Occurrence and molecular characterization of Impatiens necrotic spot tospovirus in ornamentals in Serbia

Abstract

A subset of ornamentals grown in Serbia were surveyed for the presence of impatiens necrotic spot tospovirus (INSV) from 2008 to 2018. Out of 1578 samples tested for the presence of the virus using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), INSV was detected in 26 Begonia sp. and four Tulipa sp. samples collected in 2008 and in 10 samples of each of Begonia sp., Impatiens walleriana and I. hawkeri 'SunPatiens' and 'New Guinea' collected in 2018. INSV was not detected in any samples collected during 2009-2017. For further confirmation, the nucleotide sequence of the INSV nucleocapsid (N) gene was obtained by reverse transcription polymerase chain reaction (RT-PCR) in two and four samples collected in 2008 and 2018, respectively. The success of mechanical transmission of INSV isolates from different hosts was variable depending on isolates. Serbian INSV isolates showed very low nucleotide diversity and they were closely related to the Chinese and Japanese isolates already reported in the literature, indicating that the Serbian isolates might be of Asian origin. Phylogenetic analysis and the median-joining haplotype network of the N gene sequences showed clustering of Serbian INSV isolates in the Asian clade into two different subclades with different recent common ancestors implying two independent introductions. The sporadic occurrence of INSV with high temporal distance is a likely consequence of virus spread through the international trade in ornamental planting material. Therefore, the establishment of the virus should be considered and prevented when introducing new plant material into the country. This is also the first report of the tulip as a natural host of INSV.