Differential elemental uptake in three pseudo-metallophyte C<Subscript>4</Subscript> grasses in situ in the eastern USA

Background and aims

Elemental uptake in serpentine floras in eastern North America is largely unknown. The objective of this study was to determine major and trace element concentrations in soil and leaves of three native pseudo-metallophyte C₄ grasses in situ at five sites with three very different soil types, including three serpentine sites, in eastern USA.

Methods

Pseudo-total and extractible concentrations of 15 elements were measured and correlated from the soils and leaves of three species at the five sites.

Results

Element concentrations in soils of pseudo-metallophytes varied up to five orders of magnitude. Soils from metalliferous sites exhibited higher concentrations of their characteristic elements than non-metalliferous. In metallicolous populations, elemental concentrations depended on the element. Concentrations of major elements (Ca, Mg, K) in leaves were lower than typical toxicity thresholds, whereas concentrations of Zn were higher.

Conclusions

In grasses, species can maintain relatively low metal concentrations in their leaves even when soil concentrations are richer. However, in highly Zn-contaminated soil, we found evidence of a threshold concentration above which Zn uptake increases drastically. Finally, absence of main characteristics of serpentine soil at one site indicated the importance of soil survey and restoration to maintain serpentinophytes communities and avoid soil encroachment.

     

Metal hyperaccumulating Brassicaceae from the ultramafic area of Yahyalı in Kayseri province,Turkey

Many of the plants found in serpentine areas are endemics and they may accumulate Ni at high concentration. High accumulation of Cr is rare, or in some views, never properly demonstrated. Generally, a very small proportion of any serpentine flora shows high accumulation of Ni, in some serpentine areas Ni accumulators are completely absent. There are approximately 570 hyperaccumulator plant species found on earth, 450 of them are Ni hyperaccumulators. A few of the Ni accumulators have potential for phytoremediation or phytomining. In the present study, 19 different Brassicaceae members growing in serpentine habitats in the district of Yahyal?, Kayseri province, Turkey viz., members of genera Aethionema, Alyssum, Arabis, Heldreichia, Hesperis, Iberis, Isatis, Microthlaspi, Odontarrhena, Pseudosempervivum and Thlaspi were investigated. Nickel concentrations in the soil and underground and aboveground parts of plants were determined by using ICP-OES. It was observed that Ni concentrations of seven taxa (Odontarrhena muralis, O. oxycarpa, Isatis cappadocica subsp. cappadocica, Microthlaspi perfoliatum, Pseudosempervivum sempervivum, Thlaspi triangulare, Thlaspi rosulare) reach the threshold criterion of 1,000 mg kg^?1 for Ni hyperaccumulation. In this study Ni concentrations in aboveground tissues of I. cappadocica subsp. cappadocica are determined as 5,587 mg kg^?1 (in dry weight). Accordingly, it is suggested that this taxon be added to the list of Ni hyperaccumulator plants.     

Dermatophytosis in Military in the Central-West Region of Brazil: Literature Review

Background

Dermatophytes represent a group of keratinophilic fungi capable of invading the superficial layer of the skin, hair, and nails of humans and animals. There is a high prevalence of dermatomycosis in tropical regions, and military personnel are susceptible to this kind of infection due to the type of occupational activities.

Objective

This study was to investigate dermatophytosis in military, in addition to predisposing factors to such infections.

Methods

The direct examination of the 221 samples obtained was conducted by preparing fresh slides, clarified with KOH. The clinical materials were seeded in duplicate in SDA and in Mycosel agar medium. The identification of the etiologic agents was performed according to the Riddell technique.

Results

99/221 (44.8 %) of the dermatophyte infection agents distributed in the three taxonomic genera that cause Tinea were recovered. The Trichophyton genus was the most representative and T. rubrum species 33 (33.3 %), the most prevalent. The other species found were as follows: T. tonsurans 13 (13.1 %), T. verrucosum 11 (11.1 %), T. interdigitale 9 (9.1 %), and T. mentagrophytes 6 (6.1 %). Among the most affected anatomical sites were skin 83 (83.8 %) and nails 17 (17.2 %).

Conclusions

Dermatophyte infections are common disorders in tropical countries. These infections lead to a variety of clinical manifestations. This study reports the incidence of dermatophytosis in the military personnel in the Central-West Region of Brazil. The occupational activities of the military individuals, in addition to the hot and humid climate of the region, can predispose them to infection by these fungal entities.     

Stable carbon and nitrogen isotope ratios of Eucalyptus and Acacia species along a seasonal rainfall gradient in Western Australia

Key message

Eucalyptus and Acacia species were surprisingly similar with respect to variations in δ ¹³ C, δ ¹⁵ N. Both genera respond with speciation and associated changes in leaf structure to drought.

