Black currant clonal identity and white pine blister rust resistance

Abstract

Gooseberries and currants (Ribes L.) are the alternate hosts for the fungus Cronartium ribicola J. C. Fischer, the causal agent of white pine blister rust. In this study, 16 black currant (R. nigrum L.) cultivars, including three accessions of the putatively immune cultivar 'Consort' and three cultivars developed at the University of Minnesota Horticultural Research Center, were screened for resistance to C. ribicola using artificial inoculation procedures. Twelve of these cultivars were grown in the field and observed for natural infection. Cultivars 'Ben Sarek', 'Ben Lomond', and 'C2-2-1' were infected naturally in the field at the University of Minnesota Horticultural Research Center in 2000, 2001, and 2004. Cultivars 'Ben Sarek', one mislabeled 'Consort' accession, R. nigrum 'WI-1', and 'Ben Lomond' had significantly more uredinial sori than other cultivars when inoculated artificially. To determine if the infected and noninfected 'Consort' clones were genetically related, DNA microsatellite genotyping was carried out to fingerprint these clones. One of the six microsatellite loci resulted in a polymorphism that indicated the infected clone was genetically different from the noninfected clones. In addition, the inoculation procedures used in these studies are generally efficacious for predicting resistance in the field because none of the field-infected cultivars were resistant in the greenhouse. This study confirms the Cr gene for resistance to C. ribicola in Ribes has remained effective for over 50 years.