RESUMO
BACKGROUND: Xylella fastidiosa is a multi-host bacterium that can be detected in hundreds of plant species including several crops. Diseases caused by X. fastidiosa are considered a threat to global food production. The primary method for managing diseases caused by X. fastidiosa involves using insecticides to control the vector. Hence, it is necessary to adopt new and sustainable disease management technologies to control not only the insect but also the bacteria and plant health. We demonstrated that N-acetylcysteine (NAC), a low-cost cysteine analogue, is a sustainable molecule that can be used in agriculture to decrease the damage caused by X. fastidiosa and improve plant health. RESULTS: Using 15N-NAC we proved that this analogue was absorbed by the roots and transported to different parts of the plant. Inside the plant, NAC reduced the bacterial population by 60-fold and the number of xylem vessels blocked by bacterial biofilms. This reflected in a recovery of 0.28-fold of the daily sap flow compared to health plants. In addition, NAC-treated citrus variegated chlorosis (CVC) plants decreased the oxidative stress by improving the activity of detoxifying enzymes. Moreover, the use of NAC in field conditions positively contributed to the increase in fruit yield of CVC-diseased plants. CONCLUSION: Our research not only advances the understanding of NAC absorption in plants, but also indicates its dual effect as an antimicrobial and antioxidant molecule. This, in turn, negatively affects bacterial survival while improving plant health by decreasing oxidative stress. Overall, the positive field-based evidence supports the viability of NAC as a sustainable agricultural application. © 2024 Society of Chemical Industry.
Assuntos
Acetilcisteína , Doenças das Plantas , Xylella , Xylella/efeitos dos fármacos , Xylella/fisiologia , Acetilcisteína/farmacologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Citrus/microbiologia , Frutas/microbiologiaRESUMO
While there are documented host shifts in many bacterial plant pathogens, the genetic foundation of host shifts is largely unknown. Xylella fastidiosa is a bacterial pathogen found in over 600 host plant species. Two parallel host shifts occurred-in Brazil and Italy-in which X. fastidiosa adapted to infect olive trees, whereas related strains infected coffee. Using 10 novel whole-genome sequences from an olive-infecting population in Brazil, we investigated whether these olive-infecting strains diverged from closely related coffee-infecting strains. Several single-nucleotide polymorphisms, many derived from recombination events, and gene gain and loss events separated olive-infecting strains from coffee-infecting strains in this clade. The olive-specific variation suggests that this event was a host jump with genetic isolation between coffee- and olive-infecting X. fastidiosa populations. Next, we investigated the hypothesis of genetic convergence in the host shift from coffee to olive in both populations (Brazil and Italy). Each clade had multiple mutations and gene gain and loss events unique to olive, yet no overlap between clades. Using a genome-wide association study technique, we did not find any plausible candidates for convergence. Overall, this work suggests that the two populations adapted to infect olive trees through independent genetic solutions.
Assuntos
Café , Xylella , Café/microbiologia , Estudo de Associação Genômica Ampla , Xylella/genética , Brasil , Doenças das Plantas/microbiologiaRESUMO
BACKGROUND: Pathogens with a global distribution face diverse biotic and abiotic conditions across populations. Moreover, the ecological and evolutionary history of each population is unique. Xylella fastidiosa is a xylem-dwelling bacterium infecting multiple plant hosts, often with detrimental effects. As a group, X. fastidiosa is divided into distinct subspecies with allopatric historical distributions and patterns of multiple introductions from numerous source populations. The capacity of X. fastidiosa to successfully colonize and cause disease in naïve plant hosts varies among subspecies, and potentially, among populations. Within Central America (i.e. Costa Rica) two X. fastidiosa subspecies coexist: the native subsp. fastidiosa and the introduced subsp. pauca. Using whole genome sequences, the patterns of gene gain/loss, genomic introgression, and genetic diversity were characterized within Costa Rica and contrasted to other X. fastidiosa populations. RESULTS: Within Costa Rica, accessory and core genome analyses showed a highly malleable genome with numerous intra- and inter-subspecific gain/loss events. Likewise, variable levels of inter-subspecific introgression were found within and between both coexisting subspecies; nonetheless, the direction of donor/recipient subspecies to the recombinant segments varied. Some strains appeared to recombine more frequently than others; however, no group of genes or gene functions were overrepresented within recombinant segments. Finally, the patterns of genetic diversity of subsp. fastidiosa in Costa Rica were consistent with those of other native populations (i.e. subsp. pauca in Brazil). CONCLUSIONS: Overall, this study shows the importance of characterizing local evolutionary and ecological history in the context of world-wide pathogen distribution.
