Characterization of Pseudomonas syringae pv. actinidiae biovar 3 on kiwifruit in north-west Portugal.

AIMS: Bacterial kiwifruit canker disease, caused by Pseudomonas syringae pv. actinidiae (Psa) was detected in north-west Portugal in 2010, and has since caused significant losses. The objectives of this work were to characterize the Portuguese population(s) of Psa and to define the actual prevalence of Psa biovars in the most productive kiwifruit region in Portugal. METHODS AND RESULTS: Isolates obtained from Actinidia deliciosa orchards were characterized by morphological, biochemical, physiological, fatty acids and molecular tests (PCR, BOX-PCR, duplex-PCR, multiplex-PCR and RFLP), phaseolotoxin, housekeeping and effector genes and pathogenicity. Results established that only Psa biovar 3 is present in the north-west of Portugal, despite phenotypic and genetic variability among the isolates. CONCLUSIONS: This work provides new information on P. syringae pv. actinidiae (Psa) genetic profile in Portugal, indicating for the first time, that two genetically different subpopulations of Psa biovar 3 are present. SIGNIFICANCE AND IMPACT OF THE STUDY: A new subpopulation of Psa biovar 3 was found for the first time in Portugal, contributing to increase knowledge about this population worldwide and to support further understanding of the impact of Psa.

Detection and characterization of Pseudomonas syringae pv. actinidifoliorum in kiwifruit in Spain.

AIMS: Bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae (Psa) is currently the major threat to its commercial production worldwide. In 2011, the most virulent type (Psa3) was detected for the first time in Northwest-Spain, in the province of Pontevedra. In 2013 surveys, leaves and flower buds with mild symptoms were observed in Actinidia deliciosa 'Hayward' vines in an orchard at the province of A Coruña, suggesting the presence of P. syringae pv. actinidifoliorum (Psaf). METHODS AND RESULTS: Isolates obtained from such orchard were characterized by morphological, biochemical and physiological tests, fatty acids (FA) profile and molecular tests (PCR, BOX-PCR, duplex PCR, multiplex PCR, real-time PCR, PCR-C, phytotoxins, housekeeping and effector genes). Pathogenicity tests were also carried out on plants and fruits of A. deliciosa 'Hayward' and on different cultivated plants and fruits. Results demonstrated the presence of P. syringae pv. actinidifoliorum in Spain. CONCLUSIONS: The work provides new information on the pathovar P. syringae pv. actinidifoliorum, which has only been found previously in New Zealand, Australia and France. SIGNIFICANCE AND IMPACT OF STUDY: The results are relevant for taxonomy of isolates of P. syringae from kiwifruit, especially those of low virulence not belonging to pathovar actinidiae.

Detection of Bursaphelenchus Xylophilus, Causal Agent of Pine Wilt Disease on Pinus pinaster in Northwestern Spain.

The pine wood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, a quarantine organism, causes serious damage to pines worldwide. In Europe, it was first detected in Portugal in 1999 (3) and the pathogen was thought to be restricted to this area. However, in 2008, B. xylophilus was isolated from a single tree in the Cáceres Region (Extremadura) of Spain, bordering Portugal (2). The region of Galicia has approximately 383,632 ha of Pinus pinaster Aiton that constitutes more than 40% of the surface of Spain. Since 1999, we have analyzed 5,155 samples to monitor the presence of the pathogen. In 2008, a Spanish national contingency plan established three delimiting sampling areas, including a high risk area 20 km from the border with Portugal (2 × 2 km grid), a medium risk area 80 km wide (4 × 4), and another area covering the whole region (8 × 8). The plan required collecting samples from symptomatic trees. In 2010, in the high risk area, 307 sites were surveyed in coniferous forests. At each site, wood chip samples were collected from five pine trees. The collected wood chips were then incubated for 15 days in the lab and nematodes were extracted by Baermann's funnel method. B. xylophilus was detected from a decayed mass of P. pinaster from the As Neves Municipality (Pontevedra, Galicia). Affected specimens showed typical symptoms associated with pine wilt, including needle discoloration and death of branches. B. xylophilus was identified by morphological and molecular methods. Morphological characteristics included high lips, constricted heads, and short stylets with reduced basal knobs. Females had rounded tails, some with a short mucro, and flat vulva, while males had spicules curved with a cucullus. Measurements of these nematodes (10 females: body length = 720.99 ± 123.87 µm, a = 41.07 ± 5.83, b = 9.22 ± 3.44, c = 26.57 ± 4.13, V = 73.2, stylet length = 14.91 ± 1.65 µm; 10 males: body length = 576.4 ± 88.16 µm, a = 38.12 ± 5.36, b = 7.83 ± 0.39, c = 23.07 ± 2.59, stylet length = 14.63 ± 1.95 µm, spicules length = 22.5 ± 2.21 µm) were similar to the isolates found in Portugal described by Penas et al.(4) and smaller than described by Mota et al. (3). Molecular diagnosis was done following the protocols recommended by the EPPO (1): (i) Amplification of satellite DNA of B. xylophilus by PCR obtaining fragments of 160, 320, and 480 bp; (ii) PCR amplification of a region of 77 bp satellite DNA of B. xylophilus by Taqman Real Time; and (iii) PCR-restriction fragment length polymorphism of the internal transcribed spacer (ITS) region of Bursaphelenchus spp. nrDNA obtaining the restriction pattern for B. xylophilus. The ITS product amplified by PCR was also sequenced, showing a 99% homology with the sequences of B. xylophilus deposited in GenBank. A sequence of this nematode was submitted to GenBank database and assigned the number HQ646254. On the basis of these diagnostic characteristics, we have confirmed that B. xylophilus is now present in Galicia (northwestern Spain), which is one of the most productive and important region of Spain for forestry. References: (1) EPPO Bull. 39:344, 2009. (2) EPPO Rep. Serv. 3:2010/051, 2010. (3) M. M. Mota et al. Nematology 1:727, 1999. (4) A. C. Penas et al. J. Nematol. Morphol. Syst. 10:137, 2008.

