Publications by authors named "Antonio Valverde-Corredor"

14 Publications

  • Page 1 of 1

Evaluation of Indigenous Olive Biocontrol Rhizobacteria as Protectants against Drought and Salt Stress.

Microorganisms 2021 Jun 3;9(6). Epub 2021 Jun 3.

Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC), Avenida Menéndez Pidal s/n, Campus "Alameda del Obispo", 14004 Córdoba, Spain.

Stress caused by drought and salinity may compromise growth and productivity of olive ( L.) tree crops. Several studies have reported the use of beneficial rhizobacteria to alleviate symptoms produced by these stresses, which is attributed in some cases to the activity of 1-aminocyclopropane-1-carboxylic acid deaminase (ACD). A collection of beneficial olive rhizobacteria was in vitro screened for ACD activity. sp. PICF6 displayed this phenotype and sequencing of its genome confirmed the presence of an gene. In contrast, the well-known root endophyte and biocontrol agent PICF7 was defective in ACD activity, even though the presence of an ACD-coding gene was earlier predicted in its genome. In this study, an unidentified deaminase was confirmed instead. Greenhouse experiments with olive 'Picual' plants inoculated either with PICF6 or PICF7, or co-inoculated with both strains, and subjected to drought or salt stress were carried out. Several physiological and biochemical parameters increased in stressed plants (i.e., stomatal conductance and flavonoids content), regardless of whether or not they were previously bacterized. Results showed that neither PICF6 (ACD positive) nor PICF7 (ACD negative) lessened the negative effects caused by the abiotic stresses tested, at least under our experimental conditions.
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http://dx.doi.org/10.3390/microorganisms9061209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8230297PMC
June 2021

The Banana Root Endophytome: Differences between Mother Plants and Suckers and Evaluation of Selected Bacteria to Control f.sp. .

J Fungi (Basel) 2021 Mar 9;7(3). Epub 2021 Mar 9.

Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas (CSIC), Campus 'Alameda del Obispo' s/n, Avd. Menéndez Pidal s/n, 14004 Córdoba, Spain.

This study aimed to disentangle the structure, composition, and co-occurrence relationships of the banana (cv. Dwarf Cavendish) root endophytome comparing two phenological plant stages: mother plants and suckers. Moreover, a collection of culturable root endophytes (>1000) was also generated from Canary Islands. In vitro antagonism assays against f.sp. () races STR4 and TR4 enabled the identification and characterization of potential biocontrol agents (BCA). Eventually, three of them were selected and evaluated against Fusarium wilt of banana (FWB) together with the well-known BCA PICF7 under controlled conditions. Culturable and non-culturable (high-throughput sequencing) approaches provided concordant information and showed low microbial diversity within the banana root endosphere. appeared as the dominant genus and seemed to play an important role in the banana root endophytic microbiome according to co-occurrence networks. Fungal communities were dominated by the genera and . Overall, significant differences were found between mother plants and suckers, suggesting that the phenological stage determines the recruitment and organization of the endophytic microbiome. While selected native banana endophytes showed clear antagonism against strains, their biocontrol performance against FWB did not improve the outcome observed for a non-indigenous reference BCA (strain PICF7).
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http://dx.doi.org/10.3390/jof7030194DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8002102PMC
March 2021

Assessing the Involvement of Selected Phenotypes of PICF7 in Olive Root Colonization and Biological Control of .

Plants (Basel) 2021 Feb 23;10(2). Epub 2021 Feb 23.

Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC), Avenida Menéndez Pidal s/n, Campus "Alameda del Obispo", 14004 Córdoba, Spain.

