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Xylella fastidiosa is a xylem‐limited bacterial plant pathogen transmitted by insect vectors. It infects a wide range of plant species and causes devastating diseases. Botanical gardens are global repositories of plant diversity exposed to local biotic and abiotic stresses. We used molecular diagnostic tools for the detection of X. fastidiosa in a collection of New Zealand indigenous plants grown in a X. fastidiosa‐infected Californian area to determine if any species were infected with this bacterial pathogen and to help inform biosecurity responses. To this end, 130 New Zealand indigenous plant species comprising 72 genera, growing in the University of California Botanical Garden at Berkeley, California, were screened for X. fastidiosa. Multiple PCR‐based methods were used to detect the pathogen at the subspecies and sequence‐type levels directly from plant material; nine plant species tested positive by at least two PCR‐based methods. All nine infections were identified as X. fastidiosa subsp. multiplex sequence types 6 or 7 by the amplification of seven housekeeping genes. Three strains were cultured in vitro and their whole genome sequences were obtained; these strains belonged to three distinct clades within subspecies multiplex, indicating that the infections were not transmitted among these New Zealand indigenous plant species. The information gathered in this study will help to assess the risk of X. fastidiosa to New Zealand indigenous flora and the potential spillover to crops of agricultural importance. The work also shows the applied value of botanical garden collections as sentinels for international plant pathogen biosecurity risk assessment. [ABSTRACT FROM AUTHOR]

Previously genetically characterised strains of Pseudomonas syringae. pv. syringae (Pss), [P. amygdali pv. morsprunorum] (Pam, syn. P. s. pv. morsprunorum race 1) and Pseudomonas spp. from New Zealand were characterised for their pathogenicity and aggressiveness in plant tissue and associated virulence factors. Lesions on detached, Pss‐inoculated immature fruit increased rapidly in size and, at 10 days post inoculation (dpi), had larger areas under the disease progress curve (AUDPC) than Pam‐inoculated fruit (48.9 and 22.0, respectively). Detached leaves infiltrated with Pss‐developed symptoms within 1 dpi and from 2 dpi for Pam. Necrosis from most Pss strains extended into the leaf veins by 7 dpi, while Pam strains' necrosis was confined to the inoculation site. On detached 1‐year‐old cherry shoots, Pseudomonas spp. strains exhibited the smallest mean lesion size (2.1–2.4 mm), whereas larger mean lesion sizes were observed with Pss strains (5.7–13.7 mm) and Pam strains (3.9–14.0 mm). A functional T3SS was inferred for Pss and Pam strains based on the hypersensitivity reactions observed on tobacco leaves and symptoms elicited on cherry tissue. Syringomycin production was prevalent (88%) among Pss strains. In contrast, only 1.4% of Pam strains produced coronatine. Most Pss strains (97.0%) were able to catalyse ice formation. The coexistence of strains with varying degrees of virulence and non‐pathogenic strains suggests a complex ecological balance, where multiple factors, including genetic variation, virulence traits and environmental conditions, shape the population dynamics and disease outcomes. [ABSTRACT FROM AUTHOR]

Bacterial canker of cherry, caused by Pseudomonas syringae pathovars, is a major constraint to cherry growing in New Zealand. The prevalence of strains from cherry orchards in Central Otago, the main growing area for cherries in New Zealand, was studied, to better understand the epidemiology of the disease. Pseudomonas spp. isolates were collected from symptomatic and asymptomatic cherry tissue from 23 commercial cherry orchards in 2015. Isolates were classified into strains belonging to three different taxonomic groups by determining their phylogeny using the gltA gene sequence for all the strains and multilocus sequence analysis (MLSA) of four housekeeping genes for 35 strains. Pathogenicity of all Central Otago strains was tested on immature cherry fruit to support the phylogenetic classification. The two main taxonomic groups were P. syringae pv. syringae (Pss) and P. syringae pv. morsprunorum race 1 (Psm1), in Phylogroup 2 (PG2) and Phylogroup 3 (PG3), respectively. The third group comprised nonpathogenic strains classified as Pseudomonas spp. Strains of Psm1 formed a monophyletic group, representing an almost clonal population. There was more variation detected within strains of Pss, although they were restricted to group PG2d. Nonpathogenic Pseudomonas spp. and pathogenic Pss and Psm1 strains coexisted in the same orchard. It was concluded that Pss is the predominant pathovar in Central Otago. This is the first detailed study of the P. syringae species complex in cherry orchards in New Zealand and provides the basis for future epidemiology studies. [ABSTRACT FROM AUTHOR]

The ITS1-5.8S-ITS2 rRNA (internal transcribed spacer (ITS)) region is used for examining the phylogenetic relationships of Rhizopogon roseolus and other closely related fungi belonging to Rhizopogon subgenus Roseoli in order to determine the genetic basis for phenotypic differences among R. roseolus isolates from different geographic regions. The ITS region is used for designing a multiplex PCR for the simultaneous identification of Japanese and New Zealand R. roseolus isolates in order to track the establishment of ectomycorrhiza on Pinaceae radiate seedlings inoculated with commercially valuable R. roseolus.

We present an account of Rhizopogon introduced from plantings of exotic pine plantations in Argentine Patagonia. Nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS) and nuc 28S rDNA (28S) sequences were used to identify specimens from Argentina and examine their relationships with geographically different Rhizopogon species. Based on phylogenetic analyses, we confirm that four species of Rhizopogon occur in pine plantations across Patagonia. Several Rhizopogon collections from Pinus ponderosa plantations across different provinces cluster with R. arctostaphyli, a species within R. subg. Amylopogon. The majority of Patagonian Rhizopogon, however, form three different lineages in R. subg. Roseoli. The first of these, R. roseolus sensu Trappe, includes numerous collections from Pinus ponderosa, P. contorta, and P. radiata stands of North American affiliation. The second, R. roseolus sensu Martin and Garcia from P. ponderosa plantations, clusters in clade IIIa of the R. roseolus complex, which also includes the holotype collection of R. mohelnensis from the Czech Republic. The third species in R. subg. Roseoli, and fourth species overall from Patagonia, is R. granuloflavus from Pinus ponderosa plantations. Multiplex polymerase chain reaction (PCR) of numerous Roseoli samples failed to produce an amplicon indicative of either Japanese or New Zealand shoro. [ABSTRACT FROM AUTHOR]