Publications by authors named "Blanca B Landa"

52 Publications

First report of Verticillium wilt caused by Verticillium dahliae on Russian olive (Elaeagnus angustifolia) in Iran.

Plant Dis 2020 Dec 9. Epub 2020 Dec 9.

Agricultural and Natural Resources Research Center of Semnan Province (Shahrood), AREEO, Shahrood, Iran. , Plant Protection Research Departmet, Agricultural and Natural Resources Research Center of Semnan Province (Shahrood), Bastam, Shahrood, Iran, Shahrood, Shahrood/Semnan, Iran (the Islamic Republic of), 3641614811;

Russian olive, also known as, Persian olive or oleaster (Elaeagnus angustifolia L.) is a species in the Elaeagnaceae family native to western and central Asia. In some orchards in Iran, intercropping Russian olive or Prunus trees with vegetables is a common practice. In 2018, about 130 ha of E. angustifolia orchards in Shahrood, Semnan Province, Iran showed branch wilting and dieback. Symptoms on affected trees started with yellowing of the lower leaves, followed by wilting and finally death of affected branches. Sections of stems indicated brown or black streaks in the vascular tissues under the bark. Isolations were made from discolored vascular tissues by surface-disinfesting small pieces of tissue with 0.5% sodium hypochlorite for 2 min, plating them onto potato dextrose agar amended with 25 mg/l streptomycin sulfate and incubated in the dark for 14 days at 25°C. Fungi consistently isolated from symptomatic tissues. Fungal isolates were identified as Verticillium dahliae Kleb. based on characteristics of verticillate conidiophores, hyaline, elliptical, single celled conidia measuring 4.7-6.0 × 2.3-3.4 μm (n = 100) and irregular, dark microsclerotia measuring 27-34 × 22-26 μm (n = 50) that developed after 14 days of growth at 25°C in the dark. The identification of two isolates was further confirmed by performing real-time PCR assay using a pair of specific primers for internal transcribed spacer (ITS) region of V. dahliae as previously described (Hiemstra et al. 2013). In addition, the molecular subdivision of isolates was further determined to discriminate D and ND molecular types (Keykhasaber 2017). According to molecular assays, isolates were identified as V. dahliae and grouped with ND types. The pathogenicity of isolates was evaluated by root-dipping one-year E. angustifolia seedlings (10 seedlings) into conidial suspensions of 1×107 cfu/ml. Inoculated plants were transplanted in pots containing autoclaved soil and maintained in a greenhouse at 25°C until symptoms appearance. Two seedlings were treated with sterile distilled water as controls. All inoculated seedlings started to show wilting symptoms similar to those present in naturally affected trees within 30 days after inoculation and died thereafter. Furthermore, V. dahliae was consistently isolated from symptomatic tissues. No symptoms were observed on the control plants. The pathogenicity test was repeated twice with similar results. To the best of our knowledge, this is the first report of Verticillium wilt on Russian olive trees in Iran. In Iran, Verticillium wilt is the cause of serious losses in many woody and herbaceous plants with economic importance including many trees belonging to the genus Prunus that are highly susceptible to the disease. In Shahrood (Semnan Province), most agricultural fields have a potato- or tomato- growing history. Verticillium wilt may become an important economic problem in many Russian olive and Prunus orchards in the future since their cultivation is expanding rapidly in many agricultural areas previously dedicated to tomato and potato crops, the majority of which are infested with V. dahliae. References Hiemstra, J. A., Korthals, G. W., Visser, J. H. M., Dalfsen, P. v., Sluis, B. J. v. d., and Smits, A. P. 2013. Control of Verticillium in tree nurseries through biological soil disinfestation. Pages 62-62 in: 11th International Verticillium Symposium, Georg-August-Universität,Göttingen, Germany, 5-8 May 2013, B. Koopmann and A. von Tiedemann, eds. DPG Spectrum Phytomedizin, Göttingen. Keykhasaber, M., Faino L., van den Berg, G.C.M., Hiemstra, J. A., Thomma, B. P. H. J. 2017. A robust method for discriminating defoliating and the non-defoliating pathotypes of V. dahliae. . In; Keykhasaber M. thesis 62-84. Sun, M., and Lin, Q. 2010. A revision of Elaeagnus L. (Elaeagnaceae) in mainland China. J. Systematics and Evolution 48:356-390.
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http://dx.doi.org/10.1094/PDIS-06-20-1271-PDNDOI Listing
December 2020

Tritordeum breads are well tolerated with preference over gluten-free breads in non-celiac wheat-sensitive patients and its consumption induce changes in gut bacteria.

J Sci Food Agric 2020 Dec 4. Epub 2020 Dec 4.

Departamento de Mejora Genética Vegetal, Instituto de Agricultura Sostenible (IAS-CSIC), Córdoba, Spain.

Background: The ingestion of wheat and other cereals are related to several gut disorders. The specific components responsible for non-celiac wheat-sensitivity (NCWS) may include gluten and other compounds. Tritordeum is a new cereal derived from crossing durum wheat with a wild barley species, which differs from bread wheat in its gluten composition. In the present work, we examined the response of NCWS patients to tritordeum bread Gastrointestinal symptoms as well as tritordeum acceptability, gluten immunogenic peptides excretion, and the composition and structure of the intestinal microbiota were evaluated.

Results: Gastrointestinal symptoms of the subjects showed no significant change between the gluten-free bread and the tritordeum bread. Participating subjects rated tritordeum bread higher than the gluten-free bread. Analysis of the bacterial gut microbiota indicated that tritordeum consumption does not alter the global structure and composition of the intestinal microbiota, and only a few changes in some butyrate-producing bacteria were observed.

Conclusions: All the results derived from acceptability, biochemical and microbiological tests suggest that tritordeum may be tolerated by a sub-set of NCWS sufferers who do not require strict exclusion of gluten from their diet. © 2020 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.10982DOI Listing
December 2020

Phylogenetic inference enables reconstruction of a long-overlooked outbreak of almond leaf scorch disease (Xylella fastidiosa) in Europe.

Commun Biol 2020 Oct 9;3(1):560. Epub 2020 Oct 9.

Serveis de Millora Agrària i Pesquera, Govern de les illes Balears, 07009, Palma de Majorca, Spain.

The recent introductions of the bacterium Xylella fastidiosa (Xf) into Europe are linked to the international plant trade. However, both how and when these entries occurred remains poorly understood. Here, we show how almond scorch leaf disease, which affects ~79% of almond trees in Majorca (Spain) and was previously attributed to fungal pathogens, was in fact triggered by the introduction of Xf around 1993 and subsequently spread to grapevines (Pierce's disease). We reconstructed the progression of almond leaf scorch disease by using broad phylogenetic evidence supported by epidemiological data. Bayesian phylogenetic inference predicted that both Xf subspecies found in Majorca, fastidiosa ST1 (95% highest posterior density, HPD: 1990-1997) and multiplex ST81 (95% HPD: 1991-1998), shared their most recent common ancestors with Californian Xf populations associated with almonds and grapevines. Consistent with this chronology, Xf-DNA infections were identified in tree rings dating to 1998. Our findings uncover a previously unknown scenario in Europe and reveal how Pierce's disease reached the continent.
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http://dx.doi.org/10.1038/s42003-020-01284-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547738PMC
October 2020

Complete Circularized Genome Data of Two Spanish strains of (IVIA5235 and IVIA5901) Using Hybrid Assembly Approaches.

