1,720,983 research outputs found
Electron microscopy and molecular identification of phytoplasmas associated with strawberry green petals in the Czech Republic
No full textThe presence of phytoplasma in Fragaria ananassa x Duch cv Senga Sengana showing strawberry green petals symptoms was observed by electron microscopy of phloem tissue. No phytoplasmas were found in asymptomatic strawberry plants used as controls. Nucleic acids extracted from these plants were used in nested-PCR assays with primers amplifying 16S rRNA sequences specific for phytoplasmas. Bands of 1.2 kb were obtained and the subsequent nested-PCR with specific primers and RFLP analyses allowed to classify the detected phytoplasmas in the aster yellows group (16SrI). They belonged to the subgroup I-C of which type strain is clover phyllody phytoplasma
Identification of phytoplasmas associated with a decline of European hackberry (Celtis australis)
No full textThe presence of phytoplasmas in declining trees of European hackberry was demonstrated for the first time using polymerase chain reaction assays with primers amplifying phytoplasma 16S rDNA regions. Restriction fragment length polymorphism analysis of these DNA fragments together with PCR, employing primers specific for particular phylogenetic groups of phytoplasmas, made it possible to detect the presence of aster yellows group (16SrI) related phytoplasmas. These were classified into two different subgroups (I-B and I-C) and were present in both symptomatic and asymptomatic hackberry plants. Aster yellows-related phytoplasmas were found in all the root samples collected during the winter. In addition, phytoplasmas from the peach X disease group (16SrIII) were found in four out of 10 root samples; in five root samples phytoplasmas of the elm yellows group (16SrV) were also present
Molecular detection of phytoplasmas in apple with rubbery wood symptoms
No full textRubbery wood is a severe disease which affects both apple and pear trees and may cause severe losses in some countries. The affected plants show a partial lack of lignification of young branches which gives the plant a typical prostrate appearance. In longitudinal sections of flower petioles and green prebursted shoots from grafts or diseased trees, strong fluorescent areas associated with DNA due to phytoplasmas or to other infectious agents were observed using fluorescent microscopy-DAPI technique. Round structures resembling phytoplasmas were also observed under the scanning electron microscope. Further analyses were performed to verify the presence of phytoplasma and allow their molecular identification. Samples from two source plants from the Czech Republic and one from Canada were employed in direct and nested polymerase chain reaction assays together with apple proliferation samples and group specific control phytoplasma strains as positive controls. General ribosomal primer pairs employed were R16F1/R0 and R16F2/R2, while group-specific primer pairs were R16(I)F1/R1, R16(III)F2/R1, R16(V)F1/R1 and R16(X)F1/R1. A DNA fragment of 1.2 kb was produced from some of the rubbery wood samples and from apple proliferation samples as well as from the positive controls when nested PCR was carried out with the primer pair R16F2/R2. The amplification with specific primers yielded a 1.1 kb fragment from the rubbery wood samples amplified using primer pairs R16(I)F1/R1. RFLP analysis confirmed that phytoplasmas that belong to the aster yellows group (16SrI) were present. PCR experiments with primers that amplify a chromosomal portion of aster yellows group phytoplasmas followed by Southern hybridization with the homologous DNA probe confirmed the presence, in some of the apple rubbery wood samples, of phytoplasma that belong to the aster yellows group
Detection of multiple phytoplasmas in perennial fruit trees with decline symptoms in Italy
No full textNested polymerase chain reaction assays with two universal and four phytoplasma (formerly called mycoplasmalike organism) 16S rRNA group-specific primer pairs were employed to investigate etiologies of diseases associated with pear (decline), plum (leptonecrosis), nectarine (chlorotic leaf roll), and apricot (chlorotic leaf roll and decline) fruit crops grown in northern Italy. Restriction fragment length polymorphism analyses of phytoplasma 16S rDNA sequences amplified with various combinations of these primer pairs revealed that two to four distinct types of phytoplasmas affiliated with phytoplasma 16S rRNA group I taster yellows phytoplasma and related strains), group III (peach X-disease and related phytoplasmas), group V (elm yellows phytoplasma and related strains), and group X (apple proliferation and related phytoplasmas) were associated with most diseases. Predominant phytoplasma strains associated with pear decline, apricot chlorotic leaf roll, and plum leptonecrosis were identified as members of group X (subgroups A and B). Phytoplasma strains associated with nectarine chlorotic leaf roll were members of group I. Minor phytoplasma strains (one or more distinct types) were also detected in each infected plant, except for those affected by apricot decline
Phytoplasmas, Aceria bezzii and drought in declining European hackberry (Celtis australis L.)
