selling or planting of certain Ribes species or cultivars, particularly the nonnative European black currant, R . nigrum , that has been found to be extremely susceptible to WPBR ( Barney and Hummer, 2005 ; McKay, 2000 ). One source of immunity to C
Todd A. Burnes, Robert A. Blanchette, Jason A. Smith, and James J. Luby
Eric T. Wolske, Bruce E. Branham, and Kevin J. Wolz
leaf area and decreasing leaf thickness. As the level of shading increased, plant yield decreased, and the authors concluded that shade levels should be no more than 60% for blueberries to remain economically viable. Black currants ( Ribes nigrum ) have
Fumiomi Takeda, Rajeev Arora, Michael E. Wisniewski, Glen A. Davis, and Michele R. Warmund
A seasonal study was conducted to assess the freezing injury of `Boskoop Giant' black currant (Ribes nigrum L.) samples from Oct. 1991 through Mar. 1992. Buds were subjected to either differential thermal analysis (DTA) or one of a series of temperatures (0 to -36C). Freeze injury was then assessed either visually or with TTC. Results indicated that black currant floral buds have multiple low-temperature exotherms (LTE). Freeze injury in intact buds could not be visually quantified because of the lack of visible browning, nor assayed with TTC reduction. Excised floral primordia incubated in TTC, however, developed colored formazan following exposure to nonfreezing and sublethal freezing temperatures, but remained colorless when exposed to lethal temperatures. The percentage of floral primordia that were colored and colorless were tabulated and a modified Spearman-Karber equation was used to calculate the temperature at which 50% of floral primordia were killed (T50 The T50 temperature was correlated with the temperature at which the lowest LTE was detected (R2 = 0.62). TTC reduction assay using excised floral bud primordia was a good indicator of viability in frozen blackcurrant buds. Chemical name used: 2,3,5-triphenyltetrazolium chloride (TTC).
The search for appropriate white pine blister rust (WPBR) (Cronartium ribicola J.C. Fischer) resistant germplasm to use in black currant (Ribes nigrum L.) breeding programs began in 1935 in Ottawa. Crosses were made in 1938 and 1939 with three different Ribes L. species and two standard black currant cultivars. The resulting seedlings from these crosses were evaluated for rust resistance. Three promising selections resulted from this program and were named `Coronet', `Crusader' and `Consort'.
Black currant (Ribes nigrum L.) plants of eight varieties were grown either through black plastic mulch or in bare soil and with the area between the rows cultivated or sodded with red fescue (Festuca rubra L.). Over 6 years, black plastic mulch increased yields by 26% over no mulch and cultivation between the rows increased yield by 32% compared to sod. The effect of both treatments was additive, cultivation and black plastic increased yield by 68% over grass and no black plastic. Growers are recommended to plant black currants through black plastic and avoid using sod between the rows.
John Carter and Kim E. Hummer
Black currant (Ribes nigrum L.) cultivars with heavy, light, and no gooseberry mite (Cecidophyopsis grossulariae Collinge) infestation levels (MIL) were tested for cold hardiness by visually determining the bud injury rating (BIR) after laboratory freezing in Jan. 1998. Lightly mite-infested cvs. Blackdown and Risager, usually thought of as less cold hardy than Nordic cultivars, survived -35 °C, while mite-infested buds of the Finnish cv. Brödtorp were injured at -35 °C. Heavily mite-infested buds of the Swedish R. nigrum L. cv. StorKlas from Corvallis, Ore., were injured at -20 °C while lightly infested buds were injured to -25 °C. Noninfested `StorKlas' buds from Pennsylvania and British Columbia survived laboratory freezing to -35 °C. Heavy mite infestation lowered the bud cold hardiness of `Brödtorp' and `StorKlas' by 10 °C, as estimated by a modified Spearman-Karber T50, relative to the hardiness of lightly mite-infested buds of these cultivars. Heavily mite-infested buds contained unusual tissues forming what appeared to be spherical blisters or eruptions, ≈100 μ in diameter. Other tissues in the region of heavy mite infestation appeared to be more turgid than their noninfested counterparts. Abiotic and biotic stresses can have a combined impact on field-grown black currants.
Fumiomi Takeda, R. Arora, M. Wisniewski, and M. Warmund
`Danka' black currant floral buds produce multiple low temperature exotherms (LTEs). However, the absence of visual injury symbtoms in the buds after exposure to subfreezing temperatures make it difficult to assess injury in these buds. A 2,3,5-triphenyltetrazolium chloride (TTC) reduction assay was used to determine whether LTEs corresponded to freezing injury of individual floral primordia or to the entire floral axis. Intact buds were cooled at 3C/n, removed at 3C intervals from -12 to -33C, and thawed on ice for 24 h. Duplicate samples were subjected to differential thermal analysis. Freeze injury Could not be measured with TTC in thawed, intact buds. However, incubation of excised floral primordia in TTC resulted in an all or nothing response. The number of LTES did not correspond to the number of floral primordia killed within a floral bud, but the median LTE did correspond with the temperature at which lethal injury of the whole inflorescence occurred. Therefore, preliminary results indicate that TTC reduction assay of individual floral buds is a fast, reliable technique to assess bud injury.
Stanislaw Pluta and Agata Broniarek-Niemiec
Field resistance to white pine blister rust (WPBR) (Cronartium ribicola J. C. Fischer) was investigated on 53 black currant (Ribes nigrum L.) genotypes (cultivars and breeding selections) in 1998 and 1999. Uredia did not form on the black currant `Titania' and 17 advanced selections during field evaluations made at the Experimental Orchard at Dabrowice, near Skierniewice, Poland.
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'.
Attila Hegedűs, Emőke Balogh, Rita Engel, Béla Zoltan Sipos, János Papp, Anna Blázovics, and Éva Stefanovits-Bányai
several cultivars of important berry species (strawberry, raspberry, red and black currant) as compared with apple, a more intensively consumed fruit. This study revealed correlations between several redox parameters and provides information relative to