Molecular characterization of tospoviruses infecting Capsicum annuum L.

Abstract

Chilli (<em>Capsicum annuum</em> L) a prime vegetable cum spice crop is infected by tospoviruses, which has become a serious threat to it's cultivation worldwide. A survey was conducted for infection of tospoviruses on the basis of chlorotic and necrotic symptoms in chilli growing areas of Tamil Nadu. The symptomatic leaves were positive for tospovirus-specific antiserum tested through direct antigen coating - enzyme linked immunosorbent assay (DAC-ELISA), dot blot immunobinding assay (DIBA) and tissue blot immunobinding assay (TIBA). The samples with typical symptoms were successfully established for the chlorotic and necrotic lesions in assay host, cowpea and chilli upon artificial inoculation of tospoviruses. Further, an expected complementary DNA (cDNA) fragment sequence of about 840 bp and 1.2 kb were positively amplified using PCR correspond to coat protein (CP) gene of the respective viruses, which confirmed the presence of groundnut bud necrosis virus (GBNV), capsicum chlorosis virus (CaCV) in chilli. However, there is a lack of standard method to understand the genetic information of tospoviruses infecting chilli which requires the reliable, sensitive and specific method. To address this issue, we have investigated an application based on CP gene of GBNV and CaCV to perform molecular profiling. The nucleotide sequences of GBNV and CaCV showed maximum identity between the isolates and amino acid sequences had more than 90% similarity. However, superimposed 3D prediction structures constructed using MODELLER software revealed the single variation at 259^th position comprising of glutamine and valine respectively. The protein profiling of CP gene provides the basic knowledge on properties of CP proteins of two tospoviruses infecting chilli and their structural relationships.