No full textGrowth abnormalities and decline of hackberry trees have been reported throughout the Mediterranean growth area of the species for over 50 years. Recently, the presence of phytoplasmas belonging to aster yellows and elm yellows groups was detected by molecular techniques in both declining and asymptomatic hackberries. Symptoms of decline appear to be influenced by the amount of rainfall during early spring. In Italy hackberry trees are also infested by the eriophide mite Aceria bezzii (Corti) which kills most of the main, fertile buds causing delayed sprouting of adventitious, sterile buds and loss of fruit production. These three factors seem to interact in determining the sanitary status of this Ulmacea. The widespread phytoplasma presence seems to insidiously weaken trees, which clearly show stress symptoms in drought years, whereas mite infestation acts beneficiously on tree health by reducing the number of sprouting buds and fruit-set, and delaying burst of adventitious buds
Molecular identification and seasonal monitoring of phytoplasmas infecting Croatian grapevines
No full textPhytoplasmas of the 16S rRNA RFLP group XII-A (stolbur) have been detected with tests carried out 4 times from September 1997 to April 1998 in Croatian Pinot gris grapevines showing yellows symptoms. This is the first report on the presence of stolbur phytoplasma in Croatian grapevines. Two asymptomatic vineyard weeds, Taraxacum officinale Web. and Polygonum lapathifolium L. showed the presence of the same prokaryotes
Identification of phytoplasmas in eggs, nymphs and adults of Scaphoideus titanus Ball reared on healthy plants
No full textA survey for the presence of aster yellows-related phytoplasmas in the different life stages of Scapholdeus titanus was carried out by means of PCR and nested-PCR assays. Using a phytoplasma 16Srl group-specific primer pair followed by RFLP analysis of amplified products, we were able to detect and identify phytoplasmas from eggs, newly hatched nymphs, fourth and fifth instar nymphs and adults reared on ten phytoplasma-free Vicia faba seedlings. Two of these bread beans became infected, whereas PCR failed to detect phytoplasmas in the same ten plants before leafhopper rearing. These results suggest the possibility of transovarial transmission of aster yellows-related phytoplasmas in S. titanus
Prima segnalazione di Pestalotiopsis spp. su nocciolo in Italia.
No full textItaly is the first European producer of hazelnuts (Corylus avellana L.) and second in the world after Turkey. The orchards are mainly located in Piedmont, Lazio, Campania and Sicily.
In 2013 a sample of hazelnut leaves from Piedmont, showing necrotic spots, has been analyzed.
The aims of this work have been to identify the causal agent and verify Koch's postulates, since specific references in literature are not present.
Colonies with a white aerial, dense mycelium with black acervuli close to center, similar to ink drops, grew really fast from hazelnut leaf samples plated on PDA.
At light microscope the conidia appeared ellipsoid 4-septate, with three brown central cells, the basal and apical cells hyaline and with appendages. Morphologically the fungus was identified as Pestalotiopsis spp. Molecular identification has still not been successfully applied for species-level differentiation. Furthermore pathogenicity tests on leaves, both in vitro and in vivo, were set up at different temperatures. Positive response and a better infection resulted at 20°C. Pestalotiopsis was reisolated from the leaf tissues artificially infected.
Pestalotiopsis spp. on hazelnut has been reported in different countries, in particular P. macrospora was found to be pathogenic on leaves and twigs in İran and P. guepinii in Turkey. Furthermore in 2015 Pestalotiopsis spp. was reported to cause disease on halzenut fruit clusters in Turkey, causing yield reduction.
This work is the first report of Pestalotiopsis in hazelnut in Italy. Due to the economic importance of this crop in Italy, the incidence of this fungus should be monitored
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