ABSTRACT
Mentha x gracilis 'Variegata' is an ornamental clone with a phenotype caused by virus infection. Several clones were ordered from mail-order nurseries in an attempt to identify a virus consistently associated with symptoms. One of these clones did not exhibit typical 'Variegata' symptoms, and steps were taken to identify any agents causing the 'off-type' symptoms. One of the viruses identified in the atypical 'Variegata' clone is a previously unknown virus, a member of the family Flexiviridae. Sequence and phylogenetic analysis indicate that the virus, designated as mint virus-2, is related to members of the species Grapevine virus A, Grapevine virus B and Heracleum latent virus, placing it in the genus Vitivirus. A detection protocol for the virus has been developed, and the mint aphid (Ovatus crataegarius) was able to transmit the virus in the presence of a helper virus but not from single infected plants.
Subject(s)
Flexiviridae , Mentha/virology , Plant Diseases/virology , Animals , Aphids/virology , DNA Primers , Flexiviridae/classification , Flexiviridae/genetics , Flexiviridae/isolation & purification , Flexiviridae/physiology , Mentha/parasitology , Molecular Sequence Data , Phylogeny , Plant Leaves/virology , Polymerase Chain Reaction/methods , Sequence Analysis, DNAABSTRACT
Several clones of golden ginger mint (Mentha x gracilis, 'Variegata') were found infected with Strawberry latent ringspot virus (SLRSV). The virus was purified and cloned and the complete nucleotide sequence of a mint isolate was obtained. RNA 1 consists of 7,496 nucleotides excluding the poly-A tail and encodes a polyprotein with signature enzymatic motifs found in other picorna-like plant viruses. RNA 2 consists of 3,842 nucleotides excluding the poly-A tail, encoding a polyprotein that is processed to a putative movement protein and the two coat proteins of the virus. A satellite RNA of 1,117 nucleotides was associated with this isolate encoding for a putative protein of 31 kDa. Phylogenetic analysis revealed that SLRSV shares characteristics with members of the Cheravirus, Fabavirus, Comovirus and Sadwavirus genera indicative of the uniqueness of SLRSV. The close relationship of SLRSV with these genera led to the examination of aphid and beetle transmission of the virus with, however, negative results.
Subject(s)
Comovirus/genetics , Genome, Viral , Mentha/virology , Animals , Aphids , Biological Evolution , Coleoptera , Comovirus/classification , Insect Vectors , Molecular Weight , Plant Diseases/virology , Species Specificity , Viral Proteins/chemistry , Viral Proteins/geneticsABSTRACT
Mentha x gracilis 'Variegata', an ornamental mint clone first described about 200 years ago, exhibits virus-like vein banding symptoms. Double-stranded RNA and virion isolations revealed the presence of three viruses in a 'Variegata' plant. Cloning and sequencing disclosed that one of the viruses was a previously unidentified species with similarities to members of the Flexiviridae family, designated as Mint virus X (MVX). The complete nucleotide sequence of the virus was determined. Phylogenetic analysis divulged the close relationship of the virus with lily virus X and strawberry mild yellow edge virus, members of the Potexvirus genus. A reverse transcription-polymerase chain reaction protocol was developed and used for detection of MVX in other 'Variegata' plants. All clones tested, obtained from nurseries around the United States were infected with MVX, making the virus a possible causal agent of the variegated symptoms.