PICF7 is an indigenous inhabitant of the olive ( L.) rhizosphere/root endosphere and an effective biocontrol agent against Verticillium wilt of olive (VWO), caused by the soil-borne fungus . This study aimed to evaluate the potential involvement of selected phenotypes of strain PICF7 in root colonization ability and VWO biocontrol. Therefore, a random transposon-insertion mutant bank of PICF7 was screened for the loss of phenotypes likely involved in rhizosphere/soil persistence (copper resistance), root colonization (biofilm formation) and plant growth promotion (phytase activity). Transposon insertions in genes putatively coding for the transcriptional regulator CusR or the chemotaxis protein CheV were found to affect copper resistance, whereas an insertion in gene putatively encoding a flagellar regulatory protein hampered the ability to form a biofilm. However, these mutants displayed the same antagonistic effect against as the parental strain. Remarkably, two mutants impaired in biofilm formation were never found inside olive roots, whereas their ability to colonize the root exterior and to control VWO remained unaffected. Endophytic colonization of olive roots was unaltered in mutants impaired in copper resistance and phytase production. Results demonstrated that the phenotypes studied were irrelevant for VWO biocontrol.
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http://dx.doi.org/10.3390/plants10020412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7926765PMC
February 2021

Comparative study of neighboring Holm oak and olive trees-belowground microbial communities subjected to different soil management.

PLoS One 2020 11;15(8):e0236796. Epub 2020 Aug 11.

Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain.

It is well-known that different plant species, and even plant varieties, promote different assemblages of the microbial communities associated with them. Here, we investigate how microbial communities (bacteria and fungi) undergo changes within the influence of woody plants (two olive cultivars, one tolerant and another susceptible to the soilborne fungal pathogen Verticillium dahliae, plus wild Holm oak) grown in the same soil but with different management (agricultural versus native). By the use of metabarcoding sequencing we determined that the native Holm oak trees rhizosphere bacterial communities were different from its bulk soil, with differences in some genera like Gp4, Gp6 and Solirubrobacter. Moreover, the agricultural management used in the olive orchard led to belowground microbiota differences with respect to the natural conditions both in bulk soils and rhizospheres. Indeed, Gemmatimonas and Fusarium were more abundant in olive orchard soils. However, agricultural management removed the differences in the microbial communities between the two olive cultivars, and these differences were minor respect to the olive bulk soil. According to our results, and at least under the agronomical conditions here examined, the composition and structure of the rhizospheric microbial communities do not seem to play a major role in olive tolerance to V. dahliae.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236796PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418964PMC
October 2020

Epigenetic Regulation of Virulence: Does DNA Methylation Level Play A Role?

Int J Mol Sci 2020 Jul 22;21(15). Epub 2020 Jul 22.

Center for Advanced Studies in Olive Grove and Olive Oils, Department of Experimental Biology, Univ. Jaén, 23071 Jaén, Spain.

is the etiological agent of Verticillium wilt of olive. The virulence of Defoliating isolates usually displays differences and high plasticity. This work studied whether an epigenetic mechanism was involved in this plasticity. An inverse correlation between virulence and DNA methylation of protein-coding genes was found. A set of 831 genes was selected for their highly consistent inverse methylation profile and virulence in the five studied isolates. Of these genes, ATP-synthesis was highly represented, which indicates that the more virulent D isolates are, the more energy requirements they may have. Furthermore, there were numerous genes in the protein biosynthesis process: genes coding for the chromatin structure, which suggests that epigenetic changes may also affect chromatin condensation; many transmembrane transporter genes, which is consistent with denser compounds, traffic through membranes in more virulent isolates; a fucose-specific lectin that may play a role in the attachment to plant cell walls during the host infection process; and pathogenic cutinases that facilitate plant invasion and sporulation genes for rapid spreading alongside plants. Our findings support the notion that differences in the virulence of the Defoliating isolates may be controlled, at least to some extent, by an epigenetic mechanism.
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http://dx.doi.org/10.3390/ijms21155197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7432615PMC
July 2020

Linking belowground microbial network changes to different tolerance level towards Verticillium wilt of olive.

Microbiome 2020 02 1;8(1):11. Epub 2020 Feb 1.

Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, CSIC, Campus 'Alameda del Obispo' s/n, Avd. Menéndez Pidal s/n, 14004, Córdoba, Spain.

Background: Verticillium wilt of olive (VWO) is caused by the soilborne fungal pathogen Verticillium dahliae. One of the best VWO management measures is the use of tolerant/resistant olive cultivars. Knowledge on the olive-associated microbiome and its potential relationship with tolerance to biotic constraints is almost null. The aims of this work are (1) to describe the structure, functionality, and co-occurrence interactions of the belowground (root endosphere and rhizosphere) microbial communities of two olive cultivars qualified as tolerant (Frantoio) and susceptible (Picual) to VWO, and (2) to assess whether these communities contribute to their differential disease susceptibility level.

