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Kim E. Hummer and Deric D. Picton

Powdery mildew (Sphaerotheca mors-uvae) severely infects young shoots and leaves of black currants (Ribes nigrum) and red currants (R. rubrum) in the Pacific northwestern U.S. Environmentally sound control measures are being sought as alternatives to sulfur or demethylation-inhibiting fungicides. This study examined the effect of mineral oil spray on powdery mildew infection in susceptible black and red currants. Mineral oil at 8 mL·L-1(8000 ppm) was applied to plants until runoff at 0-, 2-, and 4-week intervals from April through June in 1999 and 2000 on eight currant cultivars growing in Corvallis, Ore. Shoot and leaf surfaces were rated for powdery mildew incidence in early July both years. Oil applications significantly reduced mildew severity in vegetative growth as compared with that of the unsprayed control. The disease control from 2-week interval and 4-week interval oil applications was not significantly different.

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Michele Warmund, Milon George, and Fumiomi Takeda

Differential thermal analyses (DTA) and freeze viability tests were conducted to investigate the biophysics of freezing in floral buds of `Danka' black (Ribes nigrutn L.) and `Red Lake' red currants [Ribe.s sativum (Rchb.) Syrne] sampled from Nov. 1989 through Mar. 1990. Scanning electron microscopy was also used to determine the relationship between floral morphology and the freezing characteristics of the buds. Floral buds had multiple abrupt low-temperature exotherms (LTEs) and one or two broad LTEs in DTA tests. Abrupt LTEs from DTA were associated with apparent injury to the inflorescence in viability tests. The number of LTEs did not correspond to the number of racemes or flowers per bud, indicating that several flowers froze simultaneously. DTA experiments conducted in Dec. 1990 revealed that the broad exotherm detected between - 14 and - 20C in `Danka' samples resulted from freezing of supercooled water in the outer nonliving region of the periderm of cane tissue attached to the bud.

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Adam Dale

Fruit from black, red and white currants, and gooseberries (Ribes L.) were grown commercially in North America at the beginning of the 20th Century. However, when white pine blister rust (WPBR) (Cronartium ribicola J. C. Fisch.) was introduced into the new world, their cultivation was discontinued. About 825,000 t (908,000 tons) of Ribes fruit are produced worldwide, almost entirely in Europe. The fruit is high in vitamin C, and is used to produce juice, and many other products. Now a wide range of imported Ribes products is available particularly in Canada, and the pick-your-own (PYO) market is increasing. Two diseases, powdery mildew [Spaerotheca mors-uvae (Schwein.) Berk. & Curt.] and WPBR, are the major problems encountered by growers. Fortunately, many new cultivars are resistant to these two diseases. Commercial acreage of Ribes in North America is located where the growing day degrees above 5 °C (41 °F), and the annual chilling hours are at least 1200. Initially, the Ribes industry will develop as PYO and for farm markets. But for a large industry to develop, juice products will needed. Our costs of production figures indicate that about 850 Canadian dollars ($CDN) per 1.0 t (1.1 tons) of fruit will be required to break even.

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Moritz Knoche, Eckhard Grimm, and Henrik Jürgen Schlegel

canescens Bois) or from field-grown european plum (‘Doppelte Hauspflaume’ grafted on Prunus insitia L. ‘St. Julien A’), gooseberry (‘Invicta’), red currant (‘Rovada’), black currant (‘Titania’), and blueberry (‘Elliott’) at the Horticultural Research

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Wes Messinger, Aaron Liston, and Kim Hummer

The Pacific Northwest boasts a remarkable diversity of wild currants and gooseberries (Ribes). Of nearly 150 species worldwide, 34 occur in the region. All but two infrageneric taxa are represented, including close relatives of the black currants, red currants, and cultivated gooseberries. High ecological diversity parallels this taxonomic diversity: a Ribes species occurs in nearly every terrestrial habitat, from sea level to above treeline, and from swamp to desert. This diversity is a valuable source of agronomically important genes for the plant breeder. In addition, wild Ribes represent a relatively unexplored source of ornamental shrubs. Habit and habitat of a number of species of interest are described and illustrated. An annotated list of species, subspecies, and varieties native to the Pacific Northwest is presented with discussion of taxonomic proximity to Cultivated varieties, range, natural habitat, and ornamental potential.

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Paul J. Zambino

Artificially inoculated single-leaf cuttings and small plants consistently differentiated european black currant (Ribes nigrum L.) cultivars susceptible to white pine blister rust (WPBR; Cronartium ribicola J.C. Fisch.) from immune cultivars carrying the Cr resistance gene. Black currant cultivars Consort, Crusader, and Titania showed no signs of infection with any of 21 strains of WPBR, suggesting that strains able to overcome immunity conferred by the Cr resistance gene, if they exist, are uncommon in North America. However, in red currant (Ribes rubrum L.), two sources of material presumed to represent the immune cultivar Viking showed no resistance to infection. All rust strains infected and sporulated as if the cultivar were fully susceptible, casting doubt on the true identity of available sources of `Viking'.

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Kim E. Hummer, Joseph D. Postman, John Carter, and Stuart C. Gordon

During Dec. 1997 and Jan. 1998, the gooseberry mite, Cecidophyopsis grossulariae Collinge, was observed to infest 48 currant and gooseberry (Ribes L.) cultivars in a field plantation in Corvallis, Ore. The mite was observed on 29 black currant, (Ribes nigrum L.), two red currant [Ribes rubrum L. and R. sativum (Rchbch.) Syme], 12 gooseberry [R. uvacrispa L., R. oxyacanthoides var. setosum (Lindley) Sinnot], and three R. ×nidigrolaria Bauer cultivars and the hybrid R. nigrum × R. pauciflorum Turcz. ex Pojark. A range of mite infestation levels was observed, with some cultivars not being infested, some with light infestation, having 1 to 100 adult mites per bud, and some heavily infested, with more than 100 mites per bud. On lightly infested buds, the mites were inside bud and leaf scales; in heavily infested buds, mites were also observed on floral primordia. Scales of infested buds were often loose and appeared more open than noninfested ones. Mite distribution varied by branch within a plant. Black currant cultivars with the heaviest infestation of C. grossulariae were of Scandinavian, Russian, Scottish, and Canadian origin. The Russian black currant cultivar Tunnaja was the most heavily infested with more than 1000 mites per bud. Floral primordia were damaged in heavily infested buds.

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Attila Hegedűs, Emőke Balogh, Rita Engel, Béla Zoltan Sipos, János Papp, Anna Blázovics, and Éva Stefanovits-Bányai

’), raspberry (‘Glen Ample’, ‘Malling Exploit’, and ‘Fertődi zamatos’), red currant (‘Detvan’, ‘Jonkheer van Tets’, and ‘Rondom’), and black currant (‘Fertődi 1’, ‘Otelo’, and ‘Titania’) as well as apple cultivars (Jonathan, Golden Delicious, and Granny Smith

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Franco Famiani and Robert P. Walker

other soft fruit, such as ripe blueberries ( Vaccinium corymbosum L.) and red currants ( Ribes rubrum L.), in which the abundance of these enzymes was established in a previous study ( Famiani et al., 2005 ). Materials and Methods Plant

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Todd A. Burnes, Robert A. Blanchette, Jason A. Smith, and James J. Luby

; Zambino, 2000 ). After field evaluations, a red currant ( Ribes rubrum L.) cultivar, ‘Viking’ was thought to have immunity to C. ribicola ; however, uredinial sori developed after artificial inoculations ( Zambino, 2000 ). It was suggested that an error