Epidemiology of barley yellow dwarf and wheat dwarf diseases

The most important cereal viruses are Barley/Cereal yellow dwarf virus (B/CYDV, genera Luteovirus/Polerovirus, family Luteoviridae) and Wheat dwarf virus (WDV, genus Mastrevirus, family Geminiviridae). B/CYDV is a complex of at least nine viral species and WDV consists of two main strains. B/CYDV and WDV are exclusively transmitted by aphids and leafhoppers, respectively. In spite of a wealth of data on both B/CYDV and WDV pathosystems, little information is available processes related to (i) the emergence, spread and maintenance of these viruses in a landscape including cultivated and wild compartments and (ii) the interactions between these viral species and between their vectors. An intensive survey was conducted to collect plants and insects in a 5 km² landscape (Annoix, Cher, France) where B/CYDV and WDV, and their vectors (i.e. cereal aphids and Psammotettix alienus), are usually highly prevalent. Previously characterized and putative host species of the Poaceae family present in the visited areas were sampled. Simultaneously, aphids and leafhoppers were caught using yellow water traps and sticky traps. The presence of BYDV-PAV, BYDV-MAV, CYDV-RPV and WDV in collected plants and insects was assessed using serological and molecular tools. A total of 37 wild gramineous species were identified. Serological analyses revealed that B/CYDV was present in 9 wild gramineous species.Surprisingly, none of the thousands collected leaves were infected by WDV. To complement the description of the gramineous species present in the studied landscape and their possible role as viral reservoirs (Abt et al., 2017), interactions between viruses and between vectors with overlapping host ranges will be analyzed in order to determine (i) how these pathogens (and their vectors) compete for host resources and (ii) the consequences of such interactions on the epidemiology of barley yellow dwarf and wheat dwarf diseases.