Phytopathology 2020 May 6;110(5):969-972. Epub 2020 Apr 6.

Institute for Sustainable Agriculture, Consejo superior de Investigaciones Científicas (CSIC), Córdoba, Spain.

is an economically important plant pathogenic bacterium of global importance associated, since 2013, with a devastating epidemic in olive trees in Italy. Since then, several outbreaks of this pathogen have been reported in other European member countries including Spain, France, and Portugal. In Spain, the three major subspecies (subsp. , and ) of the bacterium have been detected in the Balearic Islands, but only subspecies in the mainland (Alicante). We present the first complete genome sequences of two Spanish strains: subsp. IVIA5235 from Mallorca and subsp. IVIA5901 from Alicante, using Oxford Nanopore and Illumina sequence reads, and two hybrid approaches for genome assembly. These completed genomes will provide a resource to better understand the biology of these strains.
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http://dx.doi.org/10.1094/PHYTO-01-20-0012-ADOI Listing
May 2020

Culture-Dependent and Culture-Independent Characterization of the Olive Xylem Microbiota: Effect of Sap Extraction Methods.

Front Plant Sci 2019 21;10:1708. Epub 2020 Jan 21.

Institute for Sustainable Agriculture, Spanish National Research Council (CSIC), Córdoba, Spain.

Microbial endophytes are well known to protect host plants against pathogens, thus representing a promising strategy for the control of xylem-colonizing pathogens. To date, the vast majority of microbial communities inhabiting the olive xylem are unknown; therefore, this work pursues the characterization of the xylem-limited microbiome and determines whether the culture isolation medium, olive genotype, and the plant material used to analyze it can have an effect on the bacterial populations retrieved. Macerated xylem tissue and xylem sap extracted with the Scholander chamber from olive branches obtained from two cultivated and a wild olive genotypes were analyzed using culture-dependent and -independent approaches. In the culture-dependent approach using four solid culture media, a total of 261 bacterial isolates were identified after performing Sanger sequencing of 16S rRNA. Culturable bacteria clustered into 34 genera, with some effect of culture media for bacterial isolation. The cultivated bacteria belonged to four phyla and the most abundant genera included (18.8%), (16.4%), and (14.6%). On the other hand, in the culture-independent approach conducted using Illumina MiSeq 16S rRNA amplicon sequencing [next-generation sequencing (NGS)] of the xylem extracts, we identified a total of 48 operational taxonomic units (OTUs) belonging to five phyla, being (30.1%) (24.1%) and (22.4%) the most representative genera (>76% of reads). In addition, the results indicated significant differences in the bacterial communities detected in the xylem sap depending on the genotype of the olive tree studied and, to a minor extent, on the type of sap extraction method used. Among the total genera identified using NGS, 14 (41.2%) were recovered in the culture collection, whereas 20 (58.8%) in the culture collection were not captured by the NGS approach. Some of the xylem-inhabiting bacteria isolated are known biocontrol agents of plant pathogens, whereas for others little information is known and are first reported for olive. Consequently, the potential role of these bacteria in conferring olive tree protection against xylem pathogens should be explored in future research.
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http://dx.doi.org/10.3389/fpls.2019.01708DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6988092PMC
January 2020

Emergence of a Plant Pathogen in Europe Associated with Multiple Intercontinental Introductions.

Appl Environ Microbiol 2020 01 21;86(3). Epub 2020 Jan 21.

Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California, USA.

Pathogen introductions have led to numerous disease outbreaks in naive regions of the globe. The plant pathogen 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 subspecies 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 subspecies 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 subspecies strains originating from California is likely due to the clade itself being an introduction from subspecies 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 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 outbreaks. 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 subspecies and other outbreaks in Europe, such as subspecies and subspecies in Spain and subspecies in France. We present evidence of multiple introductions of subspecies , 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 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.
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http://dx.doi.org/10.1128/AEM.01521-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6974645PMC
January 2020

Insights Into the Effect of Defoliating-Pathotype Infection on the Content of Phenolic and Volatile Compounds Related to the Sensory Properties of Virgin Olive Oil.

Front Plant Sci 2019 5;10:232. Epub 2019 Mar 5.

Instituto de la Grasa, Spanish National Research Council (CSIC), Seville, Spain.

Verticillium wilt, caused by the defoliating pathotype of , is the most devastating soil-borne fungal disease of olive trees, and leads to low yields and high rates of tree mortality in highly susceptible cultivars. The disease is widely distributed throughout the Mediterranean olive-growing region and is one of the major limiting factors of olive oil production. Other than effects on crop yield, little is known about the effect of the disease on the content of volatile compounds and phenolics that are produced during the oil extraction process and determine virgin olive oil (VOO) quality and commercial value. Here, we aim to study the effect of Verticillium wilt of the olive tree on the content of phenolic and volatile compounds related to the sensory properties of VOO. Results showed that synthesis of six and five straight-chain carbon volatile compounds were higher and lower, respectively, in oils extracted from infected trees. Pathogen infection affected volatile compounds known to be contributors to VOO aroma: average content of one of the main positive contributors to VOO aroma, ()-hex-2-enal, was 38% higher in oils extracted from infected trees, whereas average content of the main unpleasant volatile compound, pent-1-en-3-one, was almost 50% lower. In contrast, there was a clear effect of pathogen infection on the content of compounds responsible for VOO taste, where average content of the main bitterness contributor, oleuropein aglycone, was 18% lower in oil extracted from infected plants, and content of oleocanthal, the main contributor to pungency, was 26% lower. We believe this is the first evidence of the effect of Verticillium wilt infection of olive trees on volatile compounds and phenolics that are responsible of the aroma, taste, and commercial value of VOO.
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http://dx.doi.org/10.3389/fpls.2019.00232DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413673PMC
March 2019

Sex Differences in the Gut Microbiota as Potential Determinants of Gender Predisposition to Disease.

Mol Nutr Food Res 2019 04 13;63(7):e1800870. Epub 2019 Feb 13.

Lipids and Atherosclerosis Research Unit, Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Cordoba, 14004, Spain.

Scope: Dysbiosis of gut microbiota is involved in metabolic syndrome (MetS) development, which has a different incidence between men (M) and women (W). The differences in gut microbiota in MetS patients are explored according to gender, and whether consuming two healthy diets, Mediterranean (MED) and low-fat (LF), may, over time, differentially shape the gut microbiota dysbiosis according to gender is evaluated.

