Blueberry scorch virus Detected on Blueberry Plants Imported Into China

Abstract

Blueberry scorch virus (BlScV), a member of the Carlavirus genus in the Betaflexiviridae family, was first reported in the United States. Scorch caused by BlScV is a serious disease of blueberry and can lead to great loss of yield. At present, the disease has also been reported in Germany, Canada, Italy, and the Netherlands (Ciuffo et al. 2005; Kalinowska et al. 2013; Wegener and Punja 2004). However, the disease had never been reported on blueberry in China. Symptoms caused by BlScV range from asymptomatic to severe blighting of flowers and leaves depending on blueberry cultivars and virus strain. In 2015, 57 imported samples of highbush blueberry cultivars showing virus-like symptoms in an isolated blueberry orchard in Fujian Province (south China) were collected and tested for BlScV by DAS-ELISA using specific antiserum according to the manufacturer’s protocol (Agdia, U.S.A.). Among the samples, one was positive for BlScV in DAS-ELISA. To confirm the presence of the virus, RT-PCR was performed using BlScV-specific primers. A set of BlScV-specific primers, forward primer (5′-CTCAAGCCGCAGCGTCACA-3′) and reverse primer (5′-CACCAGTGTACTCCGTTTCGAGA-3′), was designed to amplify a 667-bp fragment of the coat protein gene of BlScV. Total RNA was extracted from the extracts of ELISA-positive sample using an RNA extraction kit (Qiagen, Germany). The first-strand cDNA was synthesized using cDNA synthesis kit (Promega, U.S.A.) according to the manufacturer’s instructions with the N6 random primer (Promega, U.S.A.). PCR was carried out using GoTaq Master Mix following the manufacturer’s protocol (Promega, U.S.A.). The program used for PCR amplification was 94°C for 3 min, followed by 35 cycles at 94°C for 30 s, 53°C for 30 s, and 72°C for 1 min, followed by a final extension at 72°C for 10 min. The expected 667-bp fragment was purified, ligated to pGEM-T easy vector (Takara, Japan), and sequenced. The obtained sequence was deposited in GenBank (accession no. KX977562) and analyzed. Further sequence comparison revealed that the amplicon nucleotide sequence was 97.6% identical to the sequence of an isolate of BlScV from the United States (KP232989), which confirmed the presence of BlScV. To our knowledge, this is the first report of BlScV in blueberries in China. In recent years, a number of blueberry cultivars from abroad have been introduced to China, and thus BlScV-infected blueberry has the potential to be an important long-distance vector. Considering that BlScV could become an important threat to blueberry production, all the imported blueberry bushes in the orchard were destroyed to prevent the spread of the virus.