Results: Minor differences in alpha and beta diversities of root-associated microbiota were detected between olive cultivars regardless of whether they were inoculated or not with the defoliating pathotype of V. dahliae. Nevertheless, significant differences were found in taxonomic composition of non-inoculated plants' communities, "Frantoio" showing a higher abundance of beneficial genera in contrast to "Picual" that exhibited major abundance of potential deleterious genera. Upon inoculation with V. dahliae, significant changes at taxonomic level were found mostly in Picual plants. Relevant topological alterations were observed in microbial communities' co-occurrence interactions after inoculation, both at structural and functional level, and in the positive/negative edges ratio. In the root endosphere, Frantoio communities switched to highly connected and low modularized networks, while Picual communities showed a sharply different behavior. In the rhizosphere, V. dahliae only irrupted in the microbial networks of Picual plants.

Conclusions: The belowground microbial communities of the two olive cultivars are very similar and pathogen introduction did not provoke significant alterations in their structure and functionality. However, notable differences were found in their networks in response to the inoculation. This phenomenon was more evident in the root endosphere communities. Thus, a correlation between modifications in the microbial networks of this microhabitat and susceptibility/tolerance to a soilborne pathogen was found. Moreover, V. dahliae irruption in the Picual microbial networks suggests a stronger impact on the belowground microbial communities of this cultivar upon inoculation. Our results suggest that changes in the co-occurrence interactions may explain, at least partially, the differential VWO susceptibility of the tested olive cultivars. Video abstract.
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http://dx.doi.org/10.1186/s40168-020-0787-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6995654PMC
February 2020

Defining the root endosphere and rhizosphere microbiomes from the World Olive Germplasm Collection.

Sci Rep 2019 12 31;9(1):20423. Epub 2019 Dec 31.

Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Calle Profesor Albareda 1, 18008, Granada, Spain.

The bacterial and fungal communities from the olive (Olea europaea L.) root systems have not yet been simultaneously studied. We show in this work that microbial communities from the olive root endosphere are less diverse than those from the rhizosphere. But more relevant was to unveil that olive belowground communities are mainly shaped by the genotype of the cultivar when growing under the same environmental, pedological and agronomic conditions. Furthermore, Actinophytocola, Streptomyces and Pseudonocardia are the most abundant bacterial genera in the olive root endosphere, Actinophytocola being the most prevalent genus by far. In contrast, Gp6, Gp4, Rhizobium and Sphingomonas are the main genera in the olive rhizosphere. Canalisporium, Aspergillus, Minimelanolocus and Macrophomina are the main fungal genera present in the olive root system. Interestingly enough, a large number of as yet unclassified fungal sequences (class level) were detected in the rhizosphere. From the belowground microbial profiles here reported, it can be concluded that the genus Actinophytocola may play an important role in olive adaptation to environmental stresses. Moreover, the huge unknown fungal diversity here uncovered suggests that fungi with important ecological function and biotechnological potential are yet to be identified.
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http://dx.doi.org/10.1038/s41598-019-56977-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6938483PMC
December 2019

Indigenous spp. Strains from the Olive ( L.) Rhizosphere as Effective Biocontrol Agents against : From the Host Roots to the Bacterial Genomes.

Front Microbiol 2018 23;9:277. Epub 2018 Feb 23.

Department of Crop Protection, Institute for Sustainable Agriculture (CSIC), Córdoba, Spain.

