1,721,677 research outputs found
Tropicsafe project: Detection and management of lethal yellowing and grapevine yellows diseases in partner countries
No full textThe confirmation of the presence of 16SrXXII-B phytoplasmas associated with coconut lethal yellowing disease in Ghana and of 16SrIV in the Caribbean (Jamaica, Cuba, and Mexico) were the basis to study alternative plant species and potential insect vectors of this economically relevant disease carried out by the TROPICSAFE project started in 2017. In South Africa grapevine yellows disease associated with ‘Candidatus Phytoplasma asteris’, (subgroup 16SrI-B) and transmitted by the leafhopper Mgenia fuscovaria was studied in its main epidemiological aspects that are relevant to its management. In Chile and in Italy phytoplasmas belonging to diverse ribosomal subgroups and several alternative host plants were detected. Some insect species have been described as phytoplasma vectors or potential vectors in grapevine or in vineyard environments
Giallumi della vite
No full textDescrizione dei giallumi della vite dovuti a fitoplasmi ed in particolare di flavescenza dorat
Grapevine phytoplasmas a 2014-2108 update
Full text linkGrapevine yellows (GY) are often associated with molecularly differentiable phytoplasmas according to their geographic distribution and sometimes also to different varieties. A review of the most recent findings worldwide is presented
La flavescenza dorata in Europa ed in Italia: aggiornamenti scientifici
No full textIncontro sulla flavescenza dorata della vite tenutosi a Verona a gennaio 2024
Fruit trees and phytoplasmas: a well settled association
No full textThe discovery, just fifty year ago, of a new group of plant pathogens related to bacteria led to the finding of polymorphic prokaryotes, located in the phloem of many plant species affected by yellows-type diseases believed to be caused by viruses, considering their infectious nature, and transmission by insects. The first retrievable records of phytoplasma related symptoms in fruit trees were presented during the first ICVF meeting (1954) when these pathogens were not know. In the last years molecular data have provided considerable insights into phytoplasma molecular diversity, and genetic interrelationships; significant taxonomic progress has been achieved by the study of the 16S ribosomal gene and other conserved genes allowing designation of 33 ribosomal groups and 41 ‘Candidatus Phytoplasma’ species. However, there is a gap between taxonomy and diseases since it is not uncommon that the same disease is associated with molecularly differentiable phytoplasmas, and with more than just one phytoplasma especially in woody host plants. Full sequencing of genomes of five phytoplasmas and a number of draft sequences provided the knowledge about putative biochemical pathways, confirming that phytoplasmas are very special microorganism lacking relevant bacterial features such as cell wall, mobility, key enzymes and pathways. They appears to have a small efficient chromosome and tricky metabolisms, allowing them to a trans kingdom life of interaction that often increase activity of their hosts such as enhancing insect fitness, plant shoot production, morphology and plant life cycles. They seems to preparing to become permanent cell hosts; however they are still far from loose independence and freedom as can also act as very dangerous pathogens. Epidemiologic studies of phytoplasma-associated diseases allow confirming the possibility to molecularly identify strains that have the most important roles in fruit tree disease outbreaks. These diseases are mainly widespread presence Europe and include apple proliferation, pear decline, and European stone fruit yellows tentatively classified as ‘Ca. P. mali’, ‘Ca. P. pyri’ and ‘Ca. P. prunorum’, all belonging to ribosomal group 16SrX. Apple proliferation, only reported in Europe is one of the most important disease of this species reducing size, weight and quality of fruit. Although it affects most or all varieties of apple, it is associated with relatively genetically homogeneous phytoplasmas and vectored by the psyllids Cacopsylla picta, C. melanoneura and the leafhopper Fieberiella florii. Pear decline, firstly reported in western USA and Canada, is of relevant importance in European pear orchards and was recently identified also in South Amrica. Main symptoms enclose poor shoot and spur growth, dieback, premature reddening and upper rolling of leaves, reduced leaf and fruit size and number. Insect vectors are C. pyricola and C. pyri. European stone fruit yellows is a disease seriously affecting apricot, plum, and peach; apricot and Japanese plum. Although symptom severity is fairly variable, infected trees show typical yellows accompanied by leaf roll followed by leaf reddening, and often winter sprouting. ‘Ca. P. prunorum’ vectored by C. pruni is the associated organism, together with some other phytoplasma among which the “stolbur” (‘Ca. P. solani’, 16SrXII-A) is very often present. Severe epidemic of ‘Ca. P. phoenicium (16SrIX) are also recently reported in some areas of the Arabian peninsula.
