Molecular analysis ofPhytophthoradiversity in nursery‐grown ornamental and fruit plants

Abstract

The genetic diversity of Phytophthora spp. was investigated in potted ornamental and fruit tree species. A metabarcoding approach was used, based on a semi‐nested PCR with Phytophthora genus‐specific primers targeting the ITS1 region of the rDNA. More than 50 ITS1 sequence types representing at least 15 distinct Phytophthora taxa were detected. Nine had ITS sequences that grouped them in defined taxonomic groups (P. nicotianae, P. citrophthora, P. meadii, P. taxon Pgchlamydo, P. cinnamomi, P. parvispora, P. cambivora, P. niederhauserii and P. lateralis) whereas three phylotypes were associated to two or more taxa (P. citricola taxon E or III; P. pseudosyringae, P. ilicis or P. nemorosa; and P. cryptogea, P. erythroseptica, P. himalayensis or P. sp. ‘kelmania’) that can be challenging to resolve with ITS1 sequences alone. Three additional phylotypes were considered as representatives of novel Phytophthora taxa and defined as P. meadii‐like, P. cinnamomi‐like and P. niederhauserii‐like. Furthermore, the analyses highlighted a very complex assemblage of Phytophthora taxa in ornamental nurseries within a limited geographic area and provided some indications of structure amongst populations of P. nicotianae (the most prevalent taxon) and other taxa. Data revealed new host–pathogen combinations, evidence of new species previously unreported in Italy (P. lateralis) or Europe (P. meadii) and phylotypes representative of species that remain to be taxonomically defined. Furthermore, the results reinforced the primary role of plant nurseries in favouring the introduction, dissemination and evolution of Phytophthora species.

Diversity and detections of Phytophthora species from trade and non‐trade environments in Ireland

“…The total taxon richness of 21 (19 species and 3 informally named taxa) is greater than that of similar studies in Scotland (15 species; Schlenzig et al, 2015), Italy (15 species; Prigigallo et al, 2015) and Spain (17 species; Moralejo et al, 2009) although the present study did sample a wider range of habitats than any of the previous studies. The total taxon richness of 21 (19 species and 3 informally named taxa) is greater than that of similar studies in Scotland (15 species; Schlenzig et al, 2015), Italy (15 species; Prigigallo et al, 2015) and Spain (17 species; Moralejo et al, 2009) although the present study did sample a wider range of habitats than any of the previous studies.…”

Control of Phytophthora species in plant stock for habitat restoration through best management practices

“…The most likely way to prevent the introduction of Phytophthora species into wildlands through infected plant stock is with the implementation of ‘best management practices’ (BMPs) designed to prevent nursery‐grown plants from becoming infected in the first place (Baker, ). Consequently, there is an urgent need to identify proper management strategies that may successfully prevent the spread of the many diverse Phytophthora species found in nursery plant production (Hardy & Sivasithamparam, , ; Davison et al ., ; Prigigallo et al ., ). There are manuals describing BMPs designed to reduce the chances of establishment and spread of Phytophthora species in nurseries producing ornamental or other commercial crop plants (Griesbach et al ., ).…”

“…Studies have investigated the connectivity between the ornamental plant industry and the introduction of exotic Phytophthora species into wildlands in North America (Garbelotto & Hayden, 2012). In addition, a great number of previously unreported plant species 9 Phytophthora species combinations have been recently identified in nursery-grown ornamental and fruit crops (Prigigallo et al, 2015). However, no in-depth studies have been done regarding nurseries producing native plant stock for restoration, nor have any prevention programmes been used to try and stop the inadvertent spread of phytophthora disease through restoration efforts.…”

Age‐related susceptibility ofEucalyptusspecies toPhytophthora boodjera

“…Environmental conditions in nurseries such as warm temperature, over-watering, poor drainage and high seedling density are favourable to the development of disease epidemics caused by Phytophthora species (Old et al, 2003;P erez-Sierra & Jung, 2013;Jung et al, 2015;Prigigallo et al, 2015). Nursery propagation is a crucial stage of any Eucalyptus planting programme and vulnerability to losses of planting stock due to pre-and post-emergence damping off, or root and collar rot disease of older seedlings, can severely hamper their production (Gibson, 1975;Marks & Kassaby, 1976;Broembsen, 1984;Eldridge et al, 1994;Brown & Ferreira, 2000).…”