The use of biological control agents (BCA), alone or in combination with other management measures, has gained attention over the past decades, driven by the need to seek for sustainable and eco-friendly alternatives to confront plant pathogens. The rhizosphere of olive ( L.) plants is a source of bacteria with potential as biocontrol tools against Verticillium wilt of olive (VWO) caused by Kleb. A collection of bacterial isolates from healthy nursery-produced olive (cultivar Picual, susceptible to VWO) plants was generated based on morphological, biochemical and metabolic characteristics, chemical sensitivities, and on their antagonistic activity against several olive pathogens. Three strains (PIC25, PIC105, and PICF141) showing high inhibition ability of pathogens' growth, particularly against , were eventually selected. Their effectiveness against VWO caused by the defoliating pathotype of was also demonstrated, strain PICF141 being the rhizobacteria showing the best performance as BCA. Genotypic and phenotypic traits traditionally associated with plant growth promotion and/or biocontrol abilities were evaluated as well (e.g., phytase, xylanase, catalase, cellulase, chitinase, glucanase activities, and siderophore and HCN production). Multi-locus sequence analyses of conserved genes enabled the identification of these strains as spp. Strain PICF141 was affiliated to the " subgroup," within the " group," being the closest species. Strains PIC25 and PIC105 were affiliated to the " group," being the closest relative. Moreover, we identified (PIC105) for the first time as a BCA. Genome sequencing and analyses allowed the identification of traits commonly associated with plant-bacteria interactions. Finally, the root colonization ability of these olive rhizobacteria was assessed, providing valuable information for the future development of formulations based on these strains. A set of actions, from rhizosphere isolation to genome analysis, is proposed and discussed for selecting indigenous rhizobacteria as effective BCAs.
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http://dx.doi.org/10.3389/fmicb.2018.00277DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5829093PMC
February 2018

Tolerance of olive (Olea europaea) cv Frantoio to Verticillium dahliae relies on both basal and pathogen-induced differential transcriptomic responses.

New Phytol 2018 01 12;217(2):671-686. Epub 2017 Oct 12.

Department of Crop Protection, Institute for Sustainable Agriculture, Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC), Campus 'Alameda del Obispo', Avenida Menéndez Pidal s/n, Apartado, Córdoba, 14004, Spain.

Verticillium wilt of olive (VWO) is one of the most serious biotic constraints for this tree crop. Our knowledge of the genetics of the tolerance/resistance to this disease is very limited. Here we show that tolerance of the cv Frantoio relies on both basal and early pathogen-induced differential transcriptomic responses. A comparative transcriptomic analysis (RNA-seq) was conducted in root tissues of cvs Frantoio (VWO-tolerant) and Picual (VWO-susceptible). RNA samples originated from roots of inoculated olive plants during the early infection stages by Verticillium dahliae (highly virulent, defoliating pathotype). A huge number of differentially expressed genes (DEGs) were found between 'Frantoio' and 'Picual' (27 312 unigenes) in the absence of the pathogen. Upon infection with V. dahliae, 'Picual' and 'Frantoio' plants responded differently too. In the early infection stages, four clusters of DEGs could be identified according to their time-course expression patterns. Among others, a pathogenesis-related protein of the Bet v I family and a dirigent-like protein involved in lignification, and several BAK1, NHL1, reactive oxygen species stress response and BAM unigenes showed noticeable differences between cultivars. Tolerance of 'Frantoio' plants to VWO is a consequence of a complex and multifaceted process which involves many plant traits.
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http://dx.doi.org/10.1111/nph.14833DOI Listing
January 2018

Systemic responses in a tolerant olive (Olea europaea L.) cultivar upon root colonization by the vascular pathogen Verticillium dahliae.

Front Microbiol 2015 16;6:928. Epub 2015 Sep 16.

Department of Crop Protection, Institute for Sustainable Agriculture, Consejo Superior de Investigaciones Científicas Córdoba, Spain.

Verticillium wilt of olive (VWO) is caused by the vascular pathogen Verticillium dahliae. One of the best VWO management measures is the use of tolerant cultivars; however, our knowledge on VWO tolerance/resistance genetics is very limited. A transcriptomic analysis was conducted to (i) identify systemic defense responses induced/repressed in aerial tissues of the tolerant cultivar Frantoio upon root colonization by V. dahliae, and (ii) determine the expression pattern of selected defense genes in olive cultivars showing differential susceptibility to VWO. Two suppression subtractive hybridization cDNA libraries, enriched in up-regulated (FU) and down-regulated (FD) genes respectively, were generated from "Frantoio" aerial tissues. Results showed that broad systemic transcriptomic changes are taking place during V. dahliae-"Frantoio" interaction. A total of 585 FU and 381 FD unigenes were identified, many of them involved in defense response to (a)biotic stresses. Selected genes were then used to validate libraries and evaluate their temporal expression pattern in "Frantoio." Four defense genes were analyzed in cultivars Changlot Real (tolerant) and Picual (susceptible). An association between GRAS1 and DRR2 gene expression patterns and susceptibility to VWO was observed, suggesting that these transcripts could be further evaluated as markers of the tolerance level of olive cultivars to V. dahliae.
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http://dx.doi.org/10.3389/fmicb.2015.00928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4584997PMC
October 2015

Early and delayed long-term transcriptional changes and short-term transient responses during cold acclimation in olive leaves.

