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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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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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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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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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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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C.M. Ronning, D.M. Harkins, R.J. Schnell, and L.H. Purdy

Cacao is an important crop in the tropics, but its breeding has been hampered by a lack of understanding of its genetics. One result of this has been the introduction of “hybrid” trees which did not perform predictably under various environmental conditions. We are studying the inheritance of isoenzyme, RFLP, and Random Amplified Polymorphic DNA (RAPD™) markers in order to estimate the genetic relationships among and between populations. Our objectives include determining if any linkage exists between these molecular markers and witches' broom (Crinipellis perniciosa) resistance, a major disease of cacao.

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T. van der Zwet and R.L. Bell

During 1976-1980, three plant exploration trips were made throughout eastern Europe in search of native Pyrus germplasm. A total of 384 accessions (231 from Yugoslavia, 86 from Romania, 43 from Poland, and 12 each from Hungary and Czechoslovakia) were collected as budwood and propagated at the National Plant Germplasm Quarantine Center in Glenn Dale, Md. Following 8 years of exposure to the fire blight bacterium [Erwinia amylovora (Burr.) Winsl. et al.], 17.49” of the accessions remained uninfected, 11.2% rated resistant, 6.8% moderately resistant, and 64.6% blighted severely (26% to 100% of tree blighted). Some of the superior accessions have been released for use in the pear breeding program.

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James N. Moore, Roy C. Rom, Stanley A. Brown, and Gerald L. Klingaman

Three ornamental peaches and one ornamental nectarine were released in 1992 from the Arkansas peach breeding program. `Tom Thumb' is a red-leaf dwarf peach with attractive foliage that is retained throughout summer. `Leprechaun' is a green-leaf dwarf nectarine with small but attractive, freestone fruits. `Crimson Cascade' and `Pink Cascade' are red-leaf peaches with trees of standard size that exhibit a weeping growth habit. `Crimson Cascade' produces double flowers that are dark red while `Pink Cascade' double flowers are pink. The attractive plants of these cultivars should be of value in home landscapes.