Assuntos
Evolução Molecular , Xylella/genética , Costa Rica , Introgressão Genética , Variação Genética , Genoma Bacteriano/genética , Espécies Introduzidas , Filogenia , Filogeografia , Doenças das Plantas/microbiologia , Recombinação Genética , Especificidade da Espécie , Xylella/classificação , Xylella/isolamento & purificaçãoRESUMO
Pathogen introductions have led to numerous disease outbreaks in naive regions of the globe. The plant pathogen Xylella fastidiosa has been associated with various recent epidemics in Europe affecting agricultural crops, such as almond, grapevine, and olive, but also endemic species occurring in natural forest landscapes and ornamental plants. We compared whole-genome sequences of X. fastidiosa subspecies multiplex from America and strains associated with recent outbreaks in southern Europe to infer their likely origins and paths of introduction within and between the two continents. Phylogenetic analyses indicated multiple introductions of X. fastidiosa subspecies multiplex into Italy, Spain, and France, most of which emerged from a clade with limited genetic diversity with a likely origin in California, USA. The limited genetic diversity observed in X. fastidiosa subspecies multiplex strains originating from California is likely due to the clade itself being an introduction from X. fastidiosa subspecies multiplex populations in the southeastern United States, where this subspecies is most likely endemic. Despite the genetic diversity found in some areas in Europe, there was no clear evidence of recombination occurring among introduced X. fastidiosa strains in Europe. Sequence type taxonomy, based on multilocus sequence typing (MLST), was shown, at least in one case, to not lead to monophyletic clades of this pathogen; whole-genome sequence data were more informative in resolving the history of introductions than MLST data. Although additional data are necessary to carefully tease out the paths of these recent dispersal events, our results indicate that whole-genome sequence data should be considered when developing management strategies for X. fastidiosa outbreaks.IMPORTANCEXylella fastidiosa is an economically important plant-pathogenic bacterium that has emerged as a pathogen of global importance associated with a devastating epidemic in olive trees in Italy associated with X. fastidiosa subspecies pauca and other outbreaks in Europe, such as X. fastidiosa subspecies fastidiosa and X. fastidiosa subspecies multiplex in Spain and X. fastidiosa subspecies multiplex in France. We present evidence of multiple introductions of X. fastidiosa subspecies multiplex, likely from the United States, into Spain, Italy, and France. These introductions illustrate the risks associated with the commercial trade of plant material at global scales and the need to develop effective policy to limit the likelihood of pathogen pollution into naive regions. Our study demonstrates the need to utilize whole-genome sequence data to study X. fastidiosa introductions at outbreak stages, since a limited number of genetic markers does not provide sufficient phylogenetic resolution to determine dispersal paths or relationships among strains that are of biological and quarantine relevance.
Assuntos
Genoma Bacteriano , Doenças das Plantas/microbiologia , Xylella/genética , Brasil , Europa (Continente) , Espécies Introduzidas , Sequenciamento Completo do GenomaRESUMO
The Asian citrus psyllid (ACP) Diaphorina citri, vector of 'Candidatus Liberibacter asiaticus' (CLas), the putative causal agent of citrus Huanglongbing (HLB), is controlled by application of insecticides, which, although effective, has resulted in serious biological imbalances. New management tools are needed, and the technique known as "trap crop" has been attracting attention. A potential plant for use as a trap crop in the management of the ACP is Murraya koenigii (curry leaf). However, for this plant to be used in the field, it needs to be attractive for the vector and must not harbor CLas. To verify the potential of curry leaf as trap crop for the management of HLB, we investigated the ability of D. citri to transmit CLas to M. koenigii, and to other test plants, including M. paniculata (orange jasmine) and cultivar Valencia sweet-orange seedlings. For the tests, the insects were reared on a symptomatic CLas-infected plant and allowed to feed on the three test plant species. The overall maximum transmission rate for the citrus seedlings was 83.3%, and for orange jasmine was 33.3%. Successful transmission of CLas by ACP to the curry-leaf seedlings was not observed, and it was treated as immune to CLas. Supported by the previous results that M. koenigii is attractive for ACP, these results indicate that curry leaf is an excellent candidate for use as a trap crop, to improve the management of the insect vector and consequently of HLB.
