Alaskan Ribes L. and Rubus L. Plant Species Surveyed for Viruses

Authors: Robertson, Nancy; QUITO, DIEGO - Oregon State University; Martin, Robert

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2011
Publication Date: 4/30/2012
Citation: Robertson, N.L., Quito, D., Martin, R.R. 2012. Alaskan Ribes L. and Rubus L. Plant Species Surveyed for Viruses. Acta Horticulturae. 946:237-242.

Interpretive Summary: Currants, gooseberries, and raspberries are important berry plants that are grown in home gardens in Alaska. Similar types of berries also grow as native plant species in natural landscapes. These berries are used to make deserts, jams and jellies, drinks and may be sold at farmers markets. Identification of diseases and maintaining healthy plants is an important aspect of a productive berry crop. Virus diseases in the small fruits have not been examined and studied extensively in Alaska. In 2008, a plant disease survey was initiated on the Kenai Peninsula and in North Central Alaska with subsequent surveys through 2010. Diseased native raspberry growing in agricultural berms near North Pole, Alaska were determined to be infected with a plant virus of unknown taxonomical status. The leaves were mottled with light green and yellow discolorations. Commercial raspberry plants near infected native raspberries were not diseased. Another plant virus was discovered in black and red currants in a home garden near Sterling, Alaska. Affected currant plants contained leaves with discolored spots and vein-clearing. Based on biological and molecular criteria, the virus isolated from currant leaves was tentatively determined to be a new vitivirus. Propagation cuttings from virus infected currant and raspberry plants should be avoided to help prevent the spread of viruses. This is the first time that viruses have been detected in currants and raspberries from Alaska, and the first report of a vitivirus in currants.

Technical Abstract: Alaska’s domesticated and native Ribes and Rubus genera have virtually gone unchecked for pathogen detections. Cultivated Ribes species are predominantly found in home gardens and landscape areas along highways and in cities. In 2008, while surveying native plants for diseases in North Central Alaska near the town of North Pole, mottled leaves were readily visible on wild raspberries (Rubus strigogus L.) growing in agricultural berms and on recent clearings next to forests. In 2009 and 2010, other sites close to the original sites were observed to have similar symptoms. Initial protein extracts from partially purified preparations revealed a putative coat protein about 30 kDa. Mechanical transmission occurred in Nicotiana benthamiana and Chenopodium quinoa. Virion RNA preparations contained two dominant bands about 5.9 kb and 1.9 kb. Based on these biological parameters and similarities with Raspberry bushy dwarf virus, leaf sap and purified virion from infected raspberry and N. benthamiana were assayed for RBDV by ELISA and western blot. Leaf samples were also tested specifically for RBDV by RT-PCR. Negative results indicated that RBDV was not the causal agent involved in the native raspberry disease. Commercial raspberries growing near infected wild plants did not have symptoms and did not test positive for viruses. Another virus was discovered and detected from domesticated black and red currants (Ribes nigrum L. and R. rubrum L.) in 2008 and 2010 on the Kenai Peninsula, Alaska. Diseased plants usually contained leaves with vein-clearing that developed into large spots. Field collected leaf samples tested positive for vitivirus using a RT-PCR assay adapted for vitivirus detection. Direct sequencing of the ca. 200 bp PCR product resulted in nucleotides that were most similar to species in the genus Vitivirus when analyzed in BLAST. This is the first time that viruses have been detected in currants and raspberries from Alaska and the first report of a vitivirus in Ribes spp.