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

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 strigosus 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 from Ribes spp. INTRODUCTION People living in Alaska have cultivated raspberries (Rubus L.), currants, and gooseberries (Ribes L.) since the arrival of the first settlers from Russia in the mid-1700s. Today, production of small fruits is limited to home gardens or small plots and the fruit is sold at local farm markets. Since virus diseases of small fruits in Alaska have not been examined, surveys were initiated in July 2008. In North Central Alaska, near North Pole, numerous wild raspberry (Rubus strigosus L.) plants growing on agricultural berms contained leaves with noticeable light green/yellow mottle (Fig. 1) accompanied with occasional curling and blistering. Another virus-like disease was discovered in domesticated currants (Ribes L.) from a home garden on the Kenai Peninsula near Sterling, Alaska. Leaf symptoms consisted of mosaic with chlorotic spots and veinclearing (Fig. 3). The aim of this research was to isolate and identify the putative viruses from the two described virus-like diseases in currant and raspberry plants, respectively. Proc. X Intl. Rubus and Ribes Symp.