1,342 research outputs found
Malattia di Castleman multicentrica associata a sarcoma di Kaposi Savoia P, Fierro MT, Quaglino P, Zaccagna A, Bernengo MG
No full textMolecular genotyping of Candidatus Phytoplasma solani strains identified in different crops in Jordan
No full textRecent surveys on phytoplasma-associated diseases in Jordan highlighted that ‘Candidatus Phytoplasma solani’ (CaPsol) is the prevalent phytoplasma throughout the Country. It was largely reported in several crops exhibiting different symptoms, in wild plants (CaPsol plant hosts), and putative insect vectors (Abu Alloush et al., 2023a,b, 2024). To improve the knowledge of CaPsol ecology, this study investigated the genetic diversity within CaPsol strain population identified in multiple crops in Jordan.
MATERIALS AND METHODS
DNA extracts from 51 CaPsol-infected plants of 8 crops, selected from previous studies (Abu Alloush et al., 2023a,b, 2024) (Table 1), were used as templates in direct and nested PCRs for the amplification of tufB, stamp, and vmp1 genes, carried out as previously described (Aryan et al., 2014; Fabre et al., 2011). To genotype CaPsol strains identified in Jordan, nucleotide sequences of obtained PCR products were compared with those of representative CaPsol strains previously described (Pierro et al., 2018; Jamshidi et al., 2022).
RESULTS AND DISCUSSION
Expected amplicons of tufB, stamp, and vmp1 genes were obtained from all the 51 CaPsol-infected plants analyzed. Surprisingly, considering the high genetic diversity generally present within CaPsol strain populations in a specific geographic area (Quaglino et al., 2021; Jamshidi et al., 2022), nucleotide sequence analyses revealed that all 51 CaPsol strains share identical tufB, stamp, and vmp1 gene sequences, highlighting there is no genetic variability in CaPsol strain populations in Jordan. Comparison with previously described CaPsol genotypes revealed that Jordanian CaPsol strains share sequences identical to genotypes tuf b-1 (strain CrHo12_601, Acc. No. KJ469708), St15 (strain P7, Acc. No. FN813258), and Vm53 (strain P7, Acc. No. AM992100), previously identified in Lebanon and Georgia (Caucasus region) and associated with bindweed-related pathosystem (Quaglino et al., 2016; Pierro et al., 2018). Further studies will investigate the diffusion of CaPsol genotype tuf b-1/St15/Vm53 in additional plant hosts and putative insect vectors to study the epidemiological patterns of CaPsol-associated diseases in Jordan
Sequencing of the ribosomal protein gene rpl16 from Candidatus Phytoplasma ulmi infecting a historic Ulmus minor
No full textThe aim of this work is to obtain new sequences of ‘Candidatus Phytoplasma ulmi’ useful for the characterization of phytoplasmas
infecting a historic plant of Ulmus minor. At our knowledge, we described for the first time the rpl16 gene sequence of ‘Ca.
P. ulmi’ strain ULW (elm witches’ broom). This gene, positioned downstream the gene rps3, codifies the ribosomal protein L16
First report of 'Candidatus Phytoplasma solani' associated with grapevine "bois noir" disease in Jordan
No full textBackground and objectives
Bois noir (BN) is a disease of the grapevine yellows (GY) complex associated with phytoplasmas of the species 'Candidatus Phytoplasma solani', taxonomic subgroup 16SrXII-A, mainly transmitted by the polyphagous Cixiidae Hyalesthes obsoletus Signoret (Alma et al., 1987; Quaglino et al., 2009, 2013). BN is largely spread in Europe and in Countries of the Mediterranean Basin, but in the last years its presence was reported also in South America, in South Africa, and in China (Botti and Bertaccini, 2006; Gajardo et al., 2009; Duduk et al., 2010). In the present work, we communicate the first report of BN in Jordan.
