Bois noir is the most widespread phytoplasma grapevine disease in Europe. It is associated with '
Phytoplasma solani', but molecular interactions between the causal pathogen and its host plant are ...not well understood. In this work, we combined the analysis of high-throughput RNA-Seq and sRNA-Seq data with interaction network analysis for finding new cross-talks among pathways involved in infection of grapevine cv. Zweigelt with '
. P. solani' in early and late growing seasons. While the early growing season was very dynamic at the transcriptional level in asymptomatic grapevines, the regulation at the level of small RNAs was more pronounced later in the season when symptoms developed in infected grapevines. Most differentially expressed small RNAs were associated with biotic stress. Our study also exposes the less-studied role of hormones in disease development and shows that hormonal balance was already perturbed before symptoms development in infected grapevines. Analysis at the level of communities of genes and mRNA-microRNA interaction networks revealed several new genes (e.g., expansins and cryptdin) that have not been associated with phytoplasma pathogenicity previously. These novel actors may present a new reference framework for research and diagnostics of phytoplasma diseases of grapevine.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Hyalesthes obsoletus (Hemiptera: Fulgoromorpha: Cixiidae) is a pan-European polyphagous planthopper known as a significant vector of the plant pathogenic bacterium ?Candidatus Phytoplasma solani? ...(stolbur phytoplasma), which poses threats to various agricultural crops. A population of H. obsoletus associated with Convolvulus arvensis in Serbia was studied to investigate the presence and genetic diversity of Wolbachia, an endosymbiotic bacterium known for its promising biological control applications. Both insect-associated microorganisms, ?Ca. P. solani? and Wolbachia, were found in the assessed H. obsoletus population. The analyzed vector population had a ?Ca. P. solani? infection rate of 50%, while Wolbachia showed a high infection rate of 80%. Wolbachia presence displayed minimal variation across genders and was independent of individuals? phytoplasma-infection status. Genotyping of the identified ?Ca. P. solani? strains revealed four previously described stamp genotypes (Rqg50/St1, Rqg31/St2, STOL/St4 and M5/St28). Notably, a single novel Wolbachia ftsZ genotype, designated WHo1, was found in the assessed H. obsoletus population, providing a valuable insight into the genetic diversity of Wolbachia endosymbionts within the Cixiidae family. Phylogenetic analysis demonstrated intricate relationships between WHo1 and other Wolbachia strains infecting hosts from diverse hemipteran suborders. Although Wolbachia-based strategies show promise for phytoplasma vector control, further research is needed to elucidate its potential interactions with ?Ca. P. solani? and its effects on vector reproduction and fitness.
‘Candidatus Phytoplasma solani’ (CaPsol) is a very common pathogen in the Euro-Mediterranean regions and has been reported in many countries. Field surveys were conducted in tomato plantations in ...2022 to determine the CaPsol infections in the western part of Turkey, which has the highest vegetable production volume. A total of 67 tomato samples, 52 symptomatic and 15 asymptomatic, were collected from four different provinces. A total of thirteen CaPsol strains were identified using molecular techniques from tomato samples. The tuf/stamp/vmp1 genes molecular markers were used to perform molecular and genetic diversity characterizations of these strains. The tuf-b1 genotype and five different stamp genotypes genetically closely related to Eastern European strains were determined in all strains. In addition, these strains showed more than 99% nucleotide sequence similarity with 4 different vmp1 genotypes: V2-TA, V14, V4, and V15. Advanced bioinformatics analyses were performed with stamp (N = 290) and vmp1 (N = 207) strains obtained from this study and GenBank. These analyses showed that the strains for both gene regions descended from two molecular evolutionary ancestors. In order to calculate the genetic distance relationships according to the stamp and vmp1 gene regions, a hierarchical classification was done as geographical and host populations. While these analyses demonstrate the close genetic relationship between Turkish and Eastern European populations, they strongly confirm the importance of the epidemiological cycle between weed, perennial, and insect vectors. Then, molecular variance analyses (AMOVA) were performed on these classified populations. The results indicated high variation for both gene regions but showed that each strain contributed greatly to the CaPsol genetic diversity. Thus, for the first time, multilocus sequence patterns of CaPsol strains obtained from western Turkey were extracted. Extensive genetic analyses have strongly demonstrated the importance of horizontal transmission in the control and epidemiological cycle of CaPsol.
•For the first time, tuf/stamp/vmp1 gene patterns of tomato ‘Ca. P. solani’ strains were determined in tomato plantations of Western Turkey.•Bioinformatic analyses indicated that ‘Ca. P. solani’ strains have a very high genetic diversity.•Phylogenetic analyses based on the stamp and vmp1 gene regions showed that the strains evolved from two major clades.•Results strongly supported the hypothesis that population dynamics of ‘Ca. P. solani’ could be shaped by insect vectors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The pathogenicity of intracellular plant pathogenic bacteria is associated with the action of pathogenicity factors/effectors, but their physiological roles for most phytoplasma species, including ‘
...Candidiatus
Phytoplasma solani’ are unknown. Six putative pathogenicity factors/effectors from six different strains of ‘
Ca
. P. solani’ were selected by bioinformatic analysis. The way in which they manipulate the host cellular machinery was elucidated by analyzing
Nicotiana benthamiana
leaves after
Agrobacterium
-mediated transient transformation with the pathogenicity factor/effector constructs using confocal microscopy, pull-down, and co-immunoprecipitation, and enzyme assays. Candidate pathogenicity factors/effectors were shown to modulate plant carbohydrate metabolism and the ascorbate–glutathione cycle and to induce autophagosomes. PoStoSP06, PoStoSP13, and PoStoSP28 were localized in the nucleus and cytosol. The most active effector in the processes studied was PoStoSP06. PoStoSP18 was associated with an increase in phosphoglucomutase activity, whereas PoStoSP28, previously annotated as an antigenic membrane protein StAMP, specifically interacted with phosphoglucomutase. PoStoSP04 induced only the ascorbate–glutathione cycle along with other pathogenicity factors/effectors. Candidate pathogenicity factors/effectors were involved in reprogramming host carbohydrate metabolism in favor of phytoplasma own growth and infection. They were specifically associated with three distinct metabolic pathways leading to fructose-6-phosphate as an input substrate for glycolysis. The possible significance of autophagosome induction by PoStoSP28 is discussed.
Bois noir, a disease of the grapevine yellows complex, is associated with 'Candidatus Phytoplasma solani' and transmitted to grapevines in open fields by the cixiids Hyalesthes obsoletus and Reptalus ...panzeri. In vine-growing areas where the population density of these vectors is low within the vineyard, the occurrence of bois noir implies the existence of alternative vectors. The aim of this study was to identify alternative vectors through screening of the Auchenorrhyncha community, phytoplasma typing by stamp gene sequence analyses, and transmission trials. During field activities, conducted in Northern Italy in a vineyard where the bois noir incidence was extremely high, nine potential alternative insect vectors were identified according to high abundance in the vineyard agro-ecosystem, high infection rate, and harbouring phytoplasma strains characterized by stamp gene sequence variants found also in symptomatic grapevines. Transmission trials coupled with molecular analyses showed that at least eight species (Aphrodes makarovi, Dicranotropis hamata, Dictyophara europaea, Euscelis incisus, Euscelidius variegatus, Laodelphax striatella, Philaenus spumarius, and Psammotettix alienus/confinis) are alternative vectors of 'Candidatus Phytoplasma solani' to grapevines. These novel findings highlight that bois noir epidemiology in vineyard agro-ecosystems is more complex than previously known, opening up new perspectives in the disease management.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Among grapevine yellows, Bois noir (BN), associated with '
Phytoplasma solani', represents the biggest threat in the main wine-growing areas worldwide, causing significant losses in berry quality and ...yields. BN epidemiology involves multiple plant hosts and several insect vectors, making considerably complex the development of effective management strategies. Since application of insecticides on the grapevine canopy is not effective to manage vectors, BN management includes an integrated approach based on treatments to the canopy to make the plant more resistant to the pathogen and/or inhibit the vector feeding, and actions on reservoir plants to reduce possibilities that the vector reaches the grapevine and transmit the phytoplasma. Innovative sustainable strategies developed in the last twenty years to improve the BN management are reviewed and discussed.
Bois noir (BN) disease of grapevine is associated with ‘Candidatus Phytoplasma solani’ (CaPsol). Due to its multifaceted ecology, BN control is extremely difficult. Several studies showed that BN ...recovery can be elicited by abiotic stresses and treatment with resistance inducers. In this study, field trials along with molecular analyses have been conducted to evaluate if grafting of recovered shoots can increase the BN recovery rate in symptomatic grapevines and decrease the new CaPsol infection rate on asymptomatic grapevines. Field trials were performed in two vineyards (cv. Chardonnay/Kober 5BB) in Franciacorta (Lombardy Region, northern Italy). Grafting effects were evaluated by symptom observation and CaPsol detection by nested-PCR stamp gene amplification for three consecutive years and compared with non-grafted control vines. Obtained data showed that BN incidence was lower in grafted plants, mainly due to a statistically significant increase of recovery rate, four times higher than in non-grafted plants. These data indicated that grafting of recovered shoots can efficiently induce BN recovery, opening an interesting scenario for its utilization in sustainable strategies of vineyard management.
