02904nas a2200181 4500008004100000245014300041210006900184260001600253300001400269520229100283100002102574700001702595700001902612700001402631700002102645700001302666856004302679 2016 eng d00aVisualizing the early infection of Agathis australis by Phytophthora agathidicida, using microscopy and fluorescent in situ hybridization0 aVisualizing the early infection of Agathis australis by Phytopht cJan-03-2016 an/a - n/a3 a

Phytophthora agathidicida (PTA) causes a root rot and collar rot of New Zealand kauri (Agathis australis). This study developed techniques to visualize early infection of kauri by PTA in deliberately inoculated seedlings. Conventional light microscopy was carried out on cleared and stained roots using trypan blue to observe PTA structures. Additionally, scanning electron microscopy (SEM) was used to study the PTA root structures at a higher resolution. A fluorescent in situ hybridization assay (FISH) was developed using a PTA-specific probe to label PTA structures in planta. Infection progression in roots of 2-year-old kauri inoculated with PTA at 5, 10, 16 and 20 days post-inoculation (d.p.i.) was compared using these three approaches. Light microscopy identified no Phytophthora-like structures in the control treatments. In PTA-inoculated plants, lignitubers were produced 5 d.p.i. in cortical cells. Infection was localized after 5 days, but as the infection progressed (up to 20 d.p.i.), the ‘degree’ of root infection increased, as did the number of replicates in which structures were observed. SEM provided higher resolution images; again, no PTA structures were observed in the negative control material examined. The slide-based FISH-specificity assay successfully hybridized with PTA hyphae. Fluorescence was observed using 330–380 nm excitation and an emission filter at 420 nm (DAPI), with PTA nuclei fluorescing a bright greenish-yellow. Cross-reactivity was not observed when the assay was applied to six other non-target Phytophthora species. Successful hybridization reactions occurred between the primer and PTA structures in planta. Applying this FISH assay has allowed clear differentiation of the intracellular and intercellular structures of PTA. The technique can be applied to longer term studies or analysis of ex situ inoculation studies aiming to elucidate differential host-responses to the pathogen. Additionally, the technique could be applied to study the interactions with other fungal endophytes (e.g. mycorrhizal fungi), which could be assessed for biocontrol potential as part of the integrated management of the disease.

1 aBellgard, S., E.1 aPadamsee, M.1 aProbst, C., M.1 aLebel, T.1 aWilliams, S., E.1 aJung, T. uhttp://doi.wiley.com/10.1111/efp.1228000572nas a2200121 4500008004100000020002200041245007200063210006900135260009800204300001000302100004900312856008900361 2008 eng d a978-1-74152-795-700aVictoria’s Public Land Phytophthora cinnamomi Management Strategy0 aVictoria s Public Land Phytophthora cinnamomi Management Strateg bDepartment of Sustainability and Environment, PO Box 500, East Melbourne, Victoria, Australia a37 pp1 aDepartment of Sustainability and Environment uhttp://lakeshub.com/wp-content/uploads/2013/04/Phytophthora_cinnamomi_Strategy-1.pdf02221nas a2200157 4500008004100000245010300041210006900144260001200213300001400225490000700239520172000246100001601966700001301982700001901995856004902014 2012 eng d00aVariation among Phytophthora cinnamomi isolates from oak forest soils in the eastern United States0 aVariation among Phytophthora cinnamomi isolates from oak forest  c11/2012 a1608-16140 v963 a

Phytophthora cinnamomi isolates from geographically diverse oak forest soils in the Mid-Atlantic regions were studied to determine the extent of genotypic, phenotypic, and pathogenic variation. Four microsatellite loci were targeted for genetic analysis. Phenotypic characteristics measured included sexual and asexual spore dimensions and colony growth rate and morphology. Red oak (Quercus rubra) logs were inoculated with selected isolates to determine relative pathogenicity. Microsatellite analysis showed that the genetic variability of P. cinnamomi isolates was low, with two predominant microsatellite fingerprint groups (MFG). Isolates in MFG1 (48% of the total isolates examined) were characterized by DNA fragment lengths of 120 and 122 bp at locus d39, 169 and 170 bp at locus e16, and 254 and 255 bp at locus g13. MFG2 isolates were characterized by marker sizes of 122 and 124 bp at locus d39, 161 and 163 bp at locus e16, and 247 and 248 bp at locus g13. Asexual and sexual spore dimensions varied greatly among isolates but were similar to previously published descriptions. Phenotypic differences were most pronounced when data were grouped by MFG; the most significant were colony morphology and growth rate. Neither characteristic was a reliable predictor of isolate genotype. Differences in growth rates of MFGs were observed, with MFG1 being less tolerant at higher incubation temperatures. No variation in pathogenicity was observed on red oak logs. The low level of phenotypic and genotypic variation of P. cinnamomi suggest that other factors such as climate might play a more important role in its northern distribution and the diseases it causes.