Materials And Methods: All the women from the CORDIOPREV study whose feces samples were available and a similar number of men, matched by the main metabolic variables (N = 246, 123 women and 123 men), and categorized according to the presence or not of MetS are included. Gut microbiota is analyzed at baseline and after 3 years of dietary intervention.

Results: Higher abundance of Collinsella, Alistipes, Anaerotruncus, and Phascolarctobacterium genera is observed in MetS-W than in MetS-M, whereas the abundance of Faecalibacterium and Prevotella genera is higher in MetS-M than in MetS-W. Moreover, higher levels of Desulfovibrio, Roseburia, and Holdemania are observed in men than in women after the consumption of the LF diet.

Conclusion: The results suggest the potential involvement of differences in gut microbiota in the unequal incidence of metabolic diseases between genders, and a sex-dependent effect on shaping the gut microbiota according to diet.
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http://dx.doi.org/10.1002/mnfr.201800870DOI Listing
April 2019

Draft Genome Resources of Two Strains ("ESVL" and "IVIA5901") of Xylella fastidiosa Associated with Almond Leaf Scorch Disease in Alicante, Spain.

Phytopathology 2019 Feb 28;109(2):219-221. Epub 2018 Dec 28.

2 Institute for Sustainable Agriculture, Consejo Superior de Investigaciones Científicas (IAS-CSIC), 14004 Córdoba, Spain.

An outbreak of Xylella fastidiosa subsp. multiplex sequence type ST6 was discovered in 2017 in mainland Spain affecting almond trees. Two cultured almond strains, "ESVL" and "IVIA5901," were subjected to high throughput sequencing and the draft genomes assembled. Phylogenetic analysis conclusively indicated they belong to the subspecies multiplex, and pairwise comparisons of the chromosomal genomes showed an average nucleotide identity higher than 99%. Interestingly, the two strains differ for the presence of the plasmids pXF64-Hb_ESVL and pUCLA-ESVL detected only in the ESVL strain. The availability of these draft genomes contribute to extend the European genomic sequence dataset, a first step toward setting new research to elucidate the pathway of introduction and spread of the numerous strains of this subspecies so far detected in Europe.
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http://dx.doi.org/10.1094/PHYTO-09-18-0328-ADOI Listing
February 2019

The Dietary Intervention of Transgenic Low-Gliadin Wheat Bread in Patients with Non-Celiac Gluten Sensitivity (NCGS) Showed No Differences with Gluten Free Diet (GFD) but Provides Better Gut Microbiota Profile.

Nutrients 2018 Dec 12;10(12). Epub 2018 Dec 12.

Departamento de Mejora Genética Vegetal, Instituto de Agricultura Sostenible (IAS-CSIC), 14004 Córdoba, Spain.

The study evaluated the symptoms, acceptance, and digestibility of bread made from transgenic low-gliadin wheat, in comparison with gluten free bread, in Non-coeliac gluten sensitivity (NCGS) patients, considering clinical/sensory parameters and gut microbiota composition. This study was performed in two phases of seven days each, comprising a basal phase with gluten free bread and an E82 phase with low-gliadin bread. Gastrointestinal clinical symptoms were evaluated using the Gastrointestinal Symptom Rating Scale (GSRS) questionnaire, and stool samples were collected for gluten immunogenic peptides (GIP) determination and the extraction of gut microbial DNA. For the basal and E82 phases, seven and five patients, respectively, showed undetectable GIPs content. The bacterial 16S rRNA gene V1-V2 hypervariable regions were sequenced using the Illumina MiSeq platform and downstream analysis was done using a Quantitative Insights into Microbial Ecology (QIIME) pipeline. No significant differences in the GSRS questionnaires were observed between the two phases. However, we observed a significantly lower abundance of some gut genera , , , , , and and a significantly higher abundance of and genera during the E82 phase compared with the basal phase. The consumption of low-gliadin bread E82 by NCGS subjects induced potentially positive changes in the gut microbiota composition, increasing the butyrate-producing bacteria and favoring a microbial profile that is suggested to have a key role in the maintenance or improvement of gut permeability.
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http://dx.doi.org/10.3390/nu10121964DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6316513PMC
December 2018

Draft Genome Sequence of Xylella fastidiosa subsp. Strain IVIA5235, Isolated from Prunus avium in Mallorca Island, Spain.

Microbiol Resour Announc 2018 Oct 11;7(14). Epub 2018 Oct 11.

Dipartimento di Scienze del Suolo della Pianta e degli Alimenti, Università degli Studi di Bari Aldo Moro, Bari, Italy.

We report the complete annotated genome sequence of the plant-pathogenic bacterium Xylella fastidiosa subsp. strain IVIA5235. This strain was recovered from a cherry tree in Mallorca, Spain.
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http://dx.doi.org/10.1128/MRA.01222-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6256637PMC
October 2018

Influence of gender and menopausal status on gut microbiota.

Maturitas 2018 Oct 19;116:43-53. Epub 2018 Jul 19.

Lipids and Atherosclerosis Research Unit, Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Cordoba, Spain; CIBER Fisiopatología de la Obesidad y Nutricion (CIBEROBN), Instituto de Salud Carlos III, Cordoba, Spain. Electronic address:

Objectives: We explore the differences in the gut microbiota associated with gender and hormonal status.

Study Design: We included 76 individuals in this study: 17 pre-menopausal women, 19 men matched by age, as a control group for the pre-menopausal women, 20 post-menopausal women and 20 men matched by age as a control group for the post-menopausal women; all 4 groups were also matched by body mass index (BMI) and nutritional background.

Main Measurements: We analyzed the differences in the gut microbiota, endotoxemia, intestinal incretins, pro-inflammatory cytokines, and plasma levels of energy homeostasis regulatory hormones between pre- and post-menopausal women and compared them with their respective male control groups.

Results: We found a higher Firmicutes/Bacteroidetes ratio, a higher relative abundance of Lachnospira and Roseburia, and higher GLP-1 plasma levels in pre-menopausal women than in post-menopausal women, who had similar levels to men. In contrast, we observed a lower relative abundance of the Prevotella, Parabacteroides and Bilophila genera, and IL-6 and MCP-1 plasma levels in pre-menopausal women than in post-menopausal women, who had similar levels to the men. We also found higher GiP and leptin plasma levels in women than in men, irrespective of the menopausal status of the women. In addition, adiponectin levels were higher in pre-menopausal women than in their corresponding age-matched male control group.

Conclusions: Our results suggest that the differences in the composition of gut microbiota between genders and between women of different hormonal status may be related to the sexual dimorphism observed in the incidence of metabolic diseases and their co-morbidities.
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http://dx.doi.org/10.1016/j.maturitas.2018.07.008DOI Listing
October 2018

Consumption of Two Healthy Dietary Patterns Restored Microbiota Dysbiosis in Obese Patients with Metabolic Dysfunction.

