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'.
P.J. Macdonald and Margie Luffman
A collection of indigenous North American red raspberry (Rubus strigosus Michx.) was evaluated in an unreplicated field planting at the Canadian Clonal Genebank, Trenton, Ont. The accessions originated in British Columbia (B.C.) and the United States. Useful characteristics in the collection have been identified under B.C. conditions; however, field performance in Ontario has not been reported. Cultivars originating from B.C., Manitoba, and Ontario were included in the planting as standards. Overwintering injury ranged from slight to severe. Indigenous accessions were vigorous, with cane height comparable to standards; however, in some cases, primocane production was excessive. Most B.C. accessions flowered and fruited equivalent to, or earlier than, the earliest cultivar (`Boyne'), while R. strigosus from other locations were mid-season to late. Primocane fruiting was typical in B.C., but was not consistent in Ontario. Fruit were small, but had good color and structure. Accessions showed resistance to powdery mildew [Sphaerotheca macularis (Wallr.:Fr.)], but were very susceptible to late yellow rust [Pucciniastrum americanum (Farl.) Arth.].
Philip L. Forsline, Margie Luffman, John Warner, and Leigh E. Towill
Based on protocols developed by the Plant Genetic Resources Unit (PGRU), Geneva, NY and the National Seed Storage Laboratory, Fort Collins, Colo., nearly 40% of the 2500-accession USDA–ARS Malus germplasm collection has been preserved cryogenically. Recent program changes require the entire Canadian Malus collection of 700 accessions at the Canadian Clonal Genebank, Trenton, Ont., be moved to a new location in Harrow, Ont., by the end of 1996. This provided an opportunity to utilize cryogenic storage during repropagation and reestablishment to develop a security backup for the collection. In a cooperative experiment, dormant buds of four Canadian Malus accessions were collected in Trenton and cryopreserved in Geneva in February 1995. Field-level moisture of dormant buds ranged from 45% to 50%. Three levels of bud desiccation were tested: 25%, 30% (current standard), and 35%. The desiccated buds were containerized and slowly frozen to –30°C, plunged into liquid nitrogen, and held for one month at Geneva prior to recovery testing by bud-grafting at Geneva and Trenton. Results were identical at both sites. We obtained 60% recovery at 30% and 35% moisture levels and 80% recovery at 25% moisture across all four accessions. Further studies on a broader range of germplasm will determine if desiccation to the 25% level is superior to the 30% level. Meanwhile, we have initiated a cooperative project to cryopreserve 350 accessions unique to the Canadian collection at Ft. Collins.