Assuntos
Citrus sinensis/imunologia , Citrus/imunologia , Hemípteros/microbiologia , Murraya/imunologia , Doenças das Plantas/prevenção & controle , Rhizobiaceae/patogenicidade , Animais , Citrus/microbiologia , Citrus sinensis/microbiologia , Insetos Vetores/microbiologia , Murraya/microbiologia , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Plântula/imunologia , Plântula/microbiologiaRESUMO
Citrus sudden death (CSD) has caused the death of approximately four million orange trees in a very important citrus region in Brazil. Although its etiology is still not completely clear, symptoms and distribution of affected plants indicate a viral disease. In a search for viruses associated with CSD, we have performed a comparative high-throughput sequencing analysis of the transcriptome and small RNAs from CSD-symptomatic and -asymptomatic plants using the Illumina platform. The data revealed mixed infections that included Citrus tristeza virus (CTV) as the most predominant virus, followed by the Citrus sudden death-associated virus (CSDaV), Citrus endogenous pararetrovirus (CitPRV) and two putative novel viruses tentatively named Citrus jingmen-like virus (CJLV), and Citrus virga-like virus (CVLV). The deep sequencing analyses were sensitive enough to differentiate two genotypes of both viruses previously associated with CSD-affected plants: CTV and CSDaV. Our data also showed a putative association of the CSD-symptomatic plants with a specific CSDaV genotype and a likely association with CitPRV as well, whereas the two putative novel viruses showed to be more associated with CSD-asymptomatic plants. This is the first high-throughput sequencing-based study of the viral sequences present in CSD-affected citrus plants, and generated valuable information for further CSD studies.
Assuntos
Citrus/virologia , Coinfecção/virologia , Doenças das Plantas/virologia , Vírus de Plantas/genética , Vírus de Plantas/isolamento & purificação , RNA de Plantas/química , RNA de Plantas/genética , Brasil , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala , Vírus de Plantas/classificação , Pequeno RNA não Traduzido/química , Pequeno RNA não Traduzido/genética , RNA Viral/química , RNA Viral/genéticaRESUMO
Xylella fastidiosa, an economically important plant-pathogenic bacterium, infects both coffee and citrus trees in Brazil. Although X. fastidiosa in citrus is well studied, knowledge about the population structure of this bacterium infecting coffee remains unknown. Here, we studied the population structure of X. fastidiosa infecting coffee trees in São Paulo State, Brazil, in four regions where citrus is also widely cultivated. Genotyping of over 500 isolates from coffee plants using 14 genomic microsatellite markers indicated that populations were largely geographically isolated, as previously found with populations of X. fastidiosa infecting citrus. These results were supported by a clustering analysis, which indicated three major genetic groups among the four sampled regions. Overall, approximately 38% of isolates showed significant membership coefficients not related to their original geographical populations (i.e., migrants), characterizing a significant degree of genotype flow among populations. To determine whether admixture occurred between isolates infecting citrus and coffee plants, one site with citrus and coffee orchards adjacent to each other was selected; over 100 isolates were typed from each host plant. No signal of natural admixture between citrus- and coffee-infecting isolates was found; artificial cross-infection assays with representative isolates also yielded no successful cross infection. A comparison determined that X. fastidiosa populations from coffee have higher genetic diversity and allelic richness compared with citrus. The results showed that coffee and citrus X. fastidiosa populations are effectively isolated from each other and, although coffee populations are spatially structured, migration has an important role in shaping diversity.
