BLACKBERRY YELLOW VEIN ASSOCIATED VIRUS: A NEW CRINIVIRUS FOUND IN BLACKBERRY

Abstract

During the last three years blackberries in southern and southeastern U.S. have shown symptoms of vein clearing, yellow mottling and plant decline with considerable variation in symptoms with cultivars. We isolated dsRNA from symptomatic plants and identified high molecular weight bands similar to those isolated from plants infected with criniviruses. Paired extractions from virus-tested blackberries did not yield any dsRNA bands with molecular weight greater than 500 bp. Using degenerate primers developed against the crinivirus 1b protein in RTPCR resulted in an amplicon that when sequenced showed the virus was a member of the Crinivirus genus. We have also cloned the virus and sequenced clones containing regions of the minor coat protein of the virus. Phylogenetic analysis revealed that the new virus, designated as Blackberry yellow vein associated virus (BYVaV), is related most closely to Beet pseudo-yellows virus and Strawberry pallidosis associated virus, two criniviruses recently identified in strawberry. INTRODUCTION Symptoms of vein clearing, yellow mottling, ringspots and plant decline have been observed in blackberry in South Carolina, North Carolina and Arkansas over the past few years (Fig. 1). Initially the symptoms were thought to be caused by Tobacco ringspot virus (TRSV) as this virus is known to infect blackberry and similar symptoms attributed to TRSV infection have been reported (1). Symptomatic plants were tested for 14 viruses by ELISA including: Alfalfa mosaic, Arabis mosaic, Cucumber mosaic, Impatiens necrotic spot, Prunus necrotic ringspot, Raspberry bushy dwarf, Raspberry ringspot, Strawberry latent ringspot, Strawberry mild yellow edge, Tobacco ringspot, Tobacco streak, Tomato ringspot, and Tomato spotted wilt viruses as well as for Potyviruses using group specific antibodies. However, in ELISA tests very few plants that exhibited these symptoms tested positive for TRSV or any other virus. In this report we describe a crinivirus associated with the symptoms observed in blackberry and a reverse-transcritase polymerase chain reaction (RT-PCR) method for detecting this new virus. MATERIALS AND METHODS In an attempt to determine if there may be a new virus associated with these symptoms dsRNA was extracted from symptomatic and asymptomatic plants using a shortened version of the standard extraction method (2). After the dsRNA was bound to the cellulose powder in the presence of 16% ethanol in STE buffer, the samples were centrifuged for three minutes at 5,000 X g, the pellet was washed once with 50 ml of STE-EtOH and the cellulose repelleted by centrifugation. Two ml of STE was added to the final pellet and incubated at room temp for 5 min. The sample was then transferred to a microfuge tube and pellet at max rpm for 3 min. The supernatant was collected and nucleic acid precipitated by the addition of 2 ml of 95% EtOH with 5% 3 M sodium acetate. Samples were mixed then stored at -80C for 20 minutes before centrifugation in a microfuge at max speed for 30 minutes. Pellets were resuspend in 10 mM Tris-HCl containing 1 mM EDTA and analyzed by gel electrophoresis. Proc. X IS on Small Fruit Virus Diseases