Abstract

Stable carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) in leaves of eucalypts (Corymbia and Eucalyptus) and Acacia (and some additional Fabaceae) species were investigated together with specific leaf area (SLA), leaf nitrogen (N) and leaf phosphorous (P) concentration along a north–south transect through Western Australia covering winter- and summer-dominated rainfall between 100 and 1,200 mm annually. We investigated 62 eucalypts and 78 woody Fabaceae species, mainly of the genus Acacia. Leaf δ¹³C values of Eucalyptus and Acacia species generally increased linearly with latitude from ?29.5 ± 1.3 ‰ in the summer-dominated rainfall zone (15°S–18°S) to about ?25.7 ± 1.1 ‰ in the winter-dominated rainfall zone (29°S–31°S). δ¹⁵N increased initially with southern latitudes (0.5 ± 1.6 ‰ at 15°S; 5.8 ± 3.3 ‰ at 24–29°S) but decreased again further South (4.6 ± 3.5 ‰ at 31°S). The variation in δ¹³C and δ¹⁵N was probably due to speciation of Eucalyptus and Acacia into very local populations. There were no species that were distributed over the whole sampling area. The variation in leaf traits was larger between species than within species. Average nitrogen concentrations were 11.9 ± 1.05 mg g^?1 in Eucalyptus, and were 18.7 ± 4.1 mg g^?1 in Acacia. Even though the average nitrogen concentration was higher in Acacia than Eucalyptus, δ¹⁵N gave no clear indication for N₂ fixation in Acacia. In a multiple regression, latitude (as a surrogate for rainfall seasonality), mean rainfall, leaf nitrogen concentration, specific leaf area and nitrogen fixation were significant and explained 69 % of the variation of δ¹³C, but only 36 % of the variation of δ¹⁵N. Higher nitrogen and phosphorus concentration could give Acacia an advantage over Eucalyptus in arid regions of undefined rainfall seasonality.     

Biogenic ethylene promotes seedling emergence from the sediment seed bank in an ephemeral tropical rock pool habitat

Background and aims

Ethylene has been increasingly implicated as a regulatory mechanism in plant germination, growth, and development, and is produced from the sediments of freshwater habitats. In this paper, we analyse the production and origin of ethylene from ephemeral freshwater rock pool sediments, and explore the role of ethylene in regulating seedling emergence from the seed bank.

Methods

The production of ethylene from rock pool sediments subjected to variable moisture content and antibiotic treatments was assessed through gas chromatography, and the role of ethylene in regulating seedling emergence was determined by seedling emergence assays and seed germination experiments.

Results

Biogenic ethylene production from rock pool sediments occurred rapidly (3–6 h) following inundation, with the majority of seedling emergence occurring between 36 and 72 h. Inoculation of sediments with streptomycin and amphotericin B resulted in significantly reduced ethylene production (up to 60 % and 84 % respectively), and completely inhibited seedling emergence. Additionally, the exposure of dormant seeds to ethylene resulted in significantly increased seed germination percentage in five out of six rock pool species.

Conclusions

Biogenic ethylene production may play an important role in regulating seed dormancy and the timing of seedling emergence from the sediment seed bank following inundation events in rock pools and other freshwater aquatic communities.     

Candidaemia Observed at a University Hospital in Milan (Northern Italy) and Review of Published Studies from 2010 to 2014

Background

Candida species represent the fourth leading cause of nosocomial bloodstream infections (BSI) worldwide. However, candidaemia rates and species involved vary geographically.

Objectives

To evaluate the epidemiological pattern, risk factors for mortality and antifungal therapy of Candida BSI over a 5-year period (2008–2012) in a university hospital in northern Italy together with a review of the recent literature concerning candidaemia.

Methods

A retrospective cohort study cross-linked with microbiology database was performed.

Results

A total of 89 Candida BSI were identified in 42 males (47 %) and 47 females (52.8 %). The median age was 69 years (interquartile range 55–78) with 61.8 % of patients being older than 65 years. Considering all hospitalized patients, the overall incidence rate of candidaemia increased significantly from 2008 to 2012 (from 0.4 to 1.68 episodes per 10,000 patient/days) (p = 0.0001) with a mean linear increase in 5 new cases per year. Candida albicans was the predominant species isolated (64 %) followed by C. glabrata (19.1 %). The latter species was observed with significantly higher frequency in Internal Medicine and Intensive Care Units (ICU). In-hospital crude mortality was 41.6 %.

Conclusions

Candidaemia is an increasing BSI in our university hospital, in accordance with that observed in northern Italy, and it is still associated with high in-hospital crude mortality.     

Development of universal genetic markers based on single-copy orthologous (COSII) genes in Poaceae

Key message

We develop a set of universal genetic markers based on single-copy orthologous (COSII) genes in Poaceae.

