TY - JOUR T1 - Dieback and mortality of Nothofagus in Britain: ecology, pathogenicity and sporulation potential of the causal agent Phytophthora pseudosyringae JF - Plant Pathology Y1 - 2016 A1 - Scanu, B. A1 - Webber, J. F. AB -

Since 2009 extensive dieback and mortality of Nothofagus obliqua, associated with bleeding cankers on stems and branches, has been observed in the UK. The causal agent was identified as Phytophthora pseudosyringae, based on morphological and analysis of the internal transcribed spacer (ITS) sequences. Between 2011 and 2013, a survey assessed the frequency and nature of these P. pseudosyringae infections. Mature trees of Nothofagus with stem lesions caused by P. pseudosyringae were found across England, Scotland and Wales. Additional symptoms such as twig blight and leaf necrosis indicated that aerial infection was occurring. Besides N. obliqua, other hosts regularly encountered included Nothofagus alpina, Fagus sylvatica and Vaccinium myrtillus. In pathogenicity tests involving inoculation of logs, P. pseudosyringae was shown to be an aggressive bark pathogen of N. obliqua and F. sylvatica, but significantly less aggressive on N. alpina. Foliage susceptibility and sporulation tests showed marked differences between the six host species tested. Leaves of N. obliqua and V. myrtillus were highly susceptible. Leaves of N. alpina were moderately susceptible, those of Rhododendron ponticum slightly susceptible and those of F. sylvatica not susceptible at all. High levels of sporulation were observed only on inoculated N. obliqua and V. myrtillus leaves. This suggests that P. pseudosyringae may sporulate heavily on N. obliqua foliage in the field and that this inoculum initiates the aerial lesions observed on the shoots, branches and stems. The results also suggest that P. pseudosyringae has the potential to pose a serious threat to N. obliqua and other Nothofagus species in their Southern Hemisphere native ranges.

VL - 65 UR - http://doi.wiley.com/10.1111/ppa.12399http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fppa.12399 IS - 1 JO - Plant Pathol ER - TY - JOUR T1 - A taxonomic re-evaluation reveals that Phytophthora cinnamomi and P. cinnamomi var. parvispora are separate species JF - Forest Pathology Y1 - 2013 A1 - Scanu, B. A1 - Hunter, G. C. A1 - Linaldeddu, B. T. A1 - Franceschini, A. A1 - Maddau, L. A1 - T. Jung A1 - Denman, S. ED - Andrea, V. AB -

Between 2008 and 2011, severe dieback associated with root and collar rot was reported on Arbutus unedo in several sites in Sardinia, Italy. Isolations from infected tissues and rhizosphere soil samples consistently yielded a Phytophthora species. It was initially identified as Phytophthora cinnamomi var. parvispora Kröber and Marwitz by comparing morphological features with the original description and the internal transcribed spacer (ITS) sequences with those present in GenBank. A multigene phylogeny based on DNA sequence data from two nuclear (ITS and β-tubulin) and two mitochondrial (cox1 and cox2) gene regions combined with extensive morphological and physiological properties of these isolates, including the ex-type culture of P. cinnamomi var. parvispora, demonstrates that this taxon is unique and it is redesignated here as Phytophthora parvispora sp. nov. Although morphologically similar to P. cinnamomi, P. parvispora differs by its smaller-sized sporangia, chlamydospores, oogonia and oospores, higher oospore wall index, single-celled antheridia, higher minimum and maximum temperatures for growth and faster growth at optimum temperature. In the phylogeny, P. parvispora falls within Phytophthora ITS clade 7a, grouped in a well-supported clade sister to P. cinnamomi. In pathogenicity tests, P. parvispora and P. cinnamomi were equally aggressive towards A. unedo seedlings. The possible geographic origin of P. parvispora is also discussed.

UR - http://onlinelibrary.wiley.com/doi/10.1111/efp.12064/abstract JO - For. Path. ER - TY - JOUR T1 - Occurrence of Phytophthora cinnamomi in cork oak forests in Italy JF - Forest Pathology Y1 - 2013 A1 - Scanu, B. A1 - Linaldeddu, B. T. A1 - Franceschini, A. A1 - Anselmi, N. A1 - A. Vannini A1 - A.M. Vettraino ED - Belbahri, L. AB -

An increasing decline and mortality of cork oak trees have been recently observed in central Italy and Sardinia Island. Following surveys conducted in three declining cork oak forests, a Phytophthora species was consistently isolated from soil samples collected from trees displaying different level of decline. Based on morphological features, growth rates at different temperatures and analysis of DNA sequences of the ITS region, all isolates were identified as Phytophthora cinnamomi Rands. This pathogen caused large brownish lesions on inoculated freshly cut branches of cork oak. It was re-isolated from all infected tissues. These findings represent the first report of P. cinnamomi on cork oak trees in Italy.

VL - 43 UR - http://onlinelibrary.wiley.com/doi/10.1111/efp.12039/abstract IS - 4 JO - For. Path. ER -