Invasive Species Compendium

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Abstract

A new Tobamovirus infecting Hoya spp.

Abstract

During 2019-20, a batch of 6000 young plants of different Hoya spp. was grown in a nursery in Germany. The plants had been originally imported from Thailand and a large proportion developed symptoms consistent with viral infection, e.g. ringspots, necrotic lesions, and irregular chlorosis or chlorotic leaf spots. The plants were analyzed by electron microscopy and non-enveloped rod-shaped particles were observed, suggesting infection with a Tobamovirus. Total RNA was extracted from infected leaf material and a generic Tobamovirus RT-PCR was performed using the Tob-Uni 1 and Tob-Uni 2 primers. The sequences showed 69.4% nucleotide (nt) identity to Hoya chlorotic spot virus (HoCSV; KX434725) indicating the presence of a novel tobamovirus, provisionally named Hoya tobamovirus 2 (HoToV2). Two of the samples (JKI2001336 and JKI2001337) were sequenced using MinION sequencing. In sample JKI2001336, HoToV2 was detected whilst in sample JKI2001337, HoToV2 and Tomato spotted wilt virus were detected in a mixed infection. Pairwise alignment using Clustal Omega (1.2.2) showed that the amino acid (aa) sequences of the movement protein (MP) of the two isolates of HoToV2 share 99.7% aa identity to each other and 52.3% identity to HoCSV. The coat protein sequences of the two isolates are identical and share 67.3% aa identity to HoCSV. Phylogenetic analyses grouped both proteins within the tobamovirus genus close to HoCSV. Based on the current results, HoToV2 is proposed as a new species within the genus Tobamovirus, family Virgaviridae.