•Grafting of recovered shoots is highly efficient.•Grafting of recovered shoots drastically decreases bois noir incidence.•Grafting of recovered shoots significantly increases BN recovery rate but does not affect new bois noir infection rate.•Grafting can be a useful procedure for long-term BN management.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
During field surveys conducted in 2020 in Jordanian orchards, phytoplasma‐like symptoms (leaf yellowing/reddening and rolling, and witches'‐broom) were observed in three stone fruit species (peach, ...European plum, sweet cherry) and persimmon. Molecular analyses identified phytoplasma strains belonging to the species ‘Candidatus Phytoplasma solani’ (subgroup 16SrXII‐A) as largely prevalent in stone fruit and persimmon symptomatic plants. Moreover, ‘Ca. Phytoplasma omanense’ (16SrXXIX‐B) was found in few European plum symptomatic plants. In previous studies, such phytoplasma strains were identified in other important crops (almond, pomegranate, and grapevine) and in several putative insect vectors, suggesting their complex ecology in Jordan. Further studies are needed to in‐depth investigate the diffusion of phytoplasma‐associated diseases of stone fruits throughout the Country, to clarify their aetiology, and to study their epidemiological pattern(s).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
‘Bois noir’ (BN) and flavescence dorèe (FD), the two main diseases of the grapevine yellows complex associated with genetically distinct phytoplasmas, have a complex epidemiology including multiple ...insect vectors and reservoir plants. This study investigated the presence of BN and FD phytoplasmas in nine groundcover plant species commonly utilized for inter-row vineyard green manure in Franciacorta (North Italy). The activities conducted in 2020 included monitoring and sampling groundcover plant species and symptomatic grapevines in September, and phytoplasma identification and typing by amplification and sequence analyses of
stamp
and
map
genes. Molecular analyses identified BN phytoplasma (strains carrying the
stamp
gene sequence variants St5, St19, St30) and FD phytoplasma (strains carrying the
map
gene sequence variant M54) in 72% and 28% of symptomatic grapevines, respectively. BN phytoplasma strains St5 and St30 were found also in
Eruca sativa
,
Vicia sativa
, and
Polygonum fagopyrum
. FD phytoplasma strain M54 was found also in
Vicia faba
,
Trifolium incarnatum
, and
Polygonum fagopyrum
. These results reinforced the evidence of the increasing range of BN and FD phytoplasma alternative plant hosts and suggested a criterium for the selection of the groundcover plant species utilized for green manure, excluding the ones putatively involved in BN and FD diffusion.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Epidemiological aspects and transmission routes of bois noir (BN), a grapevine yellows disease induced by ‘Candidatus Phytoplasma solani’, have been exhaustively studied in the affected vineyards of ...continental Europe but not in the Mediterranean coastal zone. Because ‘Ca. Phytoplasma solani’ and its principal vector Hyalesthes obsoletus presumably originate from the Mediterranean, gaining knowledge of the epidemiological peculiarities of the disease in this area is essential for understanding its global spread and diversification, as well as for designing local management strategies. In this study, molecular epidemiology was applied to trace transmission pathways of ‘Ca. Phytoplasma solani’ in the Mediterranean vineyards of Montenegro, using multilocus sequence typing of tuf, vmp1 and stamp genes of the isolates associated with various hosts. Thus, ‘Ca. Phytoplasma solani’ was tracked from a tentative reservoir plant (inoculum source) through an associated vector population to the infected grapevine. Three pathways of transmission were documented, originating from Urtica dioica, Convolvulus arvensis and Vitex agnus‐castus; however, only the route originating from U. dioica was direct, whereas the latter two were overlapping and could be intermixed. Vitex agnus‐castus is a natural source of ‘Ca. Phytoplasma solani’, representing an important link in disease epidemiology in the Mediterranean and a possible origin of several genotypes occurring in central Europe. Experimental confirmation of the role of Vitex‐associated H. obsoletus in BN transmission in Montenegrin vineyards indicates its tentative role as a vector in the wide area of the Mediterranean, where some of the major wine‐producing regions are located.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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