Effect of forest management on plant species diversity in Castanea sativa stands in Salamanca (Spain) and the Cévennes (France).

For the last centuries, marked land use changes have taken place throughout the Mediterranean region. These changes have a great impact on plant diversity, variations of which can affect in return ecosystem functioning. This is particularly true for sweet chestnut (Castanea sativa Mill.) stands (groves or coppices) that have been more or less abandoned since the end of the last century. Thus, our objective was to analyse the consequences of various management types on plant species diversity, or to analyse if the land use changes may affect the diversity of plant species in chestnut areas of Southern Europe: in chestnut stands of the Honfría forest, located in the South of Salamanca province in Spain, and in the Cévennes in Southern France. Results indicate that plant species diversity is higher in groves than in coppice stands. Cultivated groves were generally characterized by small heliophilous therophytes, and abandoned groves by hemicryptophytes with anemochorous dispersal mode and chamaephytes. Coppice stands were characterized more particularly by phanerophytes with zoochorous dispersal mode. Thus, plant species diversity differs according to management types. The 17% of common species were found between the two Mediterranean areas studied. This difference can be explained by different ecological conditions (elevation, soil type), different management types (grove, coppice stand), and different stand characteristics (shoot density, diameter at breast height). The cultivated grove plots were very different from the other stands that constituted one sub-group. In the Honfría forest, the values of Jaccard index indicated that the cultivated grove had a plant species composition very different from the other stands. In the Cévennes, the lowest values of the Jaccard index were also found between the cultivated grove and the other stands. One solution could be to maintain a landscape mosaic constituted of diverse chestnut stands modified by human activities (chestnut groves, abandoned chestnut groves and chestnut coppice stands). This could allow the enhancement of the high regional plant diversity.We thank the European Union (MANCHEST QLK5-CT- 2001 – 00029 z contracts, DG XII, for financial support).Peer reviewe

Biotecnología microbiana para la agricultura en Producción Integrada: Buscando nuevos biofertilizantes para patata

Póster presentado en la Feria del Sector Agropecuario Salamaq 14N

Mesorhizobium olivaresii sp. nov. isolated from Lotus corniculatus nodules

16 páginas, 3 figuras, 2 tablas. -- The definitive version is available at http://www.elsevier.comIn this study four Mesorhizobium strains isolated from Lotus corniculatus nodules in Granada (Spain) were characterized. Their 16S rRNA gene sequences were closely related to those of M. albiziae LMG 23507T and M. chacoense Pr5T showing 99.4 and 99.2% similarity values, respectively. The analysis of concatenated rpoB, recA, atpD and glnII genes showed they formed a cluster with internal similarities higher than 97%. The closest species also were M. albiziae LMG 23507T and M. chacoense Pr5T showing similarity values lower than 92% in rpoB, recA and glnII genes and lower than 96.5% in the atpD gene. These results indicated that the L. corniculatus strains belong to a new species of genus Mesorhizobium which was confirmed by DNA-DNA hybridization and phenotypic characterization. Therefore a new species with the name Mesorhizobium olivaresii sp. nov. is proposed, and the type strain is CPS13T (LMG 29295T = CECT 9099T).This work was supported by the EU-INCO project LOTASSA (J.S.) and Junta de Andalucía (Spain). JDFF is recipient of a predoctoral fellowship from Universidad de Salamanca.Peer reviewe

Rhizosphere mycobiome diversity in four declining Mediterranean tree species

IntroductionForests in the Mediterranean basin are currently in decline. Their resilience has been eroded as a result of climate change and anthropogenic impacts, making them vulnerable to increasingly frequent episodes of drought, fire and the spread of pests and diseases. The impact of these natural and anthropogenic events on soil biodiversity is of particular concern, as the soil fungal community plays a key role in ecosystem homeostasis.Objectives and methodsIn order to analyse the relationship between soil health status and fungal diversity, soil samples were collected from declining Mediterranean forests of Castanea sativa (chestnut), Quercus ilex (holm oak), Quercus suber (cork oak) and Quercus pyrenaica (Pyrenean oak). A metabarcoding study was carried out by sequencing the ITS genomic region.ResultsA total of 674 fungal genera were found. It has not been possible to explain the differences in health status from the fungal genera found exclusively on declining forest soils, as none of them have been described as pathogenic. Healthy chestnut soils were characterized by a high alpha diversity and a higher abundance of the genus Metarhizium. No differentially abundant genera were found in any of the other forest species tested. Declining chestnut soils harbored more abundance of ectomycorrhizae and soil saprotrophs than healthy samples. Ectomycorrhizae were the dominant lifestyle in all oak species regardless of health status, whereas arbuscular mycorrhizae were preferentially found in declining cork oak soils.DiscussionThis work highlights the resilience of fungal communities of soil against decline and highlights the need to further investigate its relationship with the forest’s ability to cope with the challenges of climate change

