production by older established trees and may contribute to the inability of younger trees (liners) in production to survive winter dormancy. Disease resistance in named cultivars is limited to partial resistance found in `Cherokee Brave'—all other cultivars are extremely susceptible. Until now, the only disease control measure was to establish an expensive, labor-intensive, preventive fungicide program. We examined >22,000 seedlings and identified 20 that were extremely resistant to powdery mildew. Three trees with white bracts were selected from the 20 and released as patent-pending cultivars. `Karen's Appalachian Blush' has long, non-overlapping, pink fringed bracts with a delicate appearance. `Kay's Appalachian Mist' has creamy white, slightly overlapping bracts with deeply pigmented clefts. `Jean's Appalachian Snow' has large, strongly overlapping bracts with non-pigmented clefts. The three powdery mildew-resistant cultivars will be entered into an existing breeding program with `Appalachian Spring', a cultivar released by the Tennessee Agriculture Experiment Station and resistant to dogwood anthracnose, in an attempt to produce trees that are resistant to both diseases.

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Zhi-li Suo, Wen-ying Li, Juan Yao, Hui-jin Zhang, Zhi-ming Zhang, and Di-xuan Zhao

Tree peony cultivars are usually classified according to flower characteristics (flower form and flower color) which are commonly affected by environmental influences and developmental levels. Judgment of flower forms may also depend on the observer. Precise and rapid cultivar identification methods are also required to manage cultivar collections as well as tree peony breeding programs. The objective of this paper is to analyze the discriminatory ability of leaf morphology and Intersimple sequence repeat (ISSR) marker systems for tree peony cultivars. As a result, although there exist large variations of leaf morphology of tree peony cultivars, the morphological characteristics of biternately compound leaves 3, 4, and 5 from the base of a shoot at the middle part of a plant are relatively stable with smaller variations within cultivars (2.7% to 27.1%, 16.8% on average) and with larger differentiations among cultivars (72.9% to 97.3%, 83.2% on average). Statistical and principal components analyses indicate that 12 leaf morphological characteristics are valuable for cultivar classification. ISSR markers present a precisely discriminatory power in tree peony cultivar classification without environmental influences. The cultivars with multiple flower forms, which makes it difficult to make judgment by means of a flower-form-based classification system, have been significantly characterized using leaf morphology or ISSR markers.

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Nobuhiro Kotoda, Hiroshi Iwanami, Sae Takahashi, and Kazuyuki Abe

We thank Hiroaki Ichikawa, the National Institute of Agrobiological Sciences, for providing the binary vector pSMAK251, and Tomoko Sekita, the National Institute of Fruit Tree Science, for technical assistance. This work was supported by the

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J.D. Norton and Fenny Dane

The American or Allegeny chinquapin (Castanea pumila) is native to the same area of the United States as the American chestnut (C. dentata) from Florida to Canada and westward to Arkansas. The high-quality nuts are an excellent source of food for wildlife and humans. Resistance to chestnut blight (Cryphnuectria parasitica) was discovered in seedlings in virgin forest at Elgin Air Force Base, Fla., with observations of plants for 35 years. A recurrent selection breeding program was established at Auburn Univ. to improve the blight resistance, precocity, dwarfism, pest resistance, cold hardiness, yield, and quality. A number of seedlings appear to be very promising selections for improvement of the American chinquapin. Since there is little information available regarding hereditability of certain traits in perennial tree species, results of breeding at Auburn Univ. should provide us with guidance for further improvement of the American chinquapin.

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Uri Lavi, Emanuel Lahav, Chemda Degani, Shmuel Gazit, and Jossi Hillel

1 Dept. of Fruit Trees. 2 Dept. of Genetics. Contribution from the Agricultural Research Organization no. 3233-E 1991 series. The Israel Fruit Board provided financial support for this research. We thank the staff of the Akko and Bet Dagan

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Margaret R. Pooler

The U.S. National Arboretum has released over 650 new plant cultivars since it was established in 1927. A key to the success of the plant breeding program has been the voluntary participation of universities and private nurseries in evaluating and propagating new plant material. The cooperative evaluation and stock increase programs play a critical role in the successful testing, introduction, and distribution of new cultivars of landscape trees and shrubs. These integrated cooperative programs depend on the involvement of nurserymen, researchers, botanic gardens, or individuals to evaluate potential new cultivars under diverse climatic conditions and hardiness zones, and wholesale propagation nurseries to increase stock of those cultivars destined for release.