Abstract

Being evolutionary conserved, single-copy orthologous (COSII) genes are particularly useful in comparative mapping and phylogenetic investigation among species. In this study, we identified 2,684 COSII genes based on five sequenced Poaceae genomes including rice, maize, sorghum, foxtail millet, and brachypodium, and then developed 1,072 COSII markers whose transferability and polymorphism among five bamboo species were further evaluated with 46 pairs of randomly selected primers. 91.3 % of the 46 primers obtained clear amplification in at least one bamboo species, and 65.2 % of them produced polymorphism in more than one species. We also used 42 of them to construct the phylogeny for the five bamboo species, and it might reflect more precise evolutionary relationship than the one based on the vegetative morphology. The results indicated a promising prospect of applying these markers to the investigation of genetic diversity and the classification of Poaceae. To ease and facilitate access of the information of common interest to readers, a web-based database of the COSII markers is provided (http://www.sicau.edu.cn/web/yms/PCOSWeb/PCOS.html).     

Overexpression of Sirtuin2 prevents high glucose-induced vascular endothelial cell injury by regulating the p53 and NF-κB signaling pathways

Objectives

To investigate the potential role and underlying mechanism of Sirtuin2 (SIRT2) in regulating high glucose (HG)-induced vascular endothelial cell injury by using human umbilical vein endothelial cells (HUVECs).

Results

SIRT2 mRNA and protein expression levels were decreased in HG-treated HUVECs. SIRT2 overexpression increased viability, decreased apoptosis and reduced levels of reactive oxygen species in HG-treated HUVECs. SIRT2 overexpression decreased TNF-α expression (146.5 ± 22.8 pg TNF-α ml^?1) relative to that in the empty vector group (263.5 ± 18.5 pg TNF-α ml^?1) and decreased MCP-1 expression (63.8 ± 9.85 pg MCP-1 ml^?1) relative to that in the empty vector group (105.8 ± 8.5 pg MCP-1 ml^?1). SIRT2 overexpression decreased the acetylation of p53 by 33% and decreased the acetylation of NF-κB p65 by 58% in HG-treated HUVECs.

Conclusion

SIRT2 prevents HG-induced vascular endothelial cell injury through suppressing the p53 and NF-κB signaling pathways.

     

Relationships between serpentine soils and vegetation in a xeric inner-Alpine environment

Aims

In serpentinitic areas non-endemic plants suffer from the serpentine syndrome, due to high Ni and Mg concentrations, low nutrients and Ca/Mg ratio. We evaluated the environment-soil-vegetation relationships in a xeric inner-alpine area (NW Italy), where the inhibited pedogenesis should enhance parent material influences on vegetation.

Methods

Site conditions, topsoil properties, plant associations and species on and off serpentinite were statistically associated (51 sites).

Results

Serpentine soils had higher Mg and Ni concentrations, but did not differ from non-serpentine ones in nutrient contents. The 15 vegetation clusters often showed substrate specificity. Two components of the Canonical Analysis of Principal Coordinates, respectively related to Mg and to Ni and heat load, identified serpentine vegetation. Random Forests showed that several species were positively correlated with Ni and/or Ca/Mg or Mg, some were negatively associated with high Ni, Mg excess affected only few species. Considering only serpentine sites, nutrients and microclimate were most important.

Conclusions

Ni excess most often precludes the presence of plant species on serpentinite, while an exclusion due to Mg is rarer. Endemic species are mostly adapted to both factors. Nutrient scarcity was not specific of serpentine soils in the considered environment. Considering only serpentine sites, nutrient and microclimatic gradients drove vegetation variability.     

Two new species of the <Emphasis Type="Italic">Fusarium solani</Emphasis> species complex isolated from compost and hibiscus (<Emphasis Type="Italic">Hibiscus</Emphasis> sp.)

Two new species in the Fusarium solani species complex (FSSC) are described and introduced. The new taxa are represented by German isolates CBS 142481 and CBS 142480 collected from commercial yard waste compost and vascular tissue of a wilting branch of hibiscus, respectively. The phylogenetic relationships of the collected strains to one another and within the FSSC were evaluated based on DNA sequences of 6 gene loci. Due to the limited sequence data available for reference strains in GenBank, however, a multi-gene phylogenetic analysis included partial sequences for the internal transcribed spacer region and intervening 5.8S nrRNA gene (ITS), translation elongation factor 1-alpha (tef1) and the RNA polymerase II second largest subunit (rpb2). Morphological and molecular phylogenetic data independently showed that these strains are distinct populations of the FSSC, nested within Clade 3. Thus, we introduce Fusarium stercicola and Fusarium witzenhausenense as novel species in the complex. In addition, 19 plant species of 7 legume genera were evaluated for their potential to host the newly described taxa. Eighteen plant species were successfully colonized, with 6 and 9 of these being symptomatic hosts for F. stercicola and F. witzenhausenense, respectively. As plants of the family Fabaceae are very distant to the originally sourced material from which the new taxa were recovered, our results suggest that F. stercicola and F. witzenhausenense are not host-specific and are ecologically fit to sustain stable populations in variety of habitats.     

