Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2002
Publication Date: 8/15/2002
Interpretive Summary: Some currants and gooseberries in the field collection of the U.S. Department of Agriculture, Agricultural Research Service in Corvallis, Oregon, have not developed white pine blister rust under natural conditions during the past 5 years. We wanted to find out if these plants were avoiding the disease - or were immune to it. We decided to spray a high level of spores (about 30,000 spores ml-1) on leaves of these plants to se if the disease would develop. After 3 weeks, 66 types of currants and gooseberries developed low level infections. These included several Jostaberries, Josta, Jostiki, and some Oregon hybrid selections; 28 black, 11 red, 4 whites and 11 gooseberries. During that same testing period, 44 of the currants and gooseberries developed no infection. These highly resistant types included 12 black, 5 red, 1 white currant, another Oregon hybrid selection, and 26 gooseberries. Of this last group 4 black currants sare known to have a specific gene for resistance. These cultivars, Consort, Coronet, Crusader, and Titania, do not develop rust in the field or after laboratory tests. Our tests confirmed that they are immune. The broad range of species and origins of the highly resistant clones indicate that currants and gooseberries may have several genetic ways to prevent this disease from developing on their leaves.
Technical Abstract: White pine blister rust (Cronartium ribicola C.J. Fischer) resistance has been routinely observed in field-grown Ribes at the National Clonal Germplasm Repository in Corvallis, Oregon, since 1995. Rust uredia do not form on some black currant (R. nigrum L.), red currant (R. rubrum) or gooseberry (R. uva-crispa L.) genotypes following natural exposure to inoculum. The objective of this study was to determine if uredia would develop on these resistant genotypes after artificial inoculation. Uredinial rust spores were gathered from infected black currants leaves in the Corvallis field planting. In August 2000, an agar-water suspension of inoculum was prepared containing about 30,000 spores ml-1. About 2 ml of the suspension was sprayed on each of 2 mature leaves from 2 plants for each of the 110 clones. After three weeks, 66 of the resistant clones deve loped low level infections. Jostaberries, including, R. x nidigrolaria Bauer cv. Josta, Jostiki, and all but one of the ORUS selections; 28 black 11 red, 4 white currants and 11 gooseberries developed less than 15 uredia per leaf on average. No uredia developed on 44 of the clones, including 12 black, 1 white currant, an ORUS selectoin, and 26 gooseberries. None of the black currant cultivars with the Cr gene for white pine blister rust immunity, i.e., Consort, Coronet, Crusder, or Titania, produced uredia. The broad range of species and origins of the highly resistant clones that did not develop uredia after artificial inoculation suggest that several genetic mechanisms for rust resistance may exist in Ribes.