Mol Nutr Food Res 2017 12 7;61(12). Epub 2017 Nov 7.

Lipids and Atherosclerosis Unit, GC9 Nutrigenomics, Institute Maimonides for Biomedical Research of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Cordoba, Spain.

Scope: The consumption of two healthy diets (Mediterranean (MED) and low-fat (LF) diets) may restore the gut microbiome dysbiosis in obese patients depending on the degree of metabolic dysfunction.

Methods And Results: The differences in bacterial community at baseline and after 2 years of dietary intervention of 106 subjects from the CORDIOPREV study were analyzed, 33 of whom were obese patients with severe metabolic disease (5 criteria for metabolic syndrome) (MetS-OB), 32 obese patients without metabolic dysfunction (2 or less criteria for metabolic syndrome) (NonMetS-OB) and 41 non-obese subjects (NonMetS-NonOB). Our study showed a marked dysbiosis in people with severe metabolic disease (Met-OB), compared with obese people without MetS (NonMetS-OB) and non-obese people (NonMetS-NonOB). This disbiotic pattern was reversed by consumption of both MED (35% of calories as fat (22% MUFA fat, 6% PUFA fat and <10% saturated fat) or LF (<30% total fat (<10% saturated fat, 12%-14% MUFA fat and 6-8% PUFA fat) diets, whereas no significant microbiota changes were observed in NonMetS-NonOB and NonMetS-OB groups.

Conclusion: Our results suggest that the chronic intake of two healthy dietary patterns partially restores the gut microbiome dysbiosis in obese patients with coronary heart disease, depending on the degree of metabolic dysfunction.
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http://dx.doi.org/10.1002/mnfr.201700300DOI Listing
December 2017

Genome-Wide Analysis Provides Evidence on the Genetic Relatedness of the Emergent Xylella fastidiosa Genotype in Italy to Isolates from Central America.

Phytopathology 2017 07 31;107(7):816-827. Epub 2017 May 31.

First, third, and fifth authors: Università degli Studi di Bari Aldo Moro, Dipartimento di Scienze del Suolo della Pianta e degli Alimenti, via Amendola 165/A, Bari, Italy; second, fourth, seventh, and tenth authors: Consiglio Nazionale delle Ricerche, Istituto per la Protezione Sostenibile delle Piante, Bari, via Amendola 122/D, Bari, Italy; sixth author: Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, 94720-3114; eighth author: Institute for Sustainable Agriculture, Consejo Superior de Investigaciones Científicas, 14004 Córdoba, Spain; and ninth author: Centro de Investigación en Enfermedades Tropicales (CIET), Facultad de Microbiología, Universidad de Costa Rica, 2060 San José, Costa Rica.

Xylella fastidiosa is a plant-pathogenic bacterium recently introduced in Europe that is causing decline in olive trees in the South of Italy. Genetic studies have consistently shown that the bacterial genotype recovered from infected olive trees belongs to the sequence type ST53 within subspecies pauca. This genotype, ST53, has also been reported to occur in Costa Rica. The ancestry of ST53 was recently clarified, showing it contains alleles that are monophyletic with those of subsp. pauca in South America. To more robustly determine the phylogenetic placement of ST53 within X. fastidiosa, we performed a comparative analysis based on single nucleotide polymorphisms (SNPs) and the study of the pan-genome of the 27 currently public available whole genome sequences of X. fastidiosa. The resulting maximum-parsimony and maximum likelihood trees constructed using the SNPs and the pan-genome analysis are consistent with previously described X. fastidiosa taxonomy, distinguishing the subsp. fastidiosa, multiplex, pauca, sandyi, and morus. Within the subsp. pauca, the Italian and three Costa Rican isolates, all belonging to ST53, formed a compact phylotype in a clade divergent from the South American pauca isolates, also distinct from the recently described coffee isolate CFBP8072 imported into Europe from Ecuador. These findings were also supported by the gene characterization of a conjugative plasmid shared by all the four ST53 isolates. Furthermore, isolates of the ST53 clade possess an exclusive locus encoding a putative ATP-binding protein belonging to the family of histidine kinase-like ATPase gene, which is not present in isolates from the subspecies multiplex, sandyi, and pauca, but was detected in ST21 isolates of the subspecies fastidiosa from Costa Rica. The clustering and distinctiveness of the ST53 isolates supports the hypothesis of their common origin, and the limited genetic diversity among these isolates suggests this is an emerging clade within subsp. pauca.
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http://dx.doi.org/10.1094/PHYTO-12-16-0420-RDOI Listing
July 2017

Enhancement of the Knowledge on Fungal Communities in Directly Brined Aloreña de Málaga Green Olive Fermentations by Metabarcoding Analysis.

PLoS One 2016 16;11(9):e0163135. Epub 2016 Sep 16.

Crop Protection Department, Institute for Sustainable Agriculture (IAS-CSIC), Avenida Menéndez Pidal s/n Campus Alameda del Obispo, 14004, Cordoba, Spain.

Nowadays, our knowledge of the fungal biodiversity in fermented vegetables is limited although these microorganisms could have a great influence on the quality and safety of this kind of food. This work uses a metagenetic approach to obtain basic knowledge of the fungal community ecology during the course of fermentation of natural Aloreña de Málaga table olives, from reception of raw material to edible fruits. For this purpose, samples of brines and fruits were collected from two industries in Guadalhorce Valley (Málaga, Spain) at different moments of fermentation (0, 7, 30 and 120 days). The physicochemical and microbial counts performed during fermentation showed the typical evolution of this type of processes, mainly dominated by yeasts in apparent absence of Enterobacteriaceae and Lactobacillaceae. High-throughput barcoded pyrosequencing analysis of ITS1-5.8S-ITS2 region showed a low biodiversity of the fungal community, with the presence at 97% identity of 29 different fungal genera included in 105 operational taxonomic units (OTUs). The most important genera in the raw material at the moment of reception in the industry were Penicillium, Cladosporium, Malassezia, and Candida, whilst after 4 months of fermentation in brines Zygotorulaspora and Pichia were predominant, whereas in fruits were Candida, Penicillium, Debaryomyces and Saccharomyces. The fungal genera Penicillium, Pichia, and Zygotorulaspora were shared among the three types of substrates during all the course of fermentation, representing the core fungal population for this table olive specialty. A phylogenetic analysis of the ITS sequences allowed a more accurate assignment of diverse OTUs to Pichia manshurica, Candida parapsilosis/C. tropicalis, Candida diddensiae, and Citeromyces nyonensis clades. This study highlights the existence of a complex fungal consortium in olive fermentations including phytopathogenic, saprofitic, spoilage and fermentative genera. Insights into the ecology, identification and quantification of fungi species in olive fermentation will facilitate the design of new strategies to improve the quality and safety of this fermented vegetable.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0163135PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5026345PMC
August 2017

Detection and Quantification of the Entomopathogenic Fungal Endophyte Beauveria bassiana in Plants by Nested and Quantitative PCR.

