Capsicum chlorosis virus (Genus Tospovirus) Infecting Chili Pepper (Capsicum annuum) in India.

Abstract

Chili pepper (Capsicum annuum L.) is one of the most important spice crops in India. In October of 2006, symptoms indicative of tospovirus infection were noticed in several commercial fields of chili pepper near Bangalore in Karnataka State. Chlorotic and necrotic spots and rings on leaves, apical necrosis, and leaf distortion were observed. Disease incidence was more than 20%. Mechanical inoculation with sap extracts from these symptomatic plants showed that the host range and symptomatology of the virus was similar to those described for Capsicum chlorosis virus (CaCV) (1,3). The virus reacted with antisera specific to Groundnut bud necrosis virus (GBNV) and Watermelon silver mottle virus of serogroup IV tospoviruses in antigen-coated plate ELISA. It did not react with antisera specific to Tomato spotted wilt virus, Impatiens necrotic spot virus, or Iris yellow spot virus in double-antibody sandwich-ELISA. Immunosorbent electron microscopy of infected sap using GBNV antiserum revealed the presence of strongly decorated quasi-spherical virus particles. Reverse transcription (RT)-PCR was conducted to further identify the virus. No amplification was observed from extracts of symptomatic plants (n = 10) by RT-PCR using GBNV-specific primers (4), indicating that the diseased chili was not infected with GBNV. However, a DNA fragment of approximately 850 bp was amplified by using primers specific to the nucleocapsid (N) gene of CaCV (CaCF 5'-CTATAGAWGTACTAGGCTTTGAGC-3' and CaCR 5'-CATGTCTAACGTCAGGCAACTTAC-3'). Direct sequencing of the amplicon (GenBank Accession No. EF625227) revealed a nucleotide sequence identity ranging from 85.5% with isolates from Thailand (GenBank Accession Nos. AY846366, AY647437, and AF134400) and China (GenBank Accession No. DQ355974) to 98.1% with isolates from Australia (GenBank Accession Nos. AY036057 and AY036058). Phylogenetic analysis of the N protein sequences showed that the chili pepper isolate from India formed a cluster with those from Australia. This cluster was distinct from the one formed by the peanut isolates from Thailand and a tomato isolate from India (2). To our knowledge, this is the first report of CaCV infection of chili pepper in India. The potential impact of CaCV on tomato and chili pepper production in India remains to be seen.