Materials and Methods
A survey was carried out in Jordan vineyards in August and October 2012, grapevine plants showing typical grapevine yellows (GY) disease symptoms were observed. In the same vineyards, bindweed plants showing stunting and leaf chromatic alteration were found suggesting the involvement of phytoplasmas in the disease etiology. Total DNA was extracted from leaf veins of 25 symptomatic and two asymptomatic grapevines, and from five symptomatic and two asymptomatic bindweeds. Phytoplasma detection by nested PCRs carried out using universal primer pairs P1/P7 followed by R16F2n/R16R2 (F2n/R2) (Lee et al., 1998). DNAs from periwinkle plants infected by ‘Ca. P. asteris’ strain SAY (group 16SrI), ‘Ca. P. solani’ strain STOL (group 16SrXII), and 'Ca. P. ulmi’ strain EY1 (group 16SrV), were used as positive controls. DNAs from healthy periwinkle and reactions without template DNA were employed as negative controls. F2n/R2 PCR products amplified from grapevines and bindweeds were sequenced and analysed through the software BlastN (sequence identity), BioEdit (alignment), iPhyClassifier (group/subgroup affiliation), and MEGA 5 (phylogeny).
Results and Discussion
Amplification of a band of the expected size (1250 nt) in three grapevines and in five bindweeds, and in the positive controls through 16S rDNA nested PCRs was observed. No amplification with DNA from 22 symptomatic grapevines, probably because samples were collected late in the growing season and phytoplasma distribution in plants was non-uniform (Constable et al., 2003), nor from asymptomatic plants and negative controls. Amplicons were not produced with DNA from 22 symptomatic grapevines (probably because samples were collected late in the growing season and phytoplasma distribution in plants was non-uniform (Constable et al., 2003), nor from asymptomatic plants and negative controls. PCR products were sequenced by commercial services in Italy (Primm, Milan) and Korea (Macrogen Inc., Soul). Representative 16S rDNA nucleotide sequences were deposited in NCBI GenBank with accession 30 nos. KC835139 (from grapevine) and KC835140 (from bindweed). The 16S rDNA nucleotide sequences of phytoplasmas identified in grapevine and bindweed in Jordan shared >99.5% sequence identity with 'Ca. Phytoplasma solani' reference strain STOL (AF248959), and carried identical STOL-unique signature sequences and distinguishing sequence blocks (Quaglino et al., 2013). Phylogenetic and in silico RFLP (Figure 2) analyses confirmed the affiliation of phytoplasma strains identified in grapevine and bindweed in Jordan to the species 'Ca. Phytoplasma solani' (subgroup 16SrXII-A), opening an avenue to future studies on the dissemination and impact of Bois noir (BN) in Jordan. These studies may add new information about BN, previously reported in neighboring countries (Davis, et al., 1997; Choueiri et al., 2002). Further studies will investigate the role of Hyalesthes obsoletus Signoret, a polyphagous Cixiidae responsible for the BN phytoplasma transmission in Europe, and other possible insect vector(s) in the BN spread in Jordan
Isolation of potential biocontrol agents of 'Candidatus Phytoplasma mali'
No full textBackground and objectives
Apple proliferation (AP), caused by ‘Candidatus Phytoplasma mali’, is one of the most important phytoplasma diseases in Europe. So far, due to the absence of AP resistant varieties, the management of AP mainly consists in insecticide treatment against the insect vectors and in the eradication of diseased plants. These treatments have a strong economic and environmental effect, representing a risk for both operators and final customers. One of the most innovative solutions to develop sustainable approaches is the use of endophytes as inducers of the natural plant defense responses. Bacterial endophytes are plant-associated bacteria that affect the plant life cycles in different manners such as nitrogen fixation or the biocontrol of plant pathogens (Lugtemberg and Kamilova 2009). A basic point for the success of sustainable management of plant diseases based on biocontrol agents is the study of endophytic bacterial community associated with plants. In this work, the endophytic bacterial community associated with healthy and AP phytoplasma-infected apple roots was described and characterized in order to find potential biocontrol agents.
Materials and Methods
Apple roots were collected from five asymptomatic and five AP-symptomatic plants during field survey conducted in 2010 in North-western Italy. Roots were opportunely sterilized and the total DNA was extracted with the method describe by Doyle and Doyle (1990), with some modifications. Extracted DNA was used as template for ‘Ca. Phytoplasma mali’ identification by (PCR)-based amplification of ribosomal RNA genes. In detail, ‘Ca. Phytoplasma mali’ was detected by the use of primer pairs fAT/rAS specific for 16SrX phytoplasmal group (Smart et al., 1996). Endophytic bacterial community associated with healthy and ‘Ca. Phytoplasma mali’-infected apple roots was described by cultivation dependent and independent methods (16S rRNA gene library analyses and sequencing). Endophytic bacteria were isolated by cultivation on Tryptic Soy Agar (TSA) and Luria-Bertani (LB). Total DNA from bacterial colonies was extracted and the 16S rRNA genes were amplified with bacterial universal primers and sequenced. The endophytic bacteria isolated on culture media were characterized for five beneficial traits related to mineral nutrition (phosphate solubilization, siderophores, nitrogen fixation), development (indolacetic acid synthesis), stress relief (catalase activity), disease control (siderophores).