Serpentine and polyploid differentiation withinGalium pumilum agg. (Rubiaceae) in Eastern C. Europe

The local differentiation of a model group,Galium pumilum agg., was studied in serpentine versus non-serpentine habitats in the Czech Republic and adjacent regions in Austria, Germany and Poland. Serpentine habitats form ecologically distinct islands within the landscape; local micro-evolutionary processes may be important there, both because of small population sizes and the strong selection effects of the metal-rich soils. TheGalium pumilum agg. is a group of taxa showing typical karyological and ecological differentiation; the following species and cytotypes were studied:Galium pumilum Murray (2n=8x=88),G. valdepilosum Heinr. Braun (2n=2x=22, 2n=4x=44),G. sudeticum Tausch (2n=4x=44) andG. austriacum Jacq. (2n=4x=44). The karyological and taxonomic investigation showed that serpentine versus non-serpentine habitats do not play an important role in the differentiation of the species studied. (1) The examined populations ofG. pumilum Murray were homogeneous in chromosome numbers, belonging to the octoploid (2n=88) cytotype only. (2)G. valdepilosum consists of two cytotypes. Both of them occur on and off serpentine sites, but they show pronounced East-West distributional difference. (3)G. sudeticum occupies special localities on serpentine in western Bohemia, which are geographically isolated from its nearest localities in the Krkono?e Mts. The plants coming from both localities belong to the tetraploid cytotype. (4) A highly polyploid plant (2n=12x=ca. 132) from theG. pumilum group was found on serpentine. From the methodological point of view, pollen size turned out to be reliable only for distinguishing octoploids from diploids and tetraploids, but it is less suitable for separating the latter two ploidy levels. The occurrence ofG. austriacum is reported for the Czech Republic for the first time with certainty. This record extends the known distribution area ofG. austriacum in the NW direction.     

Effects of substrate type, moisture and its interactions on soil seed survival of three Rumex species

Background and Aims

Seed bank persistence plays a highly relevant role for population dynamics. The impact of interacting environmental factors on seed longevity has only scarcely been investigated. We aimed to analyse the effects of varied soil substrate type and moisture on soil seed survival.

Methods

Seeds of three Rumex species native to different habitats were buried in pots placed in open-air basins. The factors substrate (sand, loam, mud), water table depth (WTD; high, intermediate, low), time, and their interactions were investigated. Viability was tested after 6, 12, and 18 months.

Results

Seeds of R. acetosella (dry habitat) were short-term persistent with highest survival in low WTD on sand. Survival in R. acetosa (moist habitat) was very strongly reduced after 6 months with highest survival under wet conditions. R. maritimus (wet habitat) had overall long-term seed survival, where ‘substrate type’ had the strongest impact. Significant interactions of ‘substrate type’ and WTD were detected.

Conclusions

Seed bank longevity is not a fixed species trait, but varies with environmental factors. Soil moisture, substrate type and their interactions have different effects on the studied species. Persistence-classifications ought to consider the impact of environmental factors.     

Folk knowledge of invertebrates in Central Europe - folk taxonomy,nomenclature, medicinal and other uses,folklore, and nature conservation

Background

There is scarce information about European folk knowledge of wild invertebrate fauna. We have documented such folk knowledge in three regions, in Romania, Slovakia and Croatia. We provide a list of folk taxa, and discuss folk biological classification and nomenclature, salient features, uses, related proverbs and sayings, and conservation.

Methods

We collected data among Hungarian-speaking people practising small-scale, traditional agriculture. We studied “all” invertebrate species (species groups) potentially occurring in the vicinity of the settlements. We used photos, held semi-structured interviews, and conducted picture sorting.

Results

We documented 208 invertebrate folk taxa. Many species were known which have, to our knowledge, no economic significance. 36 % of the species were known to at least half of the informants. Knowledge reliability was high, although informants were sometimes prone to exaggeration. 93 % of folk taxa had their own individual names, and 90 % of the taxa were embedded in the folk taxonomy.Twenty four species were of direct use to humans (4 medicinal, 5 consumed, 11 as bait, 2 as playthings). Completely new was the discovery that the honey stomachs of black-coloured carpenter bees (Xylocopa violacea, X. valga) were consumed. 30 taxa were associated with a proverb or used for weather forecasting, or predicting harvests. Conscious ideas about conserving invertebrates only occurred with a few taxa, but informants would generally refrain from harming firebugs (Pyrrhocoris apterus), field crickets (Gryllus campestris) and most butterflies. We did not find any mythical creatures among invertebrate folk taxa. Almost every invertebrate species was regarded as basