1,721,180 research outputs found
Association of phytoplasmas and viruses with malformed clovers
No full textPlants of Trifolium spp. exhibiting two different kinds of symptoms - phyllody associated with yellowing/reddening, and dwarf growth habit without floral abnormalities, were observed in several areas of the Czech Republic. Nested polymerase chain reaction (PCR) with phytoplasma specific primers, and restriction fragment length polymorphism (RFLP) analyses of 16SrDNA revealed that phyllody of T. repens was associated with phytoplasmas belonging to the 16SrI-C subgroup. Similar symptoms in T. hybridum and T. pratense plants revealed the presence of phytoplasmas belonging to two subgroups: 16SrI-C and 16SrIII-B. Dwarf disease of cultivated T. pratense plants was associated with more than one agent: eleven of twenty plants examined by PCR/RFLP analysis revealed the presence of phytoplasmas belonging to four distinct subgroups: 16SrI-B, 16SrI-C, 16SrIII-B and 16SrX-A. Moreover, two kinds of bacilliform virions were observed in ultrathin sections of fifteen T. pratense plants. Particles occurred mostly in the parenchymatous cells of vascular bundles and were located in the cytoplasm as aggregates within an extended network of membraneous cisternae. Phytoplasmas and rhabdoviruses occurred singly, and both together or in co-presence with filamentous virus-like particles
Three years of molecular monitoring of phytoplasma spreading in a plumgrowing area in Italy
No full textIn the plum growing area of Vignola (Northern Italy) a molecular monitoring was carried out in order to verify possibility to reduce the epidemic phytoplasma infection. Nucleic acids were extracted from plum leaf midribs for molecular tests to verify phytoplasma presence. Direct PCR using universal primer pairs P1/P7 followed by nested PCR with R16F2/R2 and specific primers R16(X)F1/R1 and RFLP analyses mainly with RsaI and SspI were employed to detect/identify phytoplasmas. The presence of phytoplasma specific DNA bands was observed after nested-PCR using either R16F2/R2 and R16(X)F1/R1 primers. From symptomatic and asymptomatic plum 16SrX-B phytoplasmas were identified. Four farms were monitored during 2000 testing 11 Japanese plum varieties: in June among 40 samples, all from symptomatic plants about 23% were positive in the first nested PCR reaction and 92% in the second one performed with group specific primers 16Sr(X)F1/R1. When the same plants were retested in October, 39 out of the 40 samples were positive in direct PCR. During July 2001 in two of the above farms a total of 57 asymptomatic plums were tested: in the first farm 21% of the plants tested were positive and in the second 17%. In July 2002 both symptomatic and asymptomatic plum were monitored in 3 different fields. Ten out of 20 samples from symptomatic plum resulted to be infected by 16SrX-B phytoplasmas, 5 were negative and in the other samples phytoplasmas belonging to groups 16SrXII-A, 16SrI-B and 16rIII-B were identified. Asymptomatic plant that were re-grafted in 2001 on rootstock where symptomatic scions were previous observed showed that 67% of the plant tested were infected by 16SrX-B phytoplasmas showing a clear evidence that the rootstock was colonized by the pathogens that are able to infect the new grafted scions just during one winter season
Detection and molecular characterization of a 16SrI-F phytoplasma in potato showing purple top disease in Ecuador
Full text linkPotato purple top (PPT) disease has been reported worldwide, including Canada, United States, Mexico, Russia and Pakistan. During surveys carried out in a recent epidemic in Ecuador of potato purple top disease phytoplasmas were identified in symptomatic potatoes as well as in some tissue cultured potato shoots by PCR/RFLP analyses and by sequencing and phylogenetic clustering. The majority of the samples resulted positive to phytoplasmas enclosed in the ribosomal subgroup 16SrI-F, for the first time detected in potato and in the American continent. Further studies will allow verification of the transmission and further presence in Ecuador of this phytoplasma associated with purple top disease of potatoes
Erigeron (Conyza) bonariensis, a host of ‘Candidatus Phytoplasma fraxini’-related strain in Brazil
Full text linkErigeron bonariensis, the flax-leaved fleabane is found in several regions of Brazil. In the State of Rio de Janeiro, plants of E. bonariensis exhibiting shortened internodes, reduced leaf size, witches’ broom and yellowing were tested for phytoplasma presence. Amplicons were obtained from nested PCR with primers designed for 16S rRNA and tuf genes. RFLP analyses of the ribosomal DNA revealed similarity to phytoplasmas of the ash yellows group and sequence analyses demonstrated 100% identity with phytoplasma strains belonging to subgroup 16SrVII-B from Argentina and Brazil. The sequence from tuf gene showed a maximum of 94% identity with ‘Candidatus Phytoplasma fraxini’ strain ASY3, and 92% identity with other strains of the ash yellows group. To our knowledge, this is the first report of the species Erigeron bonariensis harboring a ‘Ca. P. fraxini’-related strain in Brazil
Characterization of ‘Candidatus Phytoplasma asteris’ strains associated with periwinkle virescence in Southern Italy
Full text linkPhytoplasma symptomatology was observed in two periwinkle plants collected in a in commercial nursery in Campania Region (South Italy). The detected phytoplasmas were identified by RFLP analyses on amplicons and in silico as belonging to 16SrI-B subgroup (aster yellows). A multigene assays was performed to evaluate possible molecular diversity: the groEl gene characterization indicated that both strains are enclosed in subgroup groELI-III. The in silico RFLP analyses on tuf and rp genes allow to differentiate the two strains in periwinkle with Tsp509I endonuclease that produced unique profiles, clearly differentiating these from other phytoplasmas belonging to 16SrI-B subgroup. No differences were shown after RFLP analyses on SecY amplicons. Further work is in progress to evaluate the epidemiological relevance of these two aster yellows strains associated with virescence in periwinkle
Problemi fitopatologici della coltivazione del mirto
Full text linkMyrtus communisL., is mainly used in the food industry for the production of both a red
and a white traditional sardinian liquor. Given the important of this plant species for the
regional economy, many studies have been made to strenghten our knowledge on the different
cultivation techniques and on the potentiality of the different cultivars.
