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Cecil Pounders, Tim Rinehart, and Hamidou Sakhanokho

interspecific hybrid cultivars ( Egolf, 1981a , 1981b , 1986a , 1986b , 1987 , 1990 ; Pooler, 2006a ; Pooler and Dix, 1999 ) that successfully combined the powdery mildew resistance of L. fauriei with other desirable horticultural traits from L. indica

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Chun-Yan Han, Gui-Fen Luo, Li Ji, Wei-Bang Sun, Xu-Yang Fu, and Cong-Ren Li

in Hunan ( Liao, 2007 ). Three cultivars, including M . ‘Yujin’, M . ‘Danxin’, and M . ‘Qinfang’, are interspecific hybrids between M. crassipes and M. yunnanensis . M. calcicola C. Y. Wu is an evergreen tree native to the subtropical

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

. ‘MP-29’ also provides a marked reduction in tree vigor compared with peach seedling type rootstocks and may prove useful as a semidwarf rootstock where a less vigorous tree is preferred. Origin ‘MP-29’ is an interspecific hybrid developed by the U

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Yuji Noguchi, Tatsuya Mochizuki, and Kazuyoshi Sone

The use of wild species as breeding materials was tried for expanding hereditary variation in strawberry. Some interspecific hybrids setting large fruits with peculiar aroma have been bred by pollination of F. vesca to F. xananassa. Although Asian wild diploid strawberries such as F. nilgerrensis or F. iinumae have not been exploited as a breeding material until the present, the crossing test between cultivated strawberries (8x) and the Asian wild strawberries (2x) were attempted. The interspecific hybrids originated from pollination of F. nilgerrensis or F. iinumae to F. xananassa cv. `Toyonoka' were all sterile pentaploids. By in vitro colchicine treatment of these sterile hybrids for chromosome doubling, many fruiting interspecific hybrids were produced. In particular, some superior hybrids were obtained from `Toyonoka' × F. nilgerrensis. From the results of RAPD analysis, the interspecific hybrids had the fragments specific for both parents. While their morphological characters were close to `Toyonoka', they had some characters from F. nilgerrensis, such as numerous hair on their petioles and peduncles. Their fruits have good characters that are same level of cultivated strawberry about size, Brix, acidity, and vitamin C content. The flesh is soft and skin color is pale pink. The aroma components are resemble F. nilgerrensis, and enrich ethyl acetate. The fragrance of interspecific hybrid like peach is characteristic.

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James K. Mitchell, W. Keith Patterson, and Robert H. Ford

European Vitis vinifera L. (four cultivars); interspecific hybrid (seven cultivars); and American V. aestivalis Michx. (one cultivar), V. labrusca L. (three cultivars), and V. rotundifolia Michx. (two cultivars) grapevines were tested for susceptibility to septoria leaf spot disease. V. rotundifolia cultivars Cowart and Fry exhibited hypersensitive-type resistance. All other American, European, and hybrid cultivars tested were susceptible with varying levels of disease severity. Cultivars with little (e.g., interspecific hybrid) or no (e.g., European) V. labrusca L. heritage were more susceptible to septoria leaf spot than American V. labrusca cultivars.

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M.M. Hossain, H. Inden, and T. Asahira

Pollen morphology was examined in amphidiploid and amphidaploid interspecific hybrids between Brassica oleracea L. and B. campestris L. Pollen of the amphidiploid interspecific hybrids between B. oleracea var. capitata and B. campestris var. pekinensis, and between B. campestris var. chinensis and B. oleracea var. capitata, were significantly longer and wider than those of their diploid parents, presumably due to the phenotypic expression of the hybrid genomes and ploidy effects. The exine ridges and pores of the amphidiploids were well-developed and significantly larger than those of their diploid parents, but they were poorly developed in the amphihaploids.

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Kelly M. Anon and Richard Craig

Interspecific hybrids of Exacum species (Gentianaceae) endemic to Sri Lanka possess excellent qualities for domestication as a new floriculture crop. The exact mode of floral induction and development responses are unknown, impeding the introduction of this potential crop. The interspecific hybrids evaluated are the result of controlled cross pollinations of E. macranthum. Arn. ex Griseb., E. trinervium (L.) Druce ssp. trinervium, and E. trinervium ssp. ritigalensis. (Willis) Cramer. The hybrids exhibit great genetic variability for horticultural traits. In addition, two growth and flowering patterns exist within the Penn State germplasm. Continuous-flowering genotypes flower throughout the year but more profusely and rapidly under late spring and summer conditions. In contrast, periodic-flowering genotypes exhibit two distinct seasonal habits. Under winter conditions, these accessions have a rosetted habit, much secondary branching, and few or no flowers. In summer conditions, they break their apical dominance, bolt, and produce flowers. As members of the Gentianaceae, Exacum hybrids produce an elegant blue flower with a striking yellow eye and bottle-shaped anthers. We evaluated the growth and flowering responses of Exacum interspecific hybrid accessions to photoperiod and irradiance. Accessions were evaluated under greenhouse conditions for floral production, rate of floral development, and growth characteristics. For the 20 accessions evaluated, supplemental irradiance under winter conditions resulted in greater floral production and much greater shoot and root mass accumulation. Little height and branching response occurred with supplemental irradiance. Of the 15 accessions evaluated under four photoperiod regimes, flowering and growth responses to photoperiod occurred under summer conditions but not in winter. An interaction among season, accession, and photoperiod revealed the complexity of Exacum germplasm and environmental responses.

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Glare J. Coyne and Shawn A. Mehlenbacher

Eastern filbert blight (EFB) (Anisogramma anomala) is a serious disease of the European hazelnut (Coryls avellana). A single dominant gene for immunity to EFB from C. avellana `Gasaway' is being combined with good nut and kernel traits using a modified backcross approach. Additional sources of resistance would be highly desirable. Clones and seedlings of six other species (C. columa, C. comuta, C. heterophylla, C. sieboldiana, C. amencana, and C. jaquemontii] and a few interspecific hybrid selections were screened in the greenhouse to identify new sources of resistance. C. jacquemontii seedlings and C. columa clones were highly susceptible. C. comuta, C. hetemphylla, and C. sieboldiana clones were resistant, as were 86% of the C. americana seedlings tested. Five C. americana × C. avellana hybrids from New York were resistant under field conditions. One of four C. comuta × C. avellana and two of three C. hetemphylla × C. avellana hybrids were resistant.

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L.J. Grauke and Richard D. O'Barr

`Oconee' pecan [Carya illinoinensis (Wangenh.) K. Koch] scions were grafted on seedling rootstock from nine open-pollinated seedstocks. Rootstock included three seedstocks each of pecan, water hickory [C. aquatica (F. Michx.) Nutt.], and their interspecific hybrid, Carya × lecontei (Little). Pecan seedlings had the largest basal diameters and water hickory seedlings the smallest. Seedlings of `Elliott' and `Curtis' seedstocks were larger than seedlings from `Moore' seedstock. Pecan and C. × lecontei seedlings were grafted more successfully than water hickory. Graft success varied among seedstocks of pecan and C. × lecontei Foliage color of seedlings, possibly indicative of iron nutritional status, was influenced by species; pecan seedling leaves were darker green than those of water hickory seedlings, but similar to C. × lecontei leaves. `Oconee' scion leaves were darker green on pecan rootstock than when grafted on C. × lecontei rootstock.

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James R. Ault

Shoot proliferation cultures were established in vitro using flower-stem explants from two different interspecific hybrid plants of Liatris. Explants taken on two dates from field-grown plants were successfully established and axillary shoot growth promoted on a medium consisting of Murashige and Skoog basal salts and vitamins with 30 g·L-1 sucrose, 1.0 μm BA, and 7.0 g·L-1 agar, with a medium pH = 5.7. Initial explant contamination rates were significantly higher among explants collected later in the growing season. Addition of BA (1.0, 2.0, 4.0, 8.0, or 16.0 μm) improved shoot formation compared to the control for both plants. Proliferation rates differed between the dates of establishment, the plants, and the BA treatments. Shoots rooted readily in medium without PGRs or with 1.0, 2.0, 4.0, or 8.0 μm K-IBA. Overall rooting was 88%. About 90% of the plants rooted in the presence of 1.0 μm K-IBA were successfully established in the greenhouse. Chemical names used: 6-benzyl adenine (BA); potassium salt of indole-3-butyric acid (K-IBA).