DNA Res 2015 Feb 16;22(1):1-11. Epub 2014 Oct 16.

Departamento de Biología Experimental, Universidad de Jaén, Jaén, Spain

Low temperature severely affects plant growth and development. To overcome this constraint, several plant species from regions having a cool season have evolved an adaptive response, called cold acclimation. We have studied this response in olive tree (Olea europaea L.) cv. Picual. Biochemical stress markers and cold-stress symptoms were detected after the first 24 h as sagging leaves. After 5 days, the plants were found to have completely recovered. Control and cold-stressed plants were sequenced by Illumina HiSeq 1000 paired-end technique. We also assembled a new olive transcriptome comprising 157,799 unigenes and found 6,309 unigenes differentially expressed in response to cold. Three types of response that led to cold acclimation were found: short-term transient response, early long-term response, and late long-term response. These subsets of unigenes were related to different biological processes. Early responses involved many cold-stress-responsive genes coding for, among many other things, C-repeat binding factor transcription factors, fatty acid desaturases, wax synthesis, and oligosaccharide metabolism. After long-term exposure to cold, a large proportion of gene down-regulation was found, including photosynthesis and plant growth genes. Up-regulated genes after long-term cold exposure were related to organelle fusion, nucleus organization, and DNA integration, including retrotransposons.
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http://dx.doi.org/10.1093/dnares/dsu033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4379972PMC
February 2015

The biocontrol endophytic bacterium Pseudomonas fluorescens PICF7 induces systemic defense responses in aerial tissues upon colonization of olive roots.

Front Microbiol 2014 5;5:427. Epub 2014 Sep 5.

Lab Plant-Microbe Interactions, Department of Crop Protection, Institute for Sustainable Agriculture, Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC) Córdoba, Spain.

Pseudomonas fluorescens PICF7, a native olive root endophyte and effective biocontrol agent (BCA) against Verticillium wilt of olive, is able to trigger a broad range of defense responses in root tissues of this woody plant. In order to elucidate whether strain PICF7 also induces systemic defense responses in above-ground organs, aerial tissues of olive plants grown under non-gnotobiotic conditions were collected at different time points after root bacterization with this endophytic BCA. A suppression subtractive hybridization (SSH) cDNA library, enriched in up-regulated genes, was generated. This strategy enabled the identification of 376 ESTs (99 contigs and 277 singlets), many of them related to response to different stresses. Five ESTs, involved in defense responses, were selected to carry out time-course quantitative real-time PCR (qRT-PCR) experiments aiming to: (1) validate the induction of these genes, and (2) shed light on their expression pattern along time (from 1 to 15 days). Induction of olive genes potentially coding for lipoxygenase 2, catalase, 1-aminocyclopropane-1-carboxylate oxidase, and phenylananine ammonia-lyase was thus confirmed at some time points. Computational analysis also revealed that different transcription factors were up-regulated in olive aerial tissues (i.e., JERF, bHLH, WRKY), as previously reported for roots. Results confirmed that root colonization by this endophytic bacterium does not only trigger defense responses in this organ but also mounts a wide array of systemic defense responses in distant tissues (stems, leaves). This sheds light on how olive plants respond to the "non-hostile" colonization by a bacterial endophyte and how induced defense response can contribute to the biocontrol activity of strain PICF7.
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http://dx.doi.org/10.3389/fmicb.2014.00427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4155815PMC
September 2014

Colonization process of olive tissues by Verticillium dahliae and its in planta interaction with the biocontrol root endophyte Pseudomonas fluorescens PICF7.

Microb Biotechnol 2009 Jul 9;2(4):499-511. Epub 2009 Apr 9.

