Liberibacter asiaticus (Asian greening).

Author(s):  
Esther Arengo

Abstract The Asian form of Huanglongbing is considered very invasive due to the cryptic nature of the disease and its ability to be transported either in infected plant material or infective psyllids, in which the disease can persist for up to 3 months (da Graca and Korsten, 2004). Yield losses due to this disease have been estimated to be between 30% and 100%, depending on the proportion of the canopy affected and the age of the trees during inoculation (Gottwald, 2010; Ammar et al., 2011). History has shown that the appearance of the vector in a country will almost guarantee the appearance of the disease in the future, e.g. in Brazil and Florida, USA. The species and its vector are on several alert lists including the EPPO A1 Regulated Quarantine Plant Pests.

2017 ◽  
Vol 38 (SI 2 - 6th Conf EFPP 2002) ◽  
pp. 249-251
Author(s):  
P. Ryšánek ◽  
M. Zouhar ◽  
M. Hassan

Peach latent mosaic viroid (PLMVd) is widespread in peach all over the world. It has never been reported from the Czech Republic. That is why we adapted specific and sensitive method for its detection, PCR, to be able to prove its possible occurrence and for certification purposes. Primers PLMVdR, PLMVdF1 and PLMVdF2 were designed on the basis of published RNA sequences. Products of amplification are 208 and 114 bp long for PLMVdF1 and PLMVdF2, respectively. Four PLMVd isolates from Dr Di Serio (CNR Bari) were used as standards. Potato spindle tuber viroid and Hop latent viroid infected plant material and also healthy material were used to check detection specifity. Both RNA extraction from plant material and PCR were optimalized so that this method of PLMVd detection can also be used for certification purposes.


2011 ◽  
Vol 61 (3) ◽  
pp. 489-497 ◽  
Author(s):  
J. Adriko ◽  
V. Aritua ◽  
C. N. Mortensen ◽  
W. K. Tushemereirwe ◽  
J. Kubiriba ◽  
...  

2006 ◽  
Vol 96 (8) ◽  
pp. 900-907 ◽  
Author(s):  
Pablo Llop ◽  
Victoria Donat ◽  
Margarita Rodríguez ◽  
Jordi Cabrefiga ◽  
Lídia Ruz ◽  
...  

An atypical strain of Erwinia amylovora was isolated near an outbreak of fire blight at a nursery in Spain in 1996. It was obtained from a Crataegus plant showing typical symptoms and was identified as E. amy-lovora by biochemical tests and enrichment-enzyme-linked immuno-sorbent assay, but not by polymerase chain reaction using primers based on the pEA29 sequence. Nevertheless, with primers from chromosomal regions, the isolate gave the expected amplification band. This strain carries one plasmid of ≈70 kb, with no homology with the 29-kb plasmid common to all pathogenic strains, or with a large plasmid present in some E. amylovora strains. Growth of the strain in minimal medium without thiamine was slower compared with cultures in the same medium with thiamine, a characteristic typical of strains cured of the 29-kb plasmid. Nevertheless, aggressiveness assays on pear, apple, and Pyracantha plants and in immature pear fruit showed that this strain exhibited a virulence level similar to other strains containing pEA29. To the best of our knowledge, this is the first report of the isolation from naturally infected plant material of a pathogenic strain of E. amylovora without pEA29, but with a plasmid of ≈70 kb not previously described.


2013 ◽  
Vol 16 (4) ◽  
pp. 765-774 ◽  
Author(s):  
Andrew Yufa Li ◽  
Nari Williams ◽  
Stanley G. Fenwick ◽  
Giles E. St. J. Hardy ◽  
Peter J. Adams

2016 ◽  
Vol 334 ◽  
pp. 27-43 ◽  
Author(s):  
Andrew M. Bate ◽  
Glyn Jones ◽  
Adam Kleczkowski ◽  
Alan MacLeod ◽  
Rebecca Naylor ◽  
...  

Author(s):  
Adonise F. Valam Zango ◽  
Innocent Zinga ◽  
Régis Dimitri Longué Soupké ◽  
Simplice Prosper Yandia ◽  
Brice Toko Marabana ◽  
...  

