Tasmanian Institute of Agriculture (TIA), University of Tasmania, New Town, Tasmania 7008, Australia.
TIA, University of Tasmania, Burnie TAS 7320, Australia.
Plant Dis. 2018 Nov;102(11):2277-2284. doi: 10.1094/PDIS-03-18-0503-RE. Epub 2018 Sep 13.
Downy mildew is a serious threat to opium poppy production globally. In recent years, two pathogen species, Peronospora somniferi and Peronospora meconopsidis, which induce distinct symptoms, have been confirmed in Australia. In order to manage the spread of these pathogens, identifying the sources of inoculum is essential. In this study, we assessed pathogen presence associated with poppy seed. We developed PCR and qPCR assays targeting the coxI and coxII gene regions, for the detection, differentiation, and quantification of P. somniferi and P. meconopsidis in poppy seed. These results were complemented and compared with direct seed histological examination and a seed washing combined with viability staining for oospore detection. The majority of seed lots from all harvest years contained detectable P. meconopsidis, the earliest (1987) predating the first official record of the disease in Tasmania (1996). In contrast, only seed lots harvested in 2012 or later contained P. somniferi, evidence of its more recent introduction. P. meconopsidis contamination was estimated to be as high as 33.04 pg DNA/g of seed and P. somniferi as high as 35.17 pg DNA/g of seed. Incidence of pathogen contamination of seeds, estimated via a group testing protocol, ranged from 0 to 9% (P. meconopsidis) or 0 to 11% (P. somniferi). Mycelia were predominately found external to the seed coat. Seed washing and viability staining demonstrated that putatively viable oospores were present in the majority of seed lots. Transmission testing confirmed both pathogens can be successfully transmitted from infested seed to infected seedling. PCR and qPCR pathogen assays were found to be reliable and offer a routine test for determining pathogen inoculum in poppy seeds.
霜霉病是全球罂粟生产的严重威胁。近年来，在澳大利亚已确认两种引起不同症状的病原菌种，即罂粟霜霉病菌和罂粟疫霉病菌。为了管理这些病原体的传播，确定接种体的来源至关重要。在这项研究中，我们评估了与罂粟种子相关的病原体存在情况。我们开发了针对 coxI 和 coxII 基因区域的 PCR 和 qPCR 检测方法，用于检测、区分和定量罂粟种子中的罂粟霜霉病菌和罂粟疫霉病菌。这些结果与直接种子组织学检查以及种子清洗与活力染色相结合检测卵孢子的方法进行了补充和比较。所有收获年份的种子批次中，大多数都含有可检测到的罂粟疫霉病菌，最早的批次（1987 年）早于塔斯马尼亚州（1996 年）首次官方记录该疾病的时间。相比之下，只有在 2012 年或之后收获的种子批次才含有罂粟霜霉病菌，表明其是最近传入的。估计罂粟疫霉病菌的污染高达 33.04 pg DNA/g 种子，而罂粟霜霉病菌的污染高达 35.17 pg DNA/g 种子。通过群组测试方案估计，种子中病原体污染的发生率从 0 到 9%（罂粟疫霉病菌）或 0 到 11%（罂粟霜霉病菌）不等。菌丝主要存在于种皮外部。种子清洗和活力染色表明，大多数种子批次中都存在推定的有活力卵孢子。传播测试证实，受感染的种子可以成功将两种病原体传播到感染的幼苗。PCR 和 qPCR 病原体检测方法被发现是可靠的，并且为确定罂粟种子中的病原体接种体提供了常规检测方法。