The phytoplasma growth in artificial media achieved from periwinkle shoots and from field infected plants should allow the confirmation of the molecular information on phytoplasma biology and possibly pathogenicity gained in the last years. This knowledge will help in defining feasible solutions to reduce the phytoplasma disease impact and in devising the best management strategies, especially in fruit tree crops considering their several years’ permanence in orchards
Phytoplasmas and plant diseases: a transkingdom relationship
No full textPhytoplasmas or ‘Candidatus Phytoplasma’ are bacteria without cell wall living only in the insect hemolymph and in the plant sieve tubes. After more than 20 years from their discovery their role as plant pathogens is still not resolved for lack of Koch postulates fulfillment. Worldwide there are several relevant epidemics in which phytoplasmas play a role as key factors in reducing the production and the revenues of crops. This situation is worsen by their dissemination by propagation and micropropagation materials, insect vectors, and seeds. Economically relevant phytoplasma diseases are reported in both woody and annual crops since these bacteria are present in several diverse environments and in particular in tropical and subtropical areas where the insect vectors play their dissemination to alternate plant and insect host species. There are a number of phytoplasma metabolic features and effectors that were discovered mining several available full and draft genomes that are clarifying the interactions of these bacteria with both plants and insect vectors confirming their two kingdoms adaptation ability. Recent efforts allowed to obtain colonies containing mainly phytoplasmas following their isolation from field-infected or experimentally-infected plants. Moreover, little steps are in progress to define direct phytoplasma biological activity while several pathogenicity related factors were found and confirmed as potentially active in transgenic plants. Molecular tools helped in resolving phytoplasma differentiation and allowed to study their epidemiology for appropriate and environmentally friendly management of associated diseases, moreover their isolation in artificial media should help in clarifying their phytopathological role in severe epidemics worldwide such as coconut lethal yellowing and grapevine yellows
Fitoplasmas asociados a rnfermedades en cultivos de frutales tropicales y subtropicales/Phytoplasmas associated to diseases in tropical and subtropical fruit crops
No full textThe discovery, just fifty year ago, of a new group of plant pathogens related to bacteria led to the finding of polymorphic prokaryotes, located in the phloem of many plant species affected by yellows-type diseases believed to be caused by viruses, considering their infectious nature and transmission by insects. Phytoplasmas lack relevant bacterial features such as cell wall, mobility, key enzymes and pathways nevertheless they have tricky metabolisms allowing them to a trans kingdom life of interaction between plant and insects therefore the tropical and subtropical environments are those providing major survival and evolution possibility for them. In the last years molecular data have provided considerable insights into phytoplasma molecular diversity, and genetic interrelationships; significant taxonomic progress has been achieved by the study of the 16S ribosomal gene and other conserved genes allowing designation of 33 ribosomal groups and 41 ‘Candidatus Phytoplasma’ species. However while a restricted number of such pathogens appears to be associated with phytoplasma diseases in fruit crops in temperate areas, an increasing number of phytoplasma strains are detected and associated, alone or in association with other pathogens in tropical and subtropical fruit crops. Severe phytoplasma-associated epidemic were reported in citrus, coconut, papaya, litchi and longan, and phytoplasma presence was occasionally detected in mango, banana, pineapple, macadamia and passion fruit. In some of these species such as coconut in America and Africa the presence of specific phytoplasmas belonging to groups 16SrIV and 16SrXXII was reported. However other ribosomal groups / ’Candidatus Phytoplasma’ species were detected in this and the other species (16rI, 16SrII, 16SrV, 16SrIX, and 16SrXII). The recent progress made in phytoplasma identification and molecular characterization together with the implementation of their growth in artificial media will help in devising management strategies aimed to reduce environmental impact of phytoplasma disease containment measures also trough international projects targeting tropical and subtropical areas such as the EU financed TROPICSAFE
‘Candidatus Phytoplasma aurantifolia’ and ‘Candidatus Phytoplasma australasia’: epidemiology meets quarantine
No full textThe use of ‘Candidatus Phytoplasma’ as provisional taxon is helping both epidemiological studies and quarantine rules settling.
A focused search in database evidences discrepancies and problems for strains enclosed in ‘Ca. P. aurantifolia’ and ‘Ca. P.
australasia’ that share very often the same geographic distribution in Asian and Australian countries. An improved
differentiation based on multigene approach could be useful to a more clear distiction of these phytoplasma strains
Foreword of Phytoplasma Diseases in Asian Countries
No full textPhytoplasma III is the last one of three books covering the aspects related to phytoplasma-associated diseases. These diseases are limiting the quality and productivity of economically important agriculture crops worldwide and are especially relevant in Asian countries. Their management options are focused on minimizing their spread by insect vectors and propagation materials and on development of host plant resistance. Annual losses due to phytoplasma diseases may vary, but under the pathogen favorable condition, phytoplasma disease may lead to disastrous consequences for farming and industry community. The phytoplasma associated plant diseases were first detected in China during the Song dynasty (960-1227 CE) on green peonies, but important scientific progress about the identification of phytoplasmas only began after 1980’s after they discovery carried out in Japan in 1967. Significant advancement in the last decades on biological and molecular properties, epidemiology, host-pathogen-insect interactions as well as management of phytoplasma-associated diseases has been made. The book is enclosing updated information on phytoplasmas, and phytoplasma-associated diseases focused on the Asian countries and provides comprehensive information on recent approaches for diagnostics, transmission, and management aspects. This volume contains 12 chapters contributed by experienced scientist working in Asian countries on different aspects of phytoplasma-associated diseases. These chapters cover novel methods for phytoplasma detection and available information about graft transmission, insect vector transmission with emphasis on citrus crops. The addition of chapters dedicated to the management of these disease by controlling their insect transmission and eliminating phytoplasmas from infected plants providing relevant information for the agricultural operators and farmers. The role of quarantine in phytoplasma diseases containment is also presented and focused on the Asian countries situation. Genomic studies that started in Japan with the fist sequence of a phytoplasma published in 2004, are summarized and updated with the Asian based experience on pathogenicity factors and possible mechanisms of interaction with plants enclosing plant resistance to phytoplasma-associated diseases. The information on various topics is advanced and comprehensive, provides appropriate information to everyone interested in phytoplasmas and their associated disease management. The book serve as an exhaustive and up-to-date compendium on various aspects of phytoplasmas affecting important crops in Asian countries.
Although phytoplasmas remain the most poorly characterized plant pathogens, the presentation of the knowledge acquired in area of the world will allow reducing the incidence and the losses due to these pathogens in the Asian agriculture also reducing the impact and worldwide spreading of phytoplasma-associated diseases
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