First Report of Blueberry scorch virus on Highbush Blueberry in Connecticut and Massachusetts.

Abstract

During June and July 2001, the Marucci Center received 33 foliage samples from healthy- and unhealthy-looking highbush blueberry (Vaccinium corymbosum L.) bushes from growers in Connecticut and Massachusetts, via local extension agents. Unhealthy bushes were reported to exhibit symptoms including leaf chlorosis and necrosis, blossom blight, tip dieback, or a general decline in vigor. Marginal leaf chlorosis, reddening, or necrosis characterized foliage samples from these bushes. Five-leaf samples from each bush were tested for Blueberry scorch virus (BlScV) (3) with Agri-Check detection kits (Hydros, Inc., Falmouth, MA). These kits use an indirect enzyme-linked immunosorbent assay (ELISA) protocol and antibodies developed at Rutgers University that are specific to the two eastern strains of BlScV (NJ1 and NJ2) (1). The ELISA extraction buffer was based on that used by Martin and Bristow (3) with 1% (wt/vol) nonfat dry milk powder added as a blocking agent. Fourteen samples from cvs. Blueray and Berkeley in both states and cvs. Elliott, Bluecrop, and Coville in Massachusetts tested positive for BlScV. These results were confirmed by a second test. Six of seven samples from symptomatic bushes and 8 of 26 samples from asymptomatic bushes harbored BlScV. Virus preparations extracted from five infected plants (two from Connecticut and three from Massachusetts) were examined using reverse transcription-polymerase chain reaction (RT-PCR) with oligonucleotide primers (5'-TGTGTCAAACAATATGGC-3' and 5'-GCATTTCGATGA-TTGCGG-3') designed to amplify a portion of the coat protein gene from any of the three known virus strains (1,2). Sequence analysis of fragments amplified from their coat protein genes revealed that two of the isolates from Massachusetts (GenBank Accession Nos. AY530957 and AY530958) and the two isolates from Connecticut (GenBank Accession Nos. AY530955 and AY530956) were similar but not identical to one another, and these four were most similar to strain NJ2. One isolate from Massachusetts (GenBank Accession No. AY530958) was most similar to strain NJ1. To our knowledge, this is the first report of BlScV on the east coast outside of New Jersey, where it was first reported in 1983 (4). These results indicate that the disease is now present in other blueberry-growing areas in the northeast and is likely to be spreading locally within those areas. Because blueberry scorch is symptomless in propagation material and may take several years to express symptoms in the field, the initial spread of the disease was probably due to the shipping of latently infected plants to BlScV-free areas before reliable testing was available.