Archivio Journal of Plant Pathology

Abstract:

Guar (Cyamopsis tetragonoloba), family Fabaceae, is a drought-tolerant annual legume crop known as cluster bean, grown in tropical and sub tropical regions of the world. In India 1.93 million tonnes are produced on a surface of 3.86 million ha. Guar is extensively used by paper, mining, food, cosmetic, textile, oil and pharmaceutical industries (Hymowitz and Matlock, 1963). In November 2011, foliar mosaic and necrotic spotting as well as necrotic streaks on buds and stems were observed in guar fields of Chittoor district of Andhra Pradesh (India). Based on symptomatology, infections by Tobacco streak virus (TSV) a mem- ber of the genus Ilarvirus, family Bromoviridae were suspected. The presence of the virus was confirmed in symptomatic leaves by direct antigen coating (DAC)-ELISA using TSV polyclonal antibodies. RT-PCR amplification using as template total RNA isolated from leaf tissue and primers specific for the coat protein gene of TSV (Bhat et al., 2002) resulted in an amplicon of the ex- pected size (ca. 700 bp). The PCR product was cloned into pTZ57R/T vector (Fermentas, USA) and sequenced (GenBank accession No. JQ269831). Sequence analysis (BioEdit v. 7.05) dis- closed 98.8-99.8% and 97.8-100% identity at the nucleotide and amino acid levels, respectively, with the coat protein gene of 16 other TSV isolates. Phylogenetic trees constructed using MEGA version 4.0, showed clustering of the TSV isolate from guar with another isolate from sun-hemp (AF515825). To the best of our knowledge this is the first report of the natural occurrence of TSV on guar.