Potential susceptibility of Australian native plant species to branch dieback and bole canker diseases caused by Phytophthora ramorum

Susceptibility to branch dieback caused by Phytophthora ramorum was tested using a detached branch assay for 66 Australian native plant species sourced from established gardens and arboreta in California. Six of these species were further tested for their susceptibility to bole cankers caused by P. ramorum using a sealed log assay. Isopogon formosus and Eucalyptus denticulata were identified as potentially highly susceptible Australian branch dieback hosts. Thirteen potentially tolerant Australian host species included Banksia attenuata, B. marginata, E. haemastoma, E. regnans, Pittosporum undulatum and Billardiera heterophylla. Eucalyptus regnans was identified as a potentially highly susceptible bole canker host, while E. diversicolor and E. viminalis were considered potentially tolerant species to bole cankers caused by P. ramorum. Phytophthora ramorum was able to infect all 66 species, as confirmed by reisolation. These results extend the known potential host range for P. ramorum, confirm it as a possible threat to Australian plant industries and ecosystems and highlight additional associated hosts that are important in the global horticultural trade, native forests and plantation forestry.     

栎树猝死病菌检疫鉴定方法

根据栎树猝死病菌的形态学、生物学培养性状和分子生物学等方面的特征，确立了检疫鉴定栎树猝死病菌的各项技术要求。     

Phytophthora ramorum and Phytophthora kernoviae on naturally infected asymptomatic foliage

Phytophthora ramorum and Phytophthora kernoviae are recently discovered invasive Phytophthoras causing leaf necrosis and shoot tip dieback mostly on ornamental and forest understorey species, but also cause bleeding cankers on stems of a wide range of tree species. Sporulation occurs only on infected shoots or fruits and foliage so foliar hosts are central to the disease epidemiology. In field trials to assess infection in trap plants exposed to natural inoculum of P. ramorum and P. kernoviae on rhododendron in south west England, it was discovered that leaves of the trap plants ( Rhododendron 'Cunninghams White') and holm oak ( Quercus ilex ) were asymptomatically infected and supported sporulation of both pathogens. More than half the rhododendron trap plants exposed to inoculum of P. kernoviae became infected compared with approximately a third of those exposed to P. ramorum in a natural situation. Approximately one third of the infections were detected from asymptomatic foliage for both pathogens. The significance of these findings for plant health regulation based on visual inspection as a measure to prevent introduction and dissemination of both these pathogens is explored and research gaps identified.     

First report of Phytophthora blight of celery (Apium graveolens var. dulce) caused by Phytophthora tentaculata in Japan

Journal of General Plant Pathology - A new disease on celery discovered in Japan caused extreme stunting, dwarfed and yellowed leaves, black rot of the celery “heart”, and root rot. A...