Biological and molecular characterisation of the two Polish Wheat streak mosaic virus isolates and their transmission by wheat curl mites

Wheat streak mosaic virus (WSMV) is a serious and widespread pathogen in the wheat-producing areas in the USA while, in Europe, it has been considered a minor threat to cereal crops. In the past, WSMV was detected in wheat, triticale and maize plants in Poland by DAS-ELISA. Here, we present the biological and molecular characterisation of WSMV-Sze and WSMV-Sosn isolates collected from western and southern Poland and report their transmissibility by the widespread wheat curl mite (WCM) lineage MT-8. The performed bioassays revealed that the analysed WSMV isolates infect wheat, barley, triticale, rye, oat and maize, but they differ in the symptoms induced on the infected plants. Moreover, they infect Bromus hordeaceus Linnaeus, which is increasingly recognised as a virus reservoir. The full-length genome sequence of both isolates was obtained and compared with the others described to date. The phylogenetic analysis revealed that the Polish isolates are clustered with the earlier described type B isolates of WSMV from Europe and Iran. The recombination analysis revealed the presence of recombinant variants in WSMV population and indicated that the WSMV-Sosn might originated from the intra-species recombination of the WSMV-Sze and WSMV-Cz isolates.