In the first part of this work a short review of the main Myrtle diseases is presented with
special enphasis nursery diseases induced byPhytophthorassp.,P. nicotinae, andP. italica,
and byCylindrocladium pauciramosumandC. scoparium, that seriously affect plant vitality .
Secondly we refer on a severe series of symptoms, observed during recent experimental
surveyes carried out in Northen Sardinian, and apparently related to phytoplasma infections.
Here we describe our studies aimed to assess the phytoplasmas presence on the lives of
symptomatic plants collected from two different fields. A series of molecular assays with
PCR and nested-PCR followed by RFLP allowed to identify the presence of 16SrIII-B
phytoplasma (reference strain “Peach X disease”), 16SrX-A subgroup (reference strain
“Apple proliferation”) and 16SrXII-A (reference strain “Stolbur”) in the plant samples.
Epidemiological role of the plant material used for myrtle propagation and of theAuchenorrynchapopulations present in the field, are discussed, as well as, disease control
Spreading of ESFY phytoplasmas in stone fruit in Catalonia (Spain)
No full textA survey was carried out in nine stone fruit commercial
orchards located in Barcelona province where
plum and apricot trees of different cultivars showing
European stone fruit yellows (ESFY) symptoms were
present. A 4-year survey with visual inspection of
symptoms in one apricot orchard showed a rather high
ESFY disease spread, also in a Japanese plum plantation
newly infected plants were detected every year in
a similar rate (about 2%). All the inspected symptomatic
trees were polymerase chain reaction (PCR) tested
and ESFY phytoplasma identity was confirmed by
restriction fragment length polymorphism analyses and
sequencing of ribosomal DNA amplification products.
In apricot plantation the detection of ESFY phytoplasma
was also tested on 69 asymptomatic trees sampled
in summer 2002. The nested PCR with 16SrX groupspecific
primers allowed detection of ESFY phytoplasmas
in 50% of the trees that indeed showed symptoms
by the next winter (2003). The molecular detection of
ESFY phytoplasma in asymptomatic apricot trees indicates
the risk of maintaining phytoplasma foci in the
fields where eradication is based only on visual inspection
Molecular and biological characterization of phytoplasmas from coconut palms affected by the lethal yellowing disease in Africa
No full textCôte d'Ivoire lethal yellowing (CILY) is a devastating disease associated with phytoplasmas and has recently rapidly spread to several coconut-growing areas in the Country. Phytoplasmas are phloem-restricted bacteria that affect plant species worldwide. These bacteria are transmitted by plant sap-feeding insects, and their cultivation was recently achieved in complex artificial media. In this study, phytoplasmas were isolated for the first time from coconut palm trunk borings in both solid and liquid media from CILY symptom-bearing and symptomless coconut palms. The colony morphology, PCR and sequencing analyses indicated the presence of phytoplasmas from different ribosomal groups. This study reports the first biochemical characterization of two of these phytoplasma isolates. Moreover, a disc-diffusion antibiotic susceptibility assay revealed that these bacteria exhibit tobramycin susceptibility and cephalexin hydrate and rifampicin resistance. Urea and arginine hydrolysis, and glucose fermentation tests that were performed on colonies of phytoplasmas and Acholeplasma laidlawii indicated that both phytoplasmas tested were negative for urea and positive for glucose and arginine, whereas A. laidlawii was positive for glucose and negative for urea and arginine. The growth of coconut phytoplasmas in both solid and liquid artificial media and the biological characterization of these isolates are novel and important advancements in the field of disease management and containment measures for the CILY disease. The characterization of isolated phytoplasmas will allow for more efficient management strategies in both the prevention of a coconut phytoplasma epidemics and the reduction of the economic impact of the disease in the affected areas
STRATEGIA DI DIFESA FITOSANITARIA DELLE SPECIE OFFICINALI PER UNA MAGGIORE VALORIZZAZIONE DELLA PRODUZIONE ERBORISTICA LEGATA AL TERRITORIO
No full textI maggiori produttori di piante officinali sono in Europa sono Ungheria, Polonia, Bulgaria, Francia, Belgio ed Olanda. Negli ultimi 15 anni anche in Italia è aumentata sensibilmente la richiesta di piante officinali da parte di industrie farmaceutiche, cosmetiche ed erboristerie a seguito di una maggiore consapevolezza ed attenzione del “consumatore” nei confronti di sostanze naturali e prodotti biologici. La crescente richiesta di specie officinali (medicinali ed aromatiche) ha determinato un aumento sensibile delle superfici coltivate, insufficiente però a soddisfare la domanda interna. Continua quindi ad essere necessario importare materiali vegetali (piante intere e/o parti di pianta) che, pur essendo molto competitivi dal punto di vista economico, sono purtroppo nettamente inferiori a quelli nazionali in termini di qualità sanitaria.
