First report of Pea necrotic yellow dwarf virus in The Netherlands

Pea necrotic yellow dwarf virus (PNYDV) is a nanovirus that was first detected in pea crops (Pisum sativum) in Saxony-Anhalt, Germany in 2009 (Grigoras et al., 2010). In 2016, PNYDV was detected countrywide in both Germany and Austria not only on pea but also on faba bean (Vicia faba), vetch (V. sativa) and lentil (Lens culinaris) causing severe yield losses (Gaafar et al., 2016).

During a routine survey of twelve green pea crops in the Province of Flevoland (The Netherlands), plants with virus-like symptoms were noticed (Fig. 1). Symptomatic plant material was pooled from each field and analysed by ELISA for typical pea viruses: Alfalfa mosaic virus, Cucumber mosaic virus, luteo-/poleroviruses, Pea enation mosaic virus (PEMV), potyviruses, and Red clover vein mosaic virus-like carlaviruses, and nanoviruses. PEMV was detected in all fields while luteo-/poleroviruses were found in one field. Two samples each from different pea fields reacted positively using a broad nanovirus monoclonal antibody mixture (Gaafar et al., 2016). The lack of reaction with a monoclonal antibody mixture designed to detect only Faba bean necrotic stunt virus and Faba bean necrotic yellows virus suggested infection with Pea necrotic yellow dwarf virus (PNYDV). This was confirmed by PCR using PNYDV-specific primers targeting the eight PNYDV components producing bands of approximately 1 kb (Table 1). All PCR products were cloned using the NEB PCR cloning kit (New England Biolabs, Germany) and at least four clones for each component were sequenced in both directions. The sequences of the eight components of the two Dutch isolates (NL HZ16-186 and NL HZ16-189) had between 96.7 and 99.9% identity with the equivalent PNYDV components of an isolate from Germany and between 96.7 and 99.8% with an Austrian isolate (Table 1). The sequences of the Dutch PNYDV isolates have been deposited in GenBank (KY593279- KY593294).

To our knowledge, this is the first report of PNYDV in The Netherlands. This indicates that nanoviruses are far more spread throughout Europe than previously thought (Grigoras et al., 2014). As PNYDV is aphid-transmitted in a circulative, non-propagative manner, it is expected that more nanovirus diseases will occur in the future as changes in climatic conditions (especially milder winters in Central Europe) favour aphid survival thus facilitating the spread of these viruses (Ziebell, 2017).