Molecular identification and characterization of groundnut bud necrosis virus and its associated thrips vector from Gerbera jamesonii in India

Abstract

Gerbera is an important cut flower crop popular throughout the world. In summer months of 2016, gerberas grown in polyhouses of RHREC, GKVK, Bengaluru, Karnataka, India showed heavy infestation of thrips and displayed symptoms of viral infections. Infected plants displayed irregular chlorotic or necrotic spots or blotches, necrosis of veins, bronzing, crinkling and deformations of leaves; necrotic streaks on flower stalks; chlorosis or necrosis of flower petals; tip necrosis or death of young plants. The virus was identified as groundnut bud necrosis virus based on DAC-ELISA, RT-PCR and transmission studies, and it was characterized by cloning and sequencing of N gene and 3′ UTRs. Thrips associated was identified as Scirtothrips dorsalis and the virus was detected in individual thrips using DAC-ELISA. The virus could be efficiently transmitted to cowpea variety C-152 both by mechanical sap inoculation and vector transmission and to tulsi plants by vector transmission. Sequence of S-RNA segment of the virus from two independent gerbera samples was submitted under the accession numbers KX832986.1 and KX832987.1. The two isolates showed per cent identities of 97.1 and 98.5 at N gene and at 3′ UTRs, respectively, with each other and 92.9–99.1% at N gene with other GBNV isolates. Phylogenetically they clustered along with other GBNV isolates reported from different hosts and locations within the major clade of watermelon silver mottle virus serogroup. Differential response was observed in gerbera varieties with respect to incidence of GBNV disease (19.6–80.6%) and thrips (24.6–54.0 thrips/leaf) with the least incidence in the varieties Esmara and Orinaco.