La produttività degli impianti e la qualità delle droghe vegetali sono, infatti, spesso minacciate da fitopatie epidemiche, quali fitoplasmosi e virosi, in grado di compromettere la resa degli impianti, così come di modificare qualitativamente e quantitativamente i principi attivi che costituiscono la droga. Il risultato è un prodotto di qualità scadente.
L’aspetto sanitario delle coltivazioni occupa quindi un ruolo importante nell’economicità degli impianti e nella standardizzazione del prodotto finale destinato al consumo diretto od alla trasformazione industriale. Da qui l’interesse nel valutare l’incidenza delle malattie dovute a virus ed a fitoplasmi in coltivazioni di piante medicinali ed officinali site nel Comune di Sogliano sul Rubicone (Forlì-Cesena), zona collinare sui crinali dell’Appennino Tosco-Marchigiano a 379 metri s.l.m. con lo scopo di indicare la profilassi da adottare per prevenire l’insorgere di queste malattie e valorizzare nostra la produzione erboristica.
Durante numerosi sopralluoghi eseguiti nel triennio 2004-2007, sono stati ispezionati diversi appezzamenti raccogliendo campioni vegetali (foglie e/o fiori) con sintomi attribuibili alla presenza di virus e/o fitoplasmi. Sono state esaminate le seguenti specie: Hyssopus officinalis L. caratterizzato da giallume fogliare, virescenza e nanismo; Galega officinalis L. con sintomi di giallume e nanismo; Salvia sclarea L. caratterizzata in alcuni casi da mosaico giallo oro sulle foglie e nanismo, in altri da giallume; Parietaria officinalis L. e P. judaica Auct. An. L., entrambe mostranti sintomi di giallume e nanismo. Per verificare la presenza di eventuali infezioni da virus sono state eseguite prove di trasmissione meccanica e saggi immunoenzimatici applicando la tecnica PAS-ELISA. Per quanto riguarda la diagnosi per la presenza di fitoplasmi, sono state applicate le tecniche PCR e RFLP.
Le specie esaminate sono risultate infette da fitoplasmi appartenenti prevalentemente al gruppo 16SrXII (stolbur), considerato “ubiquitario” sia in Italia che in Europa ed individuato in piante erbacee ed arboree (pomodoro, patata, fruttiferi e vite) ove è in grado di provocare anche forti epidemie e da 2 virus: BBWV e AMV
Identification and Molecular Characterization of Multiple Phytoplasma Infection in Spartium Junceum and Cytisus Scoparius
No full textTwo genera of the Fabaceae family showed phytoplasma symptoms in Germany and in Italy. Spartium junceum showing typical SpaWB symptoms was observed in the city of Ercolano (Campania region, Italy) and a similar symptomatology was observed in a group of shrubs of Cytisus scoparius growing in Dahlem botanical garden in Berlin (Germany). Symptomatic and asymptomatic samples were collected in both cases and analysed for phytoplasma presence by nested-PCR assays followed by RFLP analyses. All symptomatic samples produced amplicons of the expected lengths and no product was amplified from asymptomatic plants. Identification and classification of phytoplasmas allowed to detect ‘Candidatus Phytoplasma spartii’ subgroup 16SrX-D and ‘Ca. P. asteris’ subgroup 16SrI-B in both genera. In some of the samples of C. scoparius also stolbur phytoplasmas were identified
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