Aim: The production of healthy cuttings from a local cassava cultivar for cassava mosaic control. Study design: The study was carried out at the In Vitro Culture Laboratory using the techniques of thermotherapy and culture of tissues and explants in a specific medium. Place and duration: The study was carried out at the Laboratory of Biological and Agronomic Sciences for Development at the University of Bangui, Central African Republic from December 2017 to June 2018. Methodology: A variety of cassava called six-month very susceptible to mosaic was used for this work. The cuttings used were infected by Cassava Mosaic Begomoviruses (CMBs) with high severity. It were subcultured in a room under the heat of 37 ° C to 40 ° C for two weeks. Explants and meristems were taken from the stems and the apices, respectively. These collected materials were treated and seeded on appropriate culture media. After the plants produced in vitro were acclimatized and the leaves were removed to check their phytosanitary state by the PCR technique. Results: The rate of emergence of the acclimatized plants and the expression of the disease on the microplants were evaluated. The results show that 75% of the weaned vitro plants recovered under acclimatization. In addition, the acclimatized plants left growing in the greenhouse for four months remained asymptomatic. Molecular analysis by PCR showed that begomoviruses were not detected on meristem samples unlike samples from stem fragments. Conclusion: The combination of thermotherapy technique associated with the culture of meristems constitutes an effective means useful for the sanitation of infected plant material.


2019 ◽  
Author(s):  
Luigi Faino ◽  
Valeria Scala ◽  
Alessio Albanese ◽  
Vanessa Modesti ◽  
Alessandro Grottoli ◽  
...  

SummaryXylella fastidiosa (Xf) is a polyphagous gram-negative bacterial plant pathogen that can infect more than 300 plant species. It is endemic in America while, in 2013, Xf subsp. pauca was for the first time reported in Europe on olive tree in the Southern Italy. The availability of fast and reliable diagnostic tools is indispensable for managing current and future outbreaks of Xf.In this work, we used the Oxford Nanopore Technologies (ONT) device MinION platform for detecting and identifying Xf at species, subspecies and Sequence Type (ST) level straight from infected plant material. The study showed the possibility to detect Xf by direct DNA sequencing and identify the subspecies in highly infected samples. In order to improve sensitivity, Nanopore amplicon sequencing was assessed. Using primers within the set of the seven MLST officially adopted for identifying Xf at type strain level, we developed a workflow consisting in a multiple PCR and an ad hoc pipeline to generate MLST consensus after Nanopore-sequencing of the amplicons. The here-developed combined approach achieved a sensitivity higher than real-time PCR allowing within few hours, the detection and identification of Xf at ST level in infected plant material, also at low level of contamination.Originality Significance StatementIn this work we developed a methodology that allows the detection and identification of Xylella fastidiosa in plant using the Nanopore technology portable device MinION. The approach that we develop resulted more sensitive than methods currently used for detecting X. fastidiosa, like real-time PCR. This approach can be extensively used for X. fastidiosa detection and it may pave the road for the detection of other tedious vascular pathogens.


Author(s):  
D. Brayford

Abstract A description is provided for Cylindrocarpon musae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Musa AAA (Cavendish). DISEASE: Rotting of fleshy roots and rhizomes of banana. GEOGRAPHICAL DISTRIBUTION: Asia: Philippines; North America: Costa Rica, Guadeloupe, Martinique, Panama; South America: Colombia, Ecuador. TRANSMISSION: The fungus probably survives as 'chlamydospores' in soil. Its slimy spores may be dispersed by water. Long distance spread may potentially occur by transportation of infected plant material or contaminated soil.


2016 ◽  
Vol 106 (9) ◽  
pp. 1006-1014 ◽  
Author(s):  
Antonio Biasi ◽  
Frank N. Martin ◽  
Santa O. Cacciola ◽  
Gaetano Magnano di San Lio ◽  
Niklaus J. Grünwald ◽  
...  

In all, 231 isolates of Phytophthora nicotianae representing 14 populations from different host genera, including agricultural crops (Citrus, Nicotiana, and Lycopersicon), potted ornamental species in nurseries (Lavandula, Convolvulus, Myrtus, Correa, and Ruta), and other plant genera were characterized using simple-sequence repeat markers. In total, 99 multilocus genotypes (MLG) were identified, revealing a strong association between genetic grouping and host of recovery, with most MLG being associated with a single host genus. Significant differences in the structure of populations were revealed but clonality prevailed in all populations. Isolates from Citrus were found to be genetically related regardless of their geographic origin and were characterized by high genetic uniformity and high inbreeding coefficients. Higher variability was observed for other populations and a significant geographical structuring was determined for isolates from Nicotiana. Detected differences were related to the propagation and cultivation systems of different crops. Isolates obtained from Citrus spp. are more likely to be distributed worldwide with infected plant material whereas Nicotiana and Lycopersicon spp. are propagated by seed, which would not contribute to the spread of the pathogen and result in a greater chance for geographic isolation of lineages. With regard to ornamental species in nurseries, the high genetic variation is likely the result of the admixture of diverse pathogen genotypes through the trade of infected plant material from various geographic origins, the presence of several hosts in the same nursery, and genetic recombination through sexual reproduction of this heterothallic species.


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