Poster Board 74. Determining Peronospora somniferi genotype diversity and its potential impact on management of systemic downy mildew of opium poppy

Opium poppy (Papaver somniferum) is grown for its pharmaceutically important opiates (1). Australian production comprises over 50% of the world’s licit production and is primarily based in Tasmania with limited production in mainland Australia. Outbreaks of a new systemic form of downy mildew (SDM) in 2014 raised significant industry concern (1). SDM infections were characterised by stunted and deformed plant growth, often leading to early plant death. Peronospora somniferi was identified as the causal organism of SDM (1). The level of diversity within Australian populations of P. somniferi is unknown. However, recently an isolate of P. somniferi that caused localized lesions rather than a typical systemic infection was noted. This suggests the presence of races in the P. somniferi population of Australia. To address this knowledge gap, simple sequence repeat (SSR) markers were developed following construction of a whole genome assembly of a P. somniferi individual using Illumina paired end reads. Repeats of tri- and quad- base pair motifs were targeted for further marker development. Primers were developed for screened SSR marker regions and sanger sequencing was used to confirm target region and marker polymorphism. Polymorphic SSR markers were tested against different field P. somniferi individuals to identify the level of diversity present, with marker fragments sized by capillary electrophoresis. The outcomes of this study will be presented at the meeting. Studies to examine potential links between pathogen genotype and host symptom response are planned to follow.