Methods Mol Biol 2016 ;1477:161-6

Department of Agricultural and Forest Science and Resources, University of Córdoba (UCO), Campus de Rabanales, CeiA3, P.O. Box 3048, 14080, Córdoba, Spain.

The described protocol allows detecting as low as 10 fg the entomopathogenic fungal endophyte Beauveria bassiana in host plants by using a two-step nested PCR with the ITS1F/ITS4 and BB.fw and BB.rv primer pairs. On the other hand, a qPCR protocol using BB.fw and BB.rv primers is also available allowing the quantification of up to 26 fg of B. bassiana DNA per 20 ng of leaf DNA.
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http://dx.doi.org/10.1007/978-1-4939-6367-6_12DOI Listing
December 2017

Intestinal Microbiota Is Influenced by Gender and Body Mass Index.

PLoS One 2016 26;11(5):e0154090. Epub 2016 May 26.

Lipids and Atherosclerosis Unit, GC9 Nutrigenomics. IMIBIC/Reina Sofia University Hospital/University of Cordoba, Cordoba, Spain.

Intestinal microbiota changes are associated with the development of obesity. However, studies in humans have generated conflicting results due to high inter-individual heterogeneity in terms of diet, age, and hormonal factors, and the largely unexplored influence of gender. In this work, we aimed to identify differential gut microbiota signatures associated with obesity, as a function of gender and changes in body mass index (BMI). Differences in the bacterial community structure were analyzed by 16S sequencing in 39 men and 36 post-menopausal women, who had similar dietary background, matched by age and stratified according to the BMI. We observed that the abundance of the Bacteroides genus was lower in men than in women (P<0.001, Q = 0.002) when BMI was > 33. In fact, the abundance of this genus decreased in men with an increase in BMI (P<0.001, Q<0.001). However, in women, it remained unchanged within the different ranges of BMI. We observed a higher presence of Veillonella (84.6% vs. 47.2%; X2 test P = 0.001, Q = 0.019) and Methanobrevibacter genera (84.6% vs. 47.2%; X2 test P = 0.002, Q = 0.026) in fecal samples in men compared to women. We also observed that the abundance of Bilophila was lower in men compared to women regardless of BMI (P = 0.002, Q = 0.041). Additionally, after correcting for age and sex, 66 bacterial taxa at the genus level were found to be associated with BMI and plasma lipids. Microbiota explained at P = 0.001, 31.17% variation in BMI, 29.04% in triglycerides, 33.70% in high-density lipoproteins, 46.86% in low-density lipoproteins, and 28.55% in total cholesterol. Our results suggest that gut microbiota may differ between men and women, and that these differences may be influenced by the grade of obesity. The divergence in gut microbiota observed between men and women might have a dominant role in the definition of gender differences in the prevalence of metabolic and intestinal inflammatory diseases.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154090PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4881937PMC
July 2017

Two Healthy Diets Modulate Gut Microbial Community Improving Insulin Sensitivity in a Human Obese Population.

J Clin Endocrinol Metab 2016 Jan 27;101(1):233-42. Epub 2015 Oct 27.

Lipids and Atherosclerosis Unit (C.H., O.A.R.-Z., J.F.A.-D., F.G.-D., P.P.-M., J.D.-L., G.M.Q.-N., J.L.-M., A.C., F.P.-J.), GC9 Nutrigenomics. IMIBIC/Reina Sofia University Hospital/University of Cordoba, 14004 Cordoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (C.H., O.A.R.-Z., J.F.A.-D., F.G.-D., P.P.-M., J.D.-L., G.M.Q.-N., F.J.T., J.L.-M., A.C., F.P.-J.), Instituto de Salud Carlos III, 14004 Cordoba, Spain; Instituto de Agricultura Sostenible (M.M.-B., B.B.L.), Consejo Superior de Investigaciones Científicas, 14004 Cordoba, Spain; and Endocrinology and Nutrition Service (F.J.T.). Hospital Virgen de la Victoria, 29010 Málaga, Spain.

Context: Gut microbiota, which acts collectively as a fully integrated organ in the host metabolism, can be shaped by long-term dietary interventions after a specific diet.

Objective: The aim was to study the changes in microbiota after 1 year's consumption of a Mediterranean diet (Med diet) or a low-fat, high-complex carbohydrate diet (LFHCC diet) in an obese population.

Design: Participants were randomized to receive the Med diet (35% fat, 22% monounsaturated) and the LFHCC diet (28% fat, 12% monounsaturated).

Setting And Participants: The study was conducted in 20 obese patients (men) within the Coronary Diet Intervention With Olive Oil and Cardiovascular Prevention (CORDIOPREV) study, an ongoing prospective, randomized, opened, controlled trial in patients with coronary heart disease.

Main Outcome Measure: We evaluated the bacterial composition and its relationship with the whole fecal and plasma metabolome.

Results: The LFHCC diet increased the Prevotella and decreased the Roseburia genera, whereas the Med diet decreased the Prevotella and increased the Roseburia and Oscillospira genera (P = .028, .002, and .016, respectively). The abundance of Parabacteroides distasonis (P = .025) and Faecalibacterium prausnitzii (P = .020) increased after long-term consumption of the Med diet and the LFHCC diet, respectively. The changes in the abundance of 7 of 572 metabolites found in feces, including mainly amino acid, peptide, and sphingolipid metabolism, could be linked to the changes in the gut microbiota.

Conclusions: Our results suggest that long-term consumption of the Med and LFHCC diets exerts a protective effect on the development of type 2 diabetes by different specific changes in the gut microbiota, increasing the abundance of the Roseburia genus and F. prausnitzii, respectively.
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http://dx.doi.org/10.1210/jc.2015-3351DOI Listing
January 2016

Combined use of a new SNP-based assay and multilocus SSR markers to assess genetic diversity of Xylella fastidiosa subsp. pauca infecting citrus and coffee plants.

Int Microbiol 2015 Mar;18(1):13-24

Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), 14080 Córdoba, Spain.

