Birth of a Hyaloperonospora arabidopsidis (ex parasitica) isolate (Emoy2) and oomycete genomics in Arabidopsis thaliana. Emoy2 was germinated from a sexual oospore (DOB 18 June 1991) that infected a Columbia seedling via the root (far left photo) and colonized the hypocotyl and both cotyledons (hyphae shaded in blue, false color) before producing two sporangiophores (black arrow) bearing asexual conidiosporangia (middle photo). Four standard Arabidopsis accessions, Columbia (Col), Landsberg erecta (Ler), Niederzenz (Nd) and Wassilewskija (Ws), each exhibit resistant phenotypes following the infection of cotyledons with Emoy2 (far right photo). These phenotypes range from full resistance with no sporulation and a barely visible host response (top cotyledon), through patches of necrosis and no sporulation (second from top) and weak necrosis that trails behind the hyphal growth of the parasite and partial sporulation (third from top), to full susceptibility (bottom cotyledon). Downy mildew resistance genes (RPP, for recognition of Peronospora parasitica) that confer these different phenotypes have been characterized molecularly.
Via Kamoun Lab @ TSL