Pseudomonas helmanticensis sp. nov., isolated from a forest soil

18 páginas, 2 figuras, 2 tablas. – The definitive versión is available at http://ijs.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.063560-0 -- MHRB is recipient of a JAE-Doc researcher contract from CSIC cofinanced by ERDF. MJC, JDFF and RM are recipients of contracts supported by this projectA bacterial strain named OHA11T was isolated in the course of a study of phosphate solubilizing bacteria occurring in a forest soil from Salamanca, Spain. The 16S rRNA gene sequence had 99.1% identity with respect to the closest relative Pseudomonas baetica a390T, and the following closest related species with 98.9 % similarity were P. jessenii, P. moorei, P. umsongensis, P. mohnii and P. koreensis, for which OHA11T was classified within genus Pseudomonas. The analysis of housekeeping genes rpoB, rpoD and gyrB confirmed its phylogenetic affiliation and showed identities lower than 95% in almost all cases with respect to the mentioned closest relatives. The strain has two polar flagella. The respiratory quinone is Q9. The major fatty acids are 16:0, 18:1 ω7c and 16:1 ω7c/ 15:0 iso 2OH in summed feature 3. The strain is oxidase, catalase and urease positive, the arginine dihydrolase system is present but nitrate reduction, β–galactosidase production and esculine hydrolysis are negative. It can grow at 31ºC and at pH 11. The DNA G+C content was 58.1 mol %. DNA-DNA hybridization results showed values lower than 49% relatedness with respect to the type strains of the seven closest related species. Therefore, the combined results of genotypic, phenotypic and chemotaxonomic data support the classification of strain OHA11 into a novel species of Pseudomonas, for which the name P. helmanticensis sp. nov. is proposed. The type strain is OHA11T (=LMG 28168T, CECT 8548T).This research was funded by MINECO (Spanish Central Government) Grant INNPACTO IPT-2011-1283-060000.Peer reviewe

Rhizobium Promotes Non-Legumes Growth and Quality in Several Production Steps: Towards a Biofertilization of Edible Raw Vegetables Healthy for Humans

The biofertilization of crops with plant-growth-promoting microorganisms is currently considered as a healthy alternative to chemical fertilization. However, only microorganisms safe for humans can be used as biofertilizers, particularly in vegetables that are raw consumed, in order to avoid sanitary problems derived from the presence of pathogenic bacteria in the final products. In the present work we showed that Rhizobium strains colonize the roots of tomato and pepper plants promoting their growth in different production stages increasing yield and quality of seedlings and fruits. Our results confirmed those obtained in cereals and alimentary oil producing plants extending the number of non-legumes susceptible to be biofertilized with rhizobia to those whose fruits are raw consumed. This is a relevant conclusion since safety of rhizobia for human health has been demonstrated after several decades of legume inoculation ensuring that they are optimal bacteria for biofertilization

Historia de la investigación en la simbiosis leguminosa-bacteria: una perspectiva didáctica

After cereals, legumes constitute the second most important family of crops for human and animal consumption. However, in contrast to the former, legumes are capable of growing in arid soils of low fertility, due to their ability to establish symbiotic associations with soil bacteria called rhizobia. These microorganisms form special organs in the roots of legumes called nodules, where atmospheric dinitrogen (N₂) is transformed into ammonium that is exported to the plant for growth. Since their discovery in legume nodules until today, knowledge of the bacteria capable of establishing symbiosis with these plants has advanced in many aspects. Especially, advances in molecular techniques for bacterial identification and access to unexplored places have confirmed that the interaction of legumes with rhizobia is older, and that N₂-fixing bacteria are more abundant and diverse, than considered previously. Here, we attempt to relate the history of an association whose development is key in the history of mankind as we know it now.<br><br>Después de los cereales, las leguminosas constituyen la segunda familia en importancia para la alimentación humana y animal. Sin embargo, en contraste con ellos, las leguminosas son capaces de crecer en suelos áridos, de escasa fertilidad, lo que se debe a su capacidad para establecer asociaciones simbióticas con bacterias del suelo llamadas rhizobia. Estos microorganismos forman unos órganos especiales en las raíces de las leguminosas, los nódulos, donde el dinitrógeno (N₂) atmosférico se transforma en amonio que se exporta a la planta para su crecimiento. Desde su descubrimiento en los nódulos de las leguminosas hasta nuestros días, el conocimiento de las bacterias capaces de establecer simbiosis con estas plantas ha avanzado en múltiples aspectos. Sobre todo, los avances en las técnicas moleculares de identificación bacteriana y el acceso a lugares inexplorados ha permitido confirmar que la interacción de las leguminosas con los rhizobia es más antigua de lo que se creía y que las bacterias fijadoras de dinitrógeno (N₂) son más abundantes y diversas de lo que se había pensado. Trataremos de describir la historia de una asociación cuyo desarrollo ha sido, y es, clave en la historia de la humanidad tal como la conocemos ahora