Results and Discussion
The diversity of microbiota associated with healthy and phytoplasma-infected apple roots was investigated both with cultivation-independent and -dependent methods in order to increase the range of diversity explored in a sample. In this study, 16S rRNA gene libraries from infected and uninfected apple roots were analyzed to describe the endophytic bacterial community. A total of 120 clones were sequenced, 76 clones from the healthy roots and 44 from the infected ones. 16S rDNA sequence analysis showed the presence of the groups Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chlamydiae, and Firmicutes. In detail, library analyses underscored 24 and 17 Operational Taxonomic Units (OTUs) in healthy and infected roots, respectively, with a dominance of Betaproteobacteria. Also in previous work, clone library analysis of plant-associated bacteria in ‘Ca. Liberibacter asiaticus’-infected and uninfected citrus roots evidenced differences in the composition of their bacterial community (Trivedi et al., 2010). The influence of pathogen infection on endophytic bacterial community was also reported in healthy and phytoplasma-infected grapevine leaves (Bulgari et al., 2011).
Cultivation dependent methods allowed to isolate twelve colonies with different morphology from healthy roots and six colonies from infected roots. Sequences of the 16S rRNA gene identified Firmicutes of the genus Bacillus, Lysinibacillus and Paenibacillus; Gammaproteobacteria of the genus Pseudomonas. Six different Bacillus species were isolated from healthy apple trees and, among these, Bacillus amyloliquefaciens and Bacillus gibsonii were found also in infected plants. Interestingly, bacterial strains, here isolated, belong to genera widely studied for developing biocontrol strategies to contain plant pathogens. The endophytic bacteria isolated on culture media were characterized for five beneficial traits related to mineral nutrition (phosphate solubilization, siderophores, nitrogen fixation), development (indolacetic acid synthesis), stress relief (catalase activity), disease control (siderophores) in order to select some strains for in vivo biocontrol tests. These assays allow to select different strains belonging to the genus Pseudomonas and Lysinibacillus that showed biocontrol and plant-growth promotion abilities. Future studies will be carried out to investigate the activity of these endophytes to control apple proliferation.
Literature cited
BULGARI D., CASATI P., CREPALDI P., DAFFONCHIO D., QUAGLINO F., BRUSETTI L., BIANCO P.A. 2011 Restructuring of endophytic bacterial communities in grapevine yellows-diseased and recovered Vitis vinifera L. plants. Applied and Environmental Microbiology 77: 5018–5022.
DOYLE J.J., DOYLE J.L. 1990. Isolation of plant DNA from fresh tissue. Focus 12: 13–5
LUGTEMBERG B., KAMILOVA F. 2009. Plant-growth-promoting rhizobacteria. Annual Review of Microbiology 63: 541-556.
SMART C.D., SCHNEIDER B., BLOMQUIST C.L., GUERRA L.J., HARRISON N.A., AHRENS U., LORENZ K.H., SEEMÜLLER E., KIRKPATRICK B.C. 1996. Phytoplasma-Specific PCR Primers Based on Sequences of the 16S-23S rRNA Spacer Region. Applied and Environmental Microbiology 62: 2988–2993.
