Gooseberries and currants belong to the genus Ribes and include many native species and cultivars used for ornamental plantings and fruit production in North America. Breeding programs in North America and Europe have focused on producing Ribes with desired juice quality, winter hardiness, cultural characteristics, and pest resistance, including tolerance to insects, viruses, and fungi (Brennan, 1995; Dale, 2000; Hummer and Barney, 2002).
Several native and nonnative species of Ribes can serve as alternate hosts for Cronartium ribicola, the causal agent of white pine blister rust (WPBR). This disease was introduced into North America over 100 years ago and has caused major mortality to native five-needle pines. Once the Ribes leaves are infected with aeciospores from the pine, they develop uredinia that produce urediniospores that reinfect Ribes leaves during the summer months (Sinclair et al., 1987). This is followed by the production of telia and basidia in late summer and fall. Basidiospores from basidia do not travel long distances and infect pines through needle stomata (Sinclair et al., 1987). One method of control of this disease in the United States and Canada has been to eradicate native and cultivated susceptible Ribes in areas where five-needle pines grow. This has been discontinued because of its cost and lack of evidence that eradication was successful to reduce the incidence of WPBR (Maloy, 1997). Fifteen states have regulations that prohibit 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. ribicola in Ribes originates from the dominant Cr gene derived from R. ussuriense (Knight et al., 1972). Ribes ussuriense is very closely related to R. nigrum (considered by some to be a variety) and has been used in breeding programs to develop immune cultivars with characteristics similar to R. nigrum. There are several named cultivars that originated this way, including ‘Consort’, ‘Coronet’, and ‘Crusader’ (Hunter, 1955). Many Ribes cultivars are sold in nursery centers and promoted for their cultural characteristics and WPBR resistance. Several field and artificial inoculation studies have been completed to determine the relative susceptibility of Ribes cultivars to WPBR (Hummer, 1997, Pluta and Broniarek-Niemiec, 2000; 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 in labeling or propagation may have occurred and it was wrongly designated as immune. Recently, fingerprinting techniques using random amplified polymorphic DNA and intersimple sequence repeat markers have become available to determine relatedness of Ribes genotypes (Lanham et al., 2000). This technology is useful for verifying accuracy of clones and resistant genotypes.
During a previous study (Burnes et al., unpublished data), it was determined that plants being sold as R. nigrum ‘Consort’ by a wholesale nursery in the United States were very susceptible to WPBR after artificial inoculations. These plants, however, were being marketed as “immune.” The objectives of this study were to 1) determine the susceptibility and genetic relatedness of three ‘Consort’ accessions and 2) determine the WPBR susceptibility of 16 Ribes clones in the field and after artificial inoculations.
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