Defining the Rhizobium leguminosarum Species Complex

Bacteria currently included in Rhizobium leguminosarum are too diverse to be considered a single species, so we can refer to this as a species complex (the Rlc). We have found 429 publicly available genome sequences that fall within the Rlc and these show that the Rlc is a distinct entity, well separated from other species in the genus. Its sister taxon is R. anhuiense. We constructed a phylogeny based on concatenated sequences of 120 universal (core) genes, and calculated pairwise average nucleotide identity (ANI) between all genomes. From these analyses, we concluded that the Rlc includes 18 distinct genospecies, plus 7 unique strains that are not placed in these genospecies. Each genospecies is separated by a distinct gap in ANI values, usually at approximately 96% ANI, implying that it is a ‘natural’ unit. Five of the genospecies include the type strains of named species: R. laguerreae, R. sophorae, R. ruizarguesonis, “R. indicum” and R. leguminosarum itself. The 16S ribosomal RNA sequence is remarkably diverse within the Rlc, but does not distinguish the genospecies. Partial sequences of housekeeping genes, which have frequently been used to characterize isolate collections, can mostly be assigned unambiguously to a genospecies, but alleles within a genospecies do not always form a clade, so single genes are not a reliable guide to the true phylogeny of the strains. We conclude that access to a large number of genome sequences is a powerful tool for characterizing the diversity of bacteria, and that taxonomic conclusions should be based on all available genome sequences, not just those of type strains

Linee guida di buone pratiche per l'identificazione ed il controllo di alcune malattie comuni dei boschi mediterranei

55 páginas, 54 figurasNell’attuale contesto di cambiamento climatico che stiamo vivendo da alcuni anni, le foreste mediterranee sono minacciate da un’ampia varietà di fattori di stress di origine biotica e abiotica. Periodi di siccità prolungata, temperature elevate e incendi boschivi stanno diventando sempre più frequenti nelle nostre foreste. Questi fattori di rischio abiotico sono stati accentuati a causa dell’abbandono rurale, poiché lo spopolamento porta a una diminuzione della pratica della selvicoltura tradizionale che storicamente ha contribuito a mitigare il rischio di incendi e altre minacce per la foresta. Le nostre foreste sono inoltre soggette ad agenti di stress di origine biotica: parassiti e patogeni in grado di indebolire e persino distruggere le masse forestali, che, se colpite dall’azione di insetti e/o microrganismi patogeni, sono più suscettibili a loro volta ad ulteriori elementi di stress. La combinazione di questi elementi nocivi, mette in pericolo la salute e l’esistenza dell’intero ecosistema forestale. Il progetto LIFE MycoRestore nasce con l’obiettivo di implementare diverse strategie per ottenere una gestione sostenibile delle foreste mediterranee e delle loro risorse. A tal fine, vengono utilizzate varie risorse micologiche innovative e pratiche di gestione forestale che consentono un migliore risultato economico, contribuendo nel contempo ad aumentare la resilienza e l’adattamento ai cambiamenti climatici delle foreste mediterranee in Spagna, Italia e Portogallo.LIFE MYCORESTORE. Innovative use of mycological resources for resilient and productive Mediterranean forests threatened by climate change (LIFE18 CCA/ES/1110)Peer reviewe

Defining the Rhizobium leguminosarum Species Complex

Bacteria currently included in Rhizobium leguminosarum are too diverse to be considered a single species, so we can refer to this as a species complex (the Rlc). We have found 429 publicly available genome sequences that fall within the Rlc and these show that the Rlc is a distinct entity, well separated from other species in the genus. Its sister taxon is R. anhuiense. We constructed a phylogeny based on concatenated sequences of 120 universal (core) genes, and calculated pairwise average nucleotide identity (ANI) between all genomes. From these analyses, we concluded that the Rlc includes 18 distinct genospecies, plus 7 unique strains that are not placed in these genospecies. Each genospecies is separated by a distinct gap in ANI values, usually at approximately 96% ANI, implying that it is a ‘natural’ unit. Five of the genospecies include the type strains of named species: R. laguerreae, R. sophorae, R. ruizarguesonis, “R. indicum” and R. leguminosarum itself. The 16S ribosomal RNA sequence is remarkably diverse within the Rlc, but does not distinguish the genospecies. Partial sequences of housekeeping genes, which have frequently been used to characterize isolate collections, can mostly be assigned unambiguously to a genospecies, but alleles within a genospecies do not always form a clade, so single genes are not a reliable guide to the true phylogeny of the strains. We conclude that access to a large number of genome sequences is a powerful tool for characterizing the diversity of bacteria, and that taxonomic conclusions should be based on all available genome sequences, not just those of type strains