TRIVEDI P., SPANN T., WANG N. 2011. Isolation and characterization of beneficial bacteria associated with citrus roots in Florida. Microbial Ecology 62: 324–336
Scanning electron microscopy of thinned specimens: From multilayers to biological samples
No full textThe rules governing image formation of thin specimens in scanning and scanning transmission electron microscopy at low energy, deduced from the observation of semiconductor multilayers, were validated on specimens defined by a much more complex structure as the biological ones. It is shown that for a suitable specimen thickness it is possible to have, at the same time, backscattered electron images and scanning transmission electron images with a comparable resolution. Moreover, the nonconductive biological samples can be observed without charging effects if they are thin enough to ensure that a significant fraction of the electron beam crosses the specimen
T-Group
No full textFormazione degli adulti. Formazione professionale. Formazione manageriale. Formazione continua. Formazione a distanza. Autoformazione.Negli ultimi trent’anni la formazione non solo ha moltiplicato la sua presenza nei più differenti contesti organizzativi e istituzionali, ma ha anche ampliato notevolmente il suo orizzonte di disciplina e di attività destinata allo sviluppo di conoscenze, competenze, capacità. Lungo questo cammino la formazione ha saputo essere un luogo e un laboratorio per certi aspetti unico e privilegiato di sperimentazione e innovazione di metodologie didattiche, così da mutare profondamente e arricchire significativamente i nostri modi di pensare e costruire l’apprendimento. Questo volume si propone di presentare, per la prima volta nel nostro Paese, un ampio panorama di metodi formativi: da quelli più “classici” come la lezione e il role play a quelli più specificamente centrati sul gruppo e il lavoro di gruppo; da quelli ispirati dalle nuove tecnologie a quelli focalizzati sul cambiamento e lo sviluppo organizzativo; da quelli più personalizzati come il coaching e il counselling a quelli che coltivano l’ambizione di favorire e sostenere “la conoscenza e la cura di sé”. È dunque uno strumento indispensabile per tutti coloro che, a vario titolo, operano nel mondo della formazione: che la utilizzano e la offrono, la progettano e la realizzano
'Candidatus Phytoplasma phoenicium' associated with devastating diseases of stone fruits
No full text‘Candidatus Phytoplasma phoenicium’, taxonomic subgroup 16SrIX-B, was found in association with a lethal devastating almond disease (almond witches’-broom, AlmWB) in Lebanon in the early 1990s. It was later reported in Iran starting in 1995. During the last two decades, the outbreak of AlmWB has led to a rapid decline of almond trees in northern regions and in the Bekaa Valley in Lebanon and in Fars province and in other southern provinces in Iran. In 2009, ‘Ca. P. phoenicium’ was also identified in association with a severe disease of peach and nectarine in southern Lebanon. From 2012 to 2017, 'Ca. P. phoenicium' was found associated with apricot yellows and peach witches'-broom in Iran. The most characteristic symptoms in almond trees are shoot proliferation on the main trunk with the appearance of a witches’ broom, perpendicular development of many axillary buds with small and yellowish leaves, and general tree decline with final dieback. The presence of witches’-broom is more common in almond trees than in peach/nectarine, while phyllody was observed only in peach. A total loss of production happens 1–2 years after the initial appearance of the symptoms. In Lebanon, AlmWB epidemiological cycle involves Asymmetrasca decedens (prevalent in almond), possibly responsible for the transmission of ‘Ca. P. phoenicium’ from almond to almond, and cixiids of the genus Tachycixius (prevalent in Smilax aspera L. and Anthemis sp.), possibly responsible for the transmission from weeds to almond. In Iran, Prunus scoparia, a wild almond species harboring 'Ca. P. phoenicium', could play a role in the phytoplasma transmission pathways to fruit trees. Based on detection of 'Ca. P. phoenicium' in insect body and saliva and the presence of consistent populations, the leafhopper Frutioidea bisignata can be considered as potential vector of this phytoplasma in Iran. Alignment of 16S rDNA nucleotide sequences of 'Ca. P. phoenicium' strains from Lebanon and Iran allowed the identification of 21 SNPs mutually exclusive in the phytoplasma strain populations identified in the two countries. The combination of such SNPs allowed the recognition of nine SNP lineages in Lebanon and eight in Iran. Multiple gene typing analyses of ‘Ca. P. phoenicium’ strains infecting almond, peach, and nectarine in Lebanon allowed the identification of distinct AlmWB-associated phytoplasma strains from diverse host plants based on inmp (integral membrane protein) gene sequence analysis. This evidence suggests that AlmWB could be associated with phytoplasma strains derived from the adaptation of an original strain to diverse hosts. Healthy plant material and vector control are the main measures applied for AlmWB containment. The first report of a ‘Ca. P. phoenicium’ strain, identical to the species reference strain, on almond in Italy in 2019 opened a worrying scenario on its impact on production of stone fruits and other hosts
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