Two haplotypes of Xylella fastidiosa subsp. pauca (Xfp) that correlated with their host of origin were identified in a collection of 90 isolates infecting citrus and coffee plants in Brazil, based on a single-nucleotide polymorphism in the gyrB sequence. A new single-nucleotide primer extension (SNuPE) protocol was designed for rapid identification of Xfp according to the host source. The protocol proved to be robust for the prediction of the Xfp host source in blind tests using DNA from cultures of the bacterium, infected plants, and insect vectors allowed to feed on Xfp-infected citrus plants. AMOVA and STRUCTURE analyses of microsatellite data separated most Xfp populations on the basis of their host source, indicating that they were genetically distinct. The combined use of the SNaPshot protocol and three previously developed multilocus SSR markers showed that two haplotypes and distinct isolates of Xfp infect citrus and coffee in Brazil and that multiple, genetically different isolates can be present in a single orchard or infect a single tree. This combined approach will be very useful in studies of the epidemiology of Xfp-induced diseases, host specificity of bacterial genotypes, the occurrence of Xfp host jumping, vector feeding habits, etc., in economically important cultivated plants or weed host reservoirs of Xfp in Brazil and elsewhere.
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http://dx.doi.org/10.2436/20.1501.01.230DOI Listing
March 2015

The gut microbial community in metabolic syndrome patients is modified by diet.

J Nutr Biochem 2016 Jan 20;27:27-31. Epub 2015 Aug 20.

Lipids and Atherosclerosis Unit, IMIBIC/Reina Sofia University Hospital/University of Cordoba, Cordoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Santiago de Compostela, Spain.

Intestinal microbiota changes may be involved in the development of metabolic syndrome (MetS), which is a multicomponent disorder frequently associated with obesity. The aim of this study was to test the effect of consuming two healthy diets: a Mediterranean diet and a low-fat high-carbohydrate diet, for 2years in the gut microbiota of MetS patients and those in the control group. We analyzed the differences in the bacterial community structure between the groups after 2years of dietary intervention (Mediterranean or low-fat diet) through quantitative polymerase chain reaction using primers, targeting specific bacterial taxa. We observed, at basal time, that the abundance of Bacteroides, Eubacterium and Lactobacillus genera is lower in the control group than in MetS patients, while Bacteroides fragilis group, Parabacteroides distasonis, Bacteroides thetaiotaomicron, Faecalibacterium prausnitzii, Fusobacterium nucleatum, Bifidobacterium longum, Bifidobacterium adolescentis, Ruminococcus flavefaciens subgroup and Eubacterium rectale are depleted in MetS patients (all P values <.05). Additionally, we found that long-term consumption of Mediterranean diet partially restores the population of P. distasonis, B. thetaiotaomicron, F. prausnitzii, B. adolescentis and B. longum in MetS patients (all P values <.05). Our results suggest that the Mediterranean diet could be a useful tool to restore potentially beneficial members of the gut microbiota, although the stability of these changes over time still remains to be assessed.
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http://dx.doi.org/10.1016/j.jnutbio.2015.08.011DOI Listing
January 2016

Influence of edaphic, climatic, and agronomic factors on the composition and abundance of nitrifying microorganisms in the rhizosphere of commercial olive crops.

PLoS One 2015 7;10(5):e0125787. Epub 2015 May 7.

Biogeodynamics & Biodiversity Group, Centro de Estudios Avanzados de Blanes, CEAB-CSIC, Blanes, Girona.

The microbial ecology of the nitrogen cycle in agricultural soils is an issue of major interest. We hypothesized a major effect by farm management systems (mineral versus organic fertilizers) and a minor influence of soil texture and plant variety on the composition and abundance of microbial nitrifiers. We explored changes in composition (16S rRNA gene) of ammonia-oxidizing archaea (AOA), bacteria (AOB), and nitrite-oxidizing bacteria (NOB), and in abundance of AOA and AOB (qPCR of amoA genes) in the rhizosphere of 96 olive orchards differing in climatic conditions, agricultural practices, soil properties, and olive variety. Majority of archaea were 1.1b thaumarchaeota (soil crenarchaeotic group, SCG) closely related to the AOA genus Nitrososphaera. Most AOB (97%) were identical to Nitrosospira tenuis and most NOB (76%) were closely related to Nitrospira sp. Common factors shaping nitrifiers assemblage composition were pH, soil texture, and olive variety. AOB abundance was positively correlated with altitude, pH, and clay content, whereas AOA abundances showed significant relationships with organic nitrogen content and exchangeable K. The abundances of AOA differed significantly among soil textures and olive varieties, and those of AOB among soil management systems and olive varieties. Overall, we observed minor effects by orchard management system, soil cover crop practices, plantation age, or soil organic matter content, and major influence of soil texture, pH, and olive tree variety.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125787PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4423868PMC
April 2016

Plant genotype-specific archaeal and bacterial endophytes but similar Bacillus antagonists colonize Mediterranean olive trees.

Front Microbiol 2015 3;6:138. Epub 2015 Mar 3.

Institute of Environmental Biotechnology, Graz University of Technology Graz, Austria.

Endophytes have an intimate and often symbiotic interaction with their hosts. Less is known about the composition and function of endophytes in trees. In order to evaluate our hypothesis that plant genotype and origin have a strong impact on both, endophytes of leaves from 10 Olea europaea L. cultivars from the Mediterranean basin growing at a single agricultural site in Spain and from nine wild olive trees located in natural habitats in Greece, Cyprus, and on Madeira Island were studied. The composition of the bacterial endophytic communities as revealed by 16S rRNA gene amplicon sequencing and the subsequent PCoA analysis showed a strong correlation to the plant genotypes. The bacterial distribution patterns were congruent with the plant origins in "Eastern" and "Western" areas of the Mediterranean basin. Subsequently, the endophytic microbiome of wild olives was shown to be closely related to those of cultivated olives of the corresponding geographic origins. The olive leaf endosphere harbored mostly Proteobacteria, followed by Firmicutes, Actinobacteria, and Bacteroidetes. The detection of a high portion of archaeal taxa belonging to the phyla Thaumarchaeota, Crenarchaeota, and Euryarchaeota in the amplicon libraries was an unexpected discovery, which was confirmed by quantitative real-time PCR revealing an archaeal portion of up to 35.8%. Although the function of these Archaea for their host plant remains speculative, this finding suggests a significant relevance of archaeal endophytes for plant-microbe interactions. In addition, the antagonistic potential of culturable endophytes was determined; all isolates with antagonistic activity against the olive-pathogenic fungus Verticillium dahliae Kleb. belong to Bacillus amyloliquefaciens. In contrast to the specific global structural diversity, BOX-fingerprints of the antagonistic Bacillus isolates were highly similar and independent of the olive genotype from which they were isolated.
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http://dx.doi.org/10.3389/fmicb.2015.00138DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4347506PMC
March 2015

Organic amendments to avocado crops induce suppressiveness and influence the composition and activity of soil microbial communities.

Appl Environ Microbiol 2015 May 13;81(10):3405-18. Epub 2015 Mar 13.

Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora," Universidad de Málaga, Consejo Superior de Investigaciones Científicas, and Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain

One of the main avocado diseases in southern Spain is white root rot caused by the fungus Rosellinia necatrix Prill. The use of organic soil amendments to enhance the suppressiveness of natural soil is an inviting approach that has successfully controlled other soilborne pathogens. This study tested the suppressive capacity of different organic amendments against R. necatrix and analyzed their effects on soil microbial communities and enzymatic activities. Two-year-old avocado trees were grown in soil treated with composted organic amendments and then used for inoculation assays. All of the organic treatments reduced disease development in comparison to unamended control soil, especially yard waste (YW) and almond shells (AS). The YW had a strong effect on microbial communities in bulk soil and produced larger population levels and diversity, higher hydrolytic activity and strong changes in the bacterial community composition of bulk soil, suggesting a mechanism of general suppression. Amendment with AS induced more subtle changes in bacterial community composition and specific enzymatic activities, with the strongest effects observed in the rhizosphere. Even if the effect was not strong, the changes caused by AS in bulk soil microbiota were related to the direct inhibition of R. necatrix by this amendment, most likely being connected to specific populations able to recolonize conducive soil after pasteurization. All of the organic amendments assayed in this study were able to suppress white root rot, although their suppressiveness appears to be mediated differentially.
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http://dx.doi.org/10.1128/AEM.03787-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4407234PMC
May 2015

Soil properties and olive cultivar determine the structure and diversity of plant-parasitic nematode communities infesting olive orchards soils in southern Spain.

PLoS One 2015 27;10(1):e0116890. Epub 2015 Jan 27.

Instituto de Agricultura Sostenible (IAS), Consejo Superior de Investigaciones Científicas (CSIC), Apartado 4084, 14080, Córdoba, Spain.

This work has studied for the first time the structure and diversity of plant-parasitic nematodes (PPNs) infesting olive orchard soils in a wide-region in Spain that included 92 locations. It aims at determining which agronomical or environmental factors associated to the olive orchards are the main drivers of the PPNs community structure and diversity. Classical morphological and morphometric identification methods were used to determine the frequency and densities of PPNs. Thirteen families, 34 genera and 77 species of PPNs were identified. The highest diversity was found in Helicotylenchus genus, with six species previously reported in Spain and with H. oleae being a first report. Neodolichorhynchus microphasmis and Diptenchus sp., Diphtherophora sp., and Discotylenchus sp., usually considered fungal feeders, were also reported for the first time associated to olive rhizosphere. PPNs abundance ranged from 66 to 16,288 individuals/500-cm3 of soil with Helicotylenchus digonicus being the most prevalent species, followed by Filenchus sp., Merlinius brevidens and Xiphinema pachtaicum. Nematode abundance and diversity indexes were influenced by olive cultivar, and orchard and soil management practices; while olive variety and soil texture were the main factors driving PPN community composition. Soil physicochemical properties and climatic characteristics most strongly associated to the PPN community composition included pH, sand content and exchangeable K, and maximum and minimum average temperature of the sampled locations. Our data suggests that there is a high diversity of PPNs associated to olive in Southern Spain that can exert different damage to olive roots depending on the olive variety and their abundance. Further analysis to determine the resistance levels of most common olive varieties to the prevalent PPNs in Spain will help to choose the most appropriate ones for the establishment of new plantations. This choice will take into consideration the specific soils and environments where those olive varieties will be established.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116890PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4308072PMC
January 2016

Disentangling Peronospora on Papaver: phylogenetics, taxonomy, nomenclature and host range of downy mildew of opium poppy (Papaver somniferum) and related species.

PLoS One 2014 7;9(5):e96838. Epub 2014 May 7.

Department of Crop Protection, Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), Córdoba, Spain.

Based on sequence data from ITS rDNA, cox1 and cox2, six Peronospora species are recognised as phylogenetically distinct on various Papaver species. The host ranges of the four already described species P. arborescens, P. argemones, P. cristata and P. meconopsidis are clarified. Based on sequence data and morphology, two new species, P. apula and P. somniferi, are described from Papaver apulum and P. somniferum, respectively. The second Peronospora species parasitizing Papaver somniferum, that was only recently recorded as Peronospora cristata from Tasmania, is shown to represent a distinct taxon, P. meconopsidis, originally described from Meconopsis cambrica. It is shown that P. meconopsidis on Papaver somniferum is also present and widespread in Europe and Asia, but has been overlooked due to confusion with P. somniferi and due to less prominent, localized disease symptoms. Oospores are reported for the first time for P. meconopsidis from Asian collections on Papaver somniferum. Morphological descriptions, illustrations and a key are provided for all described Peronospora species on Papaver. cox1 and cox2 sequence data are confirmed as equally good barcoding loci for reliable Peronospora species identification, whereas ITS rDNA does sometimes not resolve species boundaries. Molecular phylogenetic data reveal high host specificity of Peronospora on Papaver, which has the important phytopathological implication that wild Papaver spp. cannot play any role as primary inoculum source for downy mildew epidemics in cultivated opium poppy crops.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096838PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4013089PMC
June 2015

Arbuscular mycorhizal fungi associated with the olive crop across the Andalusian landscape: factors driving community differentiation.

PLoS One 2014 5;9(5):e96397. Epub 2014 May 5.

Department of Crop Protection, Institute for Sustainable Agriculture (IAS-CSIC), Cordoba, Spain.

Background: In the last years, many olive plantations in southern Spain have been mediated by the use of self-rooted planting stocks, which have incorporated commercial AMF during the nursery period to facilitate their establishment. However, this was practised without enough knowledge on the effect of cropping practices and environment on the biodiversity of AMF in olive orchards in Spain.

Methodology/principal Findings: Two culture-independent molecular methods were used to study the AMF communities associated with olive in a wide-region analysis in southern Spain including 96 olive locations. The use of T-RFLP and pyrosequencing analysis of rDNA sequences provided the first evidence of an effect of agronomic and climatic characteristics, and soil physicochemical properties on AMF community composition associated with olive. Thus, the factors most strongly associated to AMF distribution varied according to the technique but included among the studied agronomic characteristics the cultivar genotype and age of plantation and the irrigation regimen but not the orchard management system or presence of a cover crop to prevent soil erosion. Soil physicochemical properties and climatic characteristics most strongly associated to the AMF community composition included pH, textural components and nutrient contents of soil, and average evapotranspiration, rainfall and minimum temperature of the sampled locations. Pyrosequencing analysis revealed 33 AMF OTUs belonging to five families, with Archaeospora spp., Diversispora spp. and Paraglomus spp., being first records in olive. Interestingly, two of the most frequent OTUs included a diverse group of Claroideoglomeraceae and Glomeraceae sequences, not assigned to any known AMF species commonly used as inoculants in olive during nursery propagation.

Conclusions/significance: Our data suggests that AMF can exert higher host specificity in olive than previously thought, which may have important implications for redirecting the olive nursery process in the future as well as to take into consideration the specific soils and environments where the mycorrhized olive trees will be established.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096397PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4010464PMC
July 2015

Quantitative and microscopic assessment of compatible and incompatible interactions between chickpea cultivars and Fusarium oxysporum f. sp. ciceris races.