Departamento de Mejora Genética, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas, Alameda del Obispo s/n, Apartado 4084, 14080 Córdoba, Spain.

The colonization process of Olea europaea by the defoliating pathotype of Verticillium dahliae, and the in planta interaction with the endophytic, biocontrol strain Pseudomonas fluorescens PICF7 were determined. Differential fluorescent protein tagging was used for the simultaneous visualization of P. fluorescens PICF7 and V. dahliae in olive tissues. Olive plants were bacterized with PICF7 and then transferred to V. dahliae-infested soil. Monitoring olive colonization events by V. dahliae and its interaction with PICF7 was conducted using a non-gnotobiotic system, confocal laser scanner microscopy and tissue vibratoming sections. A yellow fluorescently tagged V. dahliae derivative (VDAT-36I) was obtained by Agrobacterium tumefaciens-mediated transformation. Isolate VDAT-36I quickly colonized olive root surface, successfully invaded root cortex and vascular tissues via macro- and micro-breakages, and progressed to the aerial parts of the plant through xylem vessel cells. Strain PICF7 used root hairs as preferred penetration site, and once established on/in root tissues, hindered pathogen colonization. For the first time using this approach, the entire colonization process of a woody plant by V. dahliae is reported. Early and localized root surface and root endophytic colonization by P. fluorescens PICF7 is needed to impair full progress of verticillium wilt epidemics in olive.
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http://dx.doi.org/10.1111/j.1751-7915.2009.00105.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3815910PMC
July 2009

Molecular Variability Within and Among Verticillium dahliae Vegetative Compatibility Groups Determined by Fluorescent Amplified Fragment Length Polymorphism and Polymerase Chain Reaction Markers.

Phytopathology 2006 May;96(5):485-95

ABSTRACT A degree of genetic diversity may exist among Verticillium dahliae isolates within vegetative compatibility groups (VCGs) that bears phytopathological significance and is worth investigating using molecular tools of a higher resolution than VCG characterization. The molecular variability within and among V. dahliae VCGs was studied using 53 artichoke isolates from eastern-central Spain, 96 isolates from cotton, 7 from cotton soil, and 45 from olive trees in countries of the Mediterranean Basin. Isolates were selected to represent the widest available diversity in cotton- and olive-defoliating (D) and -nondefoliating (ND) pathotypes, as well as for VCG. The VCG of 96 cotton and olive isolates was determined in this present study. Molecular variability among V. dahliae isolates was assessed by fluorescent amplified fragment length polymorphism (AFLP) analysis and by polymerase chain reaction (PCR) assays for DNA fragments associated with the D (462 bp) and ND (824 bp) pathotypes, as well as a 334-bp amplicon associated with D pathotype isolates but also present in some VCG2B isolates. Isolates from cotton were in VCG1A, VCG1B, VCG2A, VCG2B, and VCG4B and those from olive trees were in VCG1A, VCG2A, and VCG4B. Artichoke isolates included representatives of VCG1A, VCG2A, VCG2B (including a newly identified VCG2Ba), and VCG4B. AFLP data were used to generate matrixes of genetic distance among isolates for cluster analysis using the neighbor-joining method and for analysis of molecular variance. Results demonstrated that V. dahliae isolates within a VCG subgroup are molecularly similar, to the extent that clustering of isolates correlated with VCG subgroups regardless of the host source and geographic origin. VCGs differed in molecular variability, with the variability being highest in VCG2B and VCG2A. For some AFLP/VCG subgroup clusterings, V. dahliae isolates from artichoke grouped in subclusters clearly distinct from those comprising isolates from cotton and olive trees. In addition, VCG2B isolates from artichoke formed two distinct clusters that correlated with PCR markers of 334 bp (VCG2B(334)) or 824 bp (VCG2B(824)). Artichoke isolates in the VCG2B(334)/2beta(334) cluster were molecularly similar to isolates of VCG1A. The molecular difference found among artichoke isolates in VCG2B correlates with virulence of isolates to artichoke and cotton cultivars demonstrated in a previous study.
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http://dx.doi.org/10.1094/PHYTO-96-0485DOI Listing
May 2006
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