Canadian Forest Service Publications
Impact of white pine blister rust on resistant cultivated Ribes and neighboring eastern white pine in New Hampshire. 2015. Munck, I.A.; Tanguay, P.; Weimer, J.; Villani, S.M.; Cox, K.D. Plant Dis. 99:1374-1382.
Issued by: Laurentian Forestry Centre
Catalog ID: 36162
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To determine the impact of white pine blister rust (WPBR) following the recent breakdown of the Cr resistance dominant gene in Ribes, 255 plants of 19 Ribes cultivars and 445 neighboring eastern white pines (Pinus strobus) from 42 sites across New Hampshire were evaluated. Of the 19 cultivars evaluated, 15 were WPBR resistant, and four of these were labeled as black currants (R. nigrum) with the Cr gene (Cr Ribes cultivars). Incidence of WPBR ranged from 0% to 88% for WPBR resistant Ribes cultivars. Mean WPBR severity was 14% and < 6% of leaf area for Cr Ribes and partially resistant cultivars, respectively. The presence of C. ribicola was confirmed on 17 of the 19 Ribes cultivars screened with PCR analysis and DNA sequencing. Reference accessions of Cr Ribes cultivars from the Canadian Clonal Genebank were successfully infected with C. ribicola inoculum collected in New Hampshire from Cr Ribes cultivars and P. strobus confirming that the vCr race of the pathogen that has defeated the Cr dominant gene in cultivated Ribes is present in New Hampshire. The probability of finding pines with WPBR was greater for pines neighboring infected black currants with the Cr gene (0.18) than pines neighboring WPBR-free Ribes (0.02). Results from this study suggest that the breakdown of Cr-based resistance in Ribes poses a threat to the white pine resource and to cultivated Ribes production.
Plain Language Summary
In various areas of New Hampshire, the researchers identified white pine trees infected by a new race of white pine blister rust. They found that the likelihood of finding white pine trees infected with this disease was proportional to the distance separating them from Ribes (black currants and gooseberries). The closer the pine trees were to Ribes, the greater the chances were of their being infected with the disease.
The researchers also succeeded in infecting Ribes cultivars from the Canadian Clonal Genebank that had previously characterized as being immune to this disease. They did so by using samples of a new race of rust collected in New Hampshire. This confirms that the new race of rust, which overcame the resistance of the resistant Ribes cultivars, is present in New Hampshire.
White pine blister rust is a disease caused by an exotic fungus that spends part of its life cycle on Ribes before attacking white pine trees in the forest. For more than 50 years, farmers had access to black currant cultivars that were immune to white pine blister rust, which reduced the impact of this disease on nearby white pine trees. However, in 2008, loss of black currant immunity was observed in Connecticut. In 2011 and 2013, a new virulent race of white pine blister rust was sampled and observed in Quebec, in the Maritime provinces, and in several states in the northeastern United States.