1 aEggers, J E1 aBalci, Y1 aMacDonald, W L uhttp://dx.doi.org/10.1094/PDIS-02-12-0140-RE02110nas a2200157 4500008004100000245013700041210006900178260001800247300001400265490000700279520156400286100002101850700002401871700001401895856004301909 2015 eng d00aVariation in pathogenicity among the three subspecies of Phytophthora alni on detached leaves, twigs and branches of Alnus glutinosa0 aVariation in pathogenicity among the three subspecies of Phytoph cDecember 2015 a484–4910 v453 a

Pathogenicity tests were carried out on leaves, twigs and branches of Alnus glutinosa using several isolates of Phytophthora alni ssp. alni, P. alni ssp. multiformis and P. alni ssp. uniformis in vitro. Healthy fresh leaves were collected from disease-free areas and inoculated with mycelium on agar discs or by dipping in zoospore suspensions. In addition, twigs and branches were collected from both disease-free and disease-affected areas, inoculated with mycelium on agar discs and incubated at four temperatures (15, 20, 25, 30°C). All subspecies tested were pathogenic but with varied level of virulence. In inoculation tests on foliage, wounding was a key factor in causing infections: lesions on inoculated wounded leaves were larger than on non-wounded leaves. In the twig and branch inoculation tests, no differences in virulence were observed among the P. alni subspecies in terms of sampling locations, but lesions differed in size according to incubation temperature, with the largest lesions occurring on tissues incubated at 25°C. The work is the first to report foliar necrosis caused by P. alni on A. glutinosa. P. alni ssp. uniformis was the least virulent of the subspecies in branch inoculations. These findings demonstrate that various tissues of A. glutinosa could act as sources of pathogen inoculum and may disseminate alder Phytophthora in natural ecosystems.

1 aHaque, M., M. U.1 aMartín-García, J.1 aDiez, J J uhttp://doi.wiley.com/10.1111/efp.1219801593nas a2200157 4500008004100000245013100041210007000172260001600242300001100258490000700269520094800276100002001224700001701244700001301261856016101274 2016 eng d00aVariation in Alnus glutinosa susceptibility to Phytophthora ×alni infection and its geographic pattern in the Czech Republic0 aVariation in Alnus glutinosa susceptibility to Phytophthora ×aln cJan-02-2016 a3 - 100 v463 a

Variation in natural susceptibility of the black alder population to Phytophthora ×alni (PA), the oomycete pathogen causing a devastating disease of alder, and its possible relationship to geographic origin, was studied in vitro using branch inoculation tests. Ninety black alder genotypes from different regions of the Czech Republic and two isolates of PA were employed. Host susceptibility varied significantly. After 1 week of infection, the lesion surface areas ranged from 254 to 2051 mm2 and from 19 to 970 mm2 for the two isolates, respectively. The differences were also dependent on the geographical origin and altitude of the sites from which particular host genotypes were taken. These findings have important implications for restoration plantings and for PA resistance breeding programmes, as there is potential to make selections from natural populations.

1 aŠtochlová, P.1 aNovotná, K.1 aCerny, K uhttp://doi.wiley.com/10.1111/efp.2016.46.issue-1http://doi.wiley.com/10.1111/efp.12205http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fefp.1220502140nas a2200169 4500008004100000022003100041245012500072210006900197260001600266300002000282520151300302100002601815700001901841700002001860700002401880856006601904 2019 eng d a0191-2917 e-ISSN:1943-769200aVariation in Susceptibility of Tanoak to the NA1 and EU1 Lineages of Phytophthora ramorum, the Cause of Sudden Oak Death0 aVariation in Susceptibility of Tanoak to the NA1 and EU1 Lineage cFeb-09-2021 aPDIS-04-19-08313 a

Phytophthora ramorum, the cause of sudden oak death (SOD), kills tanoak (Notholithocarpus densiflorus) trees in southwestern Oregon and California. Two lineages of P. ramorum are now found in wildland forests of Oregon (NA1 and EU1). In addition to the management of SOD in forest ecosystems, disease resistance could be used as a way to mitigate the impact of P. ramorum. The objectives of this study were to (i) characterize the variability in resistance of N. densiflorus among families using lesion length; (ii) determine whether lineage, isolate, family, or their interactions significantly affect variation in lesion length; and (iii) determine whether there are differences among isolates and among families in terms of lesion length. The parameters isolate nested within lineage (isolate[lineage]) and family × isolate(lineage) interaction explained the majority of the variation in lesion length. There was no significant difference between the NA1 and EU1 lineages in terms of mean lesion length; however, there were differences among the six isolates. Lesions on seedlings collected from surviving trees at infested sites were smaller, on average, than lesions of seedlings collected from trees at noninfested sites (P = 0.0064). The results indicate that there is potential to establish a breeding program for tanoak resistance to SOD and that several isolates of P. ramorum should be used in an artificial inoculation assay.

1 aSøndreli, Kelsey, L.1 aKanaskie, Alan1 aKeriö, Susanna1 aLeBoldus, Jared, M. uhttps://apsjournals.apsnet.org/doi/10.1094/PDIS-04-19-0831-RE