First Report of Bacterial Canker of Kiwifruit Caused by Pseudomonas syringae pv. actinidiae in Spain.

Bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae was first described in Japan and Korea and is currently an emerging disease that causes major losses in China, Italy, New Zealand, France, Portugal, and Chile. Gold kiwifruit (Actinidia chinensis), especially cvs. Jin Tao and Hort 16A, seem to be more susceptible than green kiwifruit (Actinidia deliciosa) cvs. Hayward and Summer. The bacterium affects male and female woody vines equally, with young vines being more susceptible. The most characteristic symptoms that appear in early spring are reddish orange or white exudates associated with cankers and wounds in branches and/or trunk, as well as brown leaf spots. Buds and fruits were also affected (1). In Spain, 1,132 ha of kiwifruit orchards yielded 25,285 t of fruit in 2009 (2). Most Spanish kiwifruit is cultivated in Galicia (northwest Spain), where the main cultivar is Hayward. In 2010, the first plantation of cv. Jin Tao and one plantation of cv. Summer were established in this area close to Hayward woody vine. In early spring 2011, 80% of the vines in one orchard had twigs with reddish exudates and branches and trunks as well as leaves with angular spots surrounded by yellow haloes. Isolations from both Actinidia spp. were conducted on nutrient agar with sucrose. One hundred and twelve isolates were obtained and seventy-seven were aerobic, gram negative and nonfluorescent on King's B medium. Biochemical tests performed were levan, oxidase, potato rot, arginine didhydrolase, hypersensitivity in tobacco, and utilization of 49 carbohydrates by the API 50 CH system (BioMérieux, Marcy l'Etoile, France). Three PCR protocols were used: two with pathovar-specific primers (PSAF1/PSAR2 and PSAF3/PSAR4) and one with nonspecific primers (PsITSF1/PsITSR2) (3). The results of all biochemical and molecular tests were in agreement with those expected for P. syringae pv. actinidiae. The 16S-23S region of strain EFA 37 isolated from A. deliciosa cv. Summer was sequenced (GenBank Accession No. JF815537) and had 100% sequence identity with P. syringae pv. actinidiae (GenBank Accession Nos. AY342165 and D86357). Pathogenicity tests were performed on 15 plants of A. deliciosa cv. Hayward (five plants per isolate) with the Spanish representative strain EFA 37 and compared with two reference strains isolated from both Actinidia species in Italy and five plants of an untreated control. Three buds per healthy vine were wounded with a sterile needle, inoculated with 30 to 50 µl of each bacterial suspension (108 CFU/ml), sealed, and then covered with plastic. Five leaves per healthy vine were also pierced with a sterile needle and then atomized with the same suspension. Symptoms began to appear after 5 days on inoculated vines, but not on untreated control vines. The bacterium, P. syringae pv. actinidiae, was reisolated from symptomatic plants. The kiwifruit orchard with affected plants was eradicated (25 ha). To our knowledge, this is the first report of P. syringae pv. actinidiae in Spain. References: (1) EPPO Alert List. Online publication. Retrieved from http://www.eppo.org/QUARATINE/Alert_List , June, 2011. (2) Ministerio de Medio Ambiente y Medio Rural y Marino (MARM). Anuario de Estadística, Online Publication. Retrieved from http://www.marm.es/estadistica/pags/anuario/2010 , June 2011. (3) J. Rees-George et al. Plant Pathol. 59:453, 2010.

First Report of a Root Rot Caused by Rosellinia necatrix on Camellia in Spain.

Camellias are widely cultivated in gardens and grown in nurseries for plant and flower production in northwestern Spain. Camellia japonica L. is most frequently grown, but many other camellia species and hybrids are also produced. In spring 1998, plants of Camellia sp. from a garden were observed to be affected by a root fungal pathogen, that formed a white mycelium that covered most of the roots, while aboveground plant parts showed a general decline. Infected roots were macerated and discolored. Fragments of the infected roots were surface-sterilized and placed in petri dishes containing potato dextrose agar and incubated at 24°C in the dark. The fungus formed a white mycelium that turned black in 1 week, developing pyriform swellings characteristic of Rosellinia necatrix Prill (1). To confirm pathogenicity, inoculum of the isolate was produced on wheat (Triticum aestivum L.) seeds autoclaved in glass vessels for 30 min at 120°C. Wheat seed cultures were started from disks of R. necatrix mycelium and grown at 24°C in the dark for 30 days. Pathogenicity tests were conducted on 48 2-year-old plants of the hybrid Camellia × williamsii cv. Mary Phoebe Taylor, which had been grown in 1.5-liter pots (one plant per pot) filled with soil in a glasshouse. The R. necatrix isolate was inoculated by adding 30 g of infected wheat seeds to each pot. The inoculum was mixed thoroughly with the substrate before potting. Another set of pots was left uninoculated, and served as a control. All pots were randomly arranged in a growth chamber at 22 to 24°C with a 12-h photoperiod. Seventeen days after inoculation, aerial symptoms of chlorosis and leaf fall were observed, while control plants remained symptomless. Inoculated plants died 3 months after inoculation. R. necatrix was reisolated from roots of all infected plants. To our knowledge, this is the first report of a root rot of camellia caused by R. necatrix, a pathogen causing white root rot mainly in deciduous fruit crops. Reference: (1) S. Freeman and A. Sztejnberg. Pages 71-73 in: Methods for Research on Soilborne Phytopathogenic Fungi. The American Phytopathological Society, St. Paul, MN, 1992.