First Report of Groundnut bud necrosis virus in Tomato in Bangladesh

Abstract

An unusual disease of tomato characterized by leaf mottling and necrotic streaks on veins, shortened internodes, necrosis of terminal buds, and concentric rings on fruits was observed during 2010 to 2011 surveys in tomato growing regions of Godagari Upzila, Rajshahi district, Bangladesh. Disease incidence in popularly grown F1 hybrid cultivars, which include Sobal, Abhiruchi, Salamat, Bangobir, and BARI hybrid tomato-5 and -6 in about 40 commercial fields, ranged from 40 to 90%. Extracts from the field samples (n = 10) reacted with polyclonal antiserum to Groundnut bud necrosis virus (GBNV) in direct antigen coated ELISA, suggesting the association of a tospovirus antigenically related to serogroup IV topsovirus (1). To identify whether the tospovirus was a distinct virus species, ELISA-positive samples were subjected to total RNA extraction with an RNeasy Plant Mini Kit (Qiagen, Chatsworth, CA) followed by reverse transcription (RT)-PCR with tospovirus-specific primers (5′-ATGGTTGAAAAGAGCAAGAATGATGC-3′) and degenerate primer (5′-CTTCTTATGAAGTGTACTCACCATAAGTCATCC-3′) derived from the conserved sequences of GBNV, Watermelon bud necrosis virus (WBNV), and Capsicum chlorosis virus (CaCV) (2). The RT-PCR product was cloned into pGEM-T Easy vector (Promega, Madison, WI) and sequenced at Department of Biochemistry, University of Delhi, South Campus, Delhi, India (GenBank Accession No. JQ692083). The sequences of cloned fragments were assembled. Analysis of the 477-bp region of the nucleocapsid protein (N) gene revealed that the tomato tospovirus shared maximum identity both at the nucleotide (96%) and amino acid (97%) levels with the corresponding region of GBNV. In contrast, only 78 to 81% and 85 to 87% identity at nucleotide and amino acid levels, respectively, was observed with the corresponding region of the N genes of CaCV, WBNV, and Watermelon silver mottle virus. These results suggested the association of GBNV with the diseased tomato samples. To our knowledge, this is the first report of GBNV infecting tomato in Bangladesh and regular surveys are necessary to ascertain the prevalence and incidence of GBNV in other crops. References: (1) R. K. Jain et al. J. Virol. Methods 130:162, 2005. (2) M. Tsompana and J. W. Moyer. Tospovirus. Page 157 in: Encyclopedia of Virology. Academic Press, New York, 2009.