Assuntos
Citrus/microbiologia , Coffea/microbiologia , Variação Genética , Doenças das Plantas/microbiologia , Xylella/genética , Alelos , Brasil , Genômica , Genótipo , Repetições de Microssatélites/genética , Análise Espacial , Simpatria , Xylella/isolamento & purificaçãoRESUMO
Homologous recombination affects the evolution of bacteria such as Xylella fastidiosa, a naturally competent plant pathogen that requires insect vectors for dispersal. This bacterial species is taxonomically divided into subspecies, with phylogenetic clusters within subspecies that are host specific. One subspecies, pauca, is primarily limited to South America, with the exception of recently reported strains in Europe and Costa Rica. Despite the economic importance of X. fastidiosa subsp. pauca in South America, little is known about its genetic diversity. Multilocus sequence typing (MLST) has previously identified six sequence types (ST) among plant samples collected in Brazil (both subsp. pauca and multiplex). Here, we report on a survey of X. fastidiosa genetic diversity (MLST based) performed in six regions in Brazil and two in Argentina, by sampling five different plant species. In addition to the six previously reported ST, seven new subsp. pauca and two new subsp. multiplex ST were identified. The presence of subsp. multiplex in South America is considered to be the consequence of a single introduction from its native range in North America more than 80 years ago. Different phylogenetic approaches clustered the South American ST into four groups, with strains infecting citrus (subsp. pauca); coffee and olive (subsp. pauca); coffee, hibiscus, and plum (subsp. pauca); and plum (subsp. multiplex). In areas where these different genetic clusters occurred sympatrically, we found evidence of homologous recombination in the form of bidirectional allelic exchange between subspp. pauca and multiplex. In fact, the only strain of subsp. pauca isolated from a plum host had an allele that originated from subsp. multiplex. These signatures of bidirectional homologous recombination between endemic and introduced ST indicate that gene flow occurs in short evolutionary time frames in X. fastidiosa, despite the ecological isolation (i.e., host plant species) of genotypes.
Assuntos
Citrus/microbiologia , Variação Genética , Recombinação Homóloga , Doenças das Plantas/microbiologia , Xylella/genética , Alelos , Genótipo , Geografia , Família Multigênica , Tipagem de Sequências Multilocus , Filogenia , Análise de Sequência de DNA , América do Sul , Xylella/isolamento & purificação , Xylella/patogenicidadeRESUMO
Strains of Xylella fastidiosa constitute a complex group of bacteria that develop within the xylem of many plant hosts, causing diseases of significant economic importance, such as Pierce's disease in North American grapevines and citrus variegated chlorosis in Brazil. X. fastidiosa has also been obtained from other host plants, in direct correlation with the development of diseases, as in the case of coffee leaf scorch (CLS)--a disease with potential to cause severe economic losses to the Brazilian coffee industry. This paper describes a thorough genomic characterization of coffee-infecting X. fastidiosa strains, initially performed through a microarray-based approach, which demonstrated that CLS strains could be subdivided in two phylogenetically distinct subgroups. Whole-genomic sequencing of two of these bacteria (one from each subgroup) allowed identification of ORFs and horizontally transferred elements (HTEs) that were specific to CLS-related X. fastidiosa strains. Such analyses confirmed the size and importance of HTEs as major mediators of chromosomal evolution amongst these bacteria, and allowed identification of differences in gene content, after comparisons were made with previously sequenced X. fastidiosa strains, isolated from alternative hosts. Although direct experimentation still needs to be performed to elucidate the biological consequences associated with such differences, it was interesting to verify that CLS-related bacteria display variations in genes that produce toxins, as well as surface-related factors (such as fimbrial adhesins and LPS) that have been shown to be involved with recognition of specific host factors in different pathogenic bacteria.
Assuntos
Coffea/microbiologia , Genoma Bacteriano , Genômica , Xylella/genética , Brasil , Cromossomos Bacterianos , Hibridização Genômica Comparativa , Biologia Computacional , Elementos de DNA Transponíveis , Evolução Molecular , Fases de Leitura Aberta , Filogenia , Doenças das Plantas/microbiologia , Xylella/classificação , Xylella/isolamento & purificaçãoRESUMO
The ecology of plant pathogens of perennial crops is affected by the long-lived nature of their immobile hosts. In addition, changes to the genetic structure of pathogen populations may affect disease epidemiology and management practices; examples include local adaptation of more fit genotypes or introduction of novel genotypes from geographically distant areas via human movement of infected plant material or insect vectors. We studied the genetic structure of Xylella fastidiosa populations causing disease in sweet orange plants in Brazil at multiple scales using fast-evolving molecular markers (simple-sequence DNA repeats). Results show that populations of X. fastidiosa were regionally isolated, and that isolation was maintained for populations analyzed a decade apart from each other. However, despite such geographic isolation, local populations present in year 2000 were largely replaced by novel genotypes in 2009 but not as a result of migration. At a smaller spatial scale (individual trees), results suggest that isolates within plants originated from a shared common ancestor. In summary, new insights on the ecology of this economically important plant pathogen were obtained by sampling populations at different spatial scales and two different time points.