PLoS One 2013 16;8(4):e61360. Epub 2013 Apr 16.

College of Agriculture and Forestry, University of Córdoba, Campus de Excelencia Internacional Agroalimentario ceiA3, Córdoba, Spain.

Background: Fusarium wilt caused by Fusarium oxysporum f. sp. ciceris, a main threat to global chickpea production, is managed mainly by resistant cultivars whose efficiency is curtailed by Fusarium oxysporum f. sp. ciceris races.

Methodology: We characterized compatible and incompatible interactions by assessing the spatial-temporal pattern of infection and colonization of chickpea cvs. P-2245, JG-62 and WR-315 by Fusarium oxysporum f. sp. ciceris races 0 and 5 labeled with ZsGreen fluorescent protein using confocal laser scanning microscopy.

Findings: The two races colonized the host root surface in both interactions with preferential colonization of the root apex and subapical root zone. In compatible interactions, the pathogen grew intercellularly in the root cortex, reached the xylem, and progressed upwards in the stem xylem, being the rate and intensity of stem colonization directly related with the degree of compatibility among Fusarium oxysporum f. sp. ciceris races and chickpea cultivars. In incompatible interactions, race 0 invaded and colonized 'JG-62' xylem vessels of root and stem but in 'WR-315', it remained in the intercellular spaces of the root cortex failing to reach the xylem, whereas race 5 progressed up to the hypocotyl. However, all incompatible interactions were asymptomatic.

Conclusions: The differential patterns of colonization of chickpea cultivars by Fusarium oxysporum f. sp. ciceris races may be related to the operation of multiple resistance mechanisms.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0061360PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3629054PMC
November 2013

Sequence variation in two protein-coding genes correlates with mycelial compatibility groupings in Sclerotium rolfsii.

Phytopathology 2013 May;103(5):479-87

Instituto de Agricultura Sostenible, Cordoba, Spain.

Populations of Sclerotium rolfsii, the causal organism of Sclerotium root-rot on a wide range of hosts, can be placed into mycelial compatibility groups (MCGs). In this study, we evaluated three different molecular approaches to unequivocally identify each of 12 previously identified MCGs. These included restriction fragment length polymorphism (RFLP) patterns of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (rDNA) and sequence analysis of two protein-coding genes: translation elongation factor 1α (EF1α) and RNA polymerase II subunit two (RPB2). A collection of 238 single-sclerotial isolates representing 12 MCGs of S. rolfsii were obtained from diseased sugar beet plants from Chile, Italy, Portugal, and Spain. ITS-RFLP analysis using four restriction enzymes (AluI, HpaII, RsaI, and MboI) displayed a low degree of variability among MCGs. Only three different restriction profiles were identified among S. rolfsii isolates, with no correlation to MCG or to geographic origin. Based on nucleotide polymorphisms, the RPB2 gene was more variable among MCGs compared with the EF1α gene. Thus, 10 of 12 MCGs could be characterized utilizing the RPB2 region only, while the EF1α region resolved 7 MCGs. However, the analysis of combined partial sequences of EF1α and RPB2 genes allowed discrimination among each of the 12 MCGs. All isolates belonging to the same MCG showed identical nucleotide sequences that differed by at least in one nucleotide from a different MCG. The consistency of our results to identify the MCG of a given S. rolfsii isolate using the combined sequences of EF1α and RPB2 genes was confirmed using blind trials. Our study demonstrates that sequence variation in the protein-coding genes EF1α and RPB2 may be exploited as a diagnostic tool for MCG typing in S. rolfsii as well as to identify previously undescribed MCGs.
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http://dx.doi.org/10.1094/PHYTO-07-12-0151-RDOI Listing
May 2013

Molecular and Pathogenic Characterization of Fusarium redolens, a New Causal Agent of Fusarium Yellows in Chickpea.

Plant Dis 2011 Jul;95(7):860-870

Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), 14080 Córdoba, Spain.

The association of Fusarium redolens with wilting-like symptoms in chickpea in Lebanon, Morocco, Pakistan, and Spain is reported for the first time, together with the molecular and pathogenic characterization of isolates of the pathogen from chickpea of diverse geographic origin. Maximum parsimony analysis of sequences of the translation elongation factor 1α (TEF-1α) gene grouped all F. redolens isolates from chickpea in the same main clade. Pathogenicity assays using three chickpea cultivars and isolates from different geographic origins indicated that F. redolens is mildly virulent on chickpea. Moreover, infection of chickpea by F. redolens induces a disease syndrome similar to that caused by the yellowing pathotype of F. oxysporum f. sp. ciceris, including leaf yellowing and necrosis that develop upward from the stem base, and premature senescence of the plant. In contrast, F. redolens does not cause discoloration of the vascular tissues in chickpea but does cause brown necrotic lesions in the tap root and necrosis of lateral roots. F. redolens is not easily differentiated from F. oxysporum f. sp. ciceris using morphology-based diagnosis, and the two species cause similar symptoms on chickpea; therefore, the use of molecular protocols should help to avoid misdiagnoses of Fusarium yellows in chickpea.
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http://dx.doi.org/10.1094/PDIS-12-10-0946DOI Listing
July 2011

Genetic structure of Xiphinema pachtaicum and X. index populations based on mitochondrial DNA variation.

Phytopathology 2011 Oct;101(10):1168-75

Instituto de Agricultura Sostenible, Cordoba, Spain.

The dagger nematodes Xiphinema pachtaicum and X. index are two of the most widespread and frequently occurring Xiphinema spp. co-infesting vineyards and other crops and natural habitats worldwide. Sexual reproduction is rare in these species. The primary objective of this study was to determine the genetic structure of X. pachtaicum and X. index populations using eight and seven populations, respectively, from different "wine of denomination of origin (D.O.) zones" in Spain and Sardinia (Italy), by studying mitochondrial (cytochrome oxidase c subunit 1 or COI) and nuclear (D2-D3 expansion segments of 28S rDNA) markers. Both Xiphinema spp. showed low intraspecific divergence among COI sequences, ranging from 0.2% (1 base substitution) to 2.3% (10 substitutions) in X. pachtaicum and from 0.2% (1 base substitution) to 0.4% (2 substitutions) in X. index. Population genetic structure was strong for both species. Nevertheless, molecular differences among grapevine-growing areas were not significant, and intrapopulation diversity was very low. It is hypothesized that this genetic homogeneity in the nematode populations reflects their predominant parthenogenetic reproduction mode and low dispersal abilities. Our results also show that X. pachtaicum populations in Spain have possibly been established from two different populations of origin. Results also demonstrated that the two DNA regions studied are suitable diagnostic markers for X. index and X. pachtaicum.
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http://dx.doi.org/10.1094/PHYTO-07-10-0194DOI Listing
October 2011