Viticulture, one of the most remunerative farming enterprises of India, is seriously affected by leafroll disease, which accounts for 62% of the losses in grape production worldwide due to viral diseases (4). Grapevine leafroll-associated virus 3 and 1 (GLRaV-3 and GLRaV-1) of the family Closteroviridae are the two most common viruses associated with the leafroll disease of grapevine (1). GLRaV-3 was previously confirmed in India through RT-PCR, cloning, and sequencing (2). A survey was conducted during 2010 and 2011 in the Nashik and Pune regions of western India and reddening of interveinal areas and downward rolling, typical symptoms of leafroll disease in dark fruited cultivars, were observed, first in 2010 and subsequently in 2011. Fourteen leafroll symptomatic samples from seven cultivars of seven vineyards were collected during 2011. Samples were subjected to double antibody sandwich (DAS)-ELISA using commercially available antibodies against GLRaV-3 and GLRaV-1 (Bioreba, Reinach, Switzerland) (2). An asymptomatic sample from another cultivar of a different vineyard and samples from two plantlets of two different cultivars produced in tissue culture were used as negative controls. GLRaV-1 was detected in two cultivars, Shiraj (Nashik region) and Pinot Noir (Pune region) using DAS-ELISA. GLRaV-1 was detected either alone in cultivar Pinot Noir or as mixed infection with GLRaV-3 in cultivar Shiraj. To further confirm the presence of GLRaV-1 in these two cultivars, crude extract from petioles of these two cultivars were subjected to one step reverse transcription (RT)-PCR using GLRaV-1 specific primers pORF9F and pORF9R (GGCTCGAGATGGCGTCACTTATACCTA and CCTCTAGACACCAAATTGCTAGCGA, respectively) (3). The ˜650 bp amplicons were cloned in pGEM-T easy vector and three independent clones of each amplicon were sequenced in both directions. The cloned amplified product was 646 bp, including 630 bp of p24 protein (ORF9) of GLRaV-1. Comparative sequence analysis, using the BioEdit 7.0.3 program (
http://www.mbio.ncsu.edu/BioEdit/BioEdit.html), of ORF9 of the virus under study from the cultivars Pinot Noir and Shiraj shared maximum sequence identity of 95.8 and 96.1%, respectively, at the nucleotide level with the Clatervine isolate from the United States (GenBank Accession No. HQ833477). The corresponding values of maximum identities at the amino acid level were 96.6 and 96.1%, respectively, with the same Clatervine isolate. The maximum identity between these two isolates of GLRaV-1 was 96.1% at nucleotide level and 95.7% at amino acid level. To the best of our knowledge, this study represents the first report of GLRaV-1 from India. Grape production in India could be impacted by this virus; thus, identification of the virus is important.
References: (1) B. Akbas et al. Hort. Sc. (Prague). 36: 97, 2009. (2) S. Kumar et al. Virus Genes. 45:195, 2012. (3) A. Little and M. A. Rezaian. Arch. Virol. 151:753, 2006. (4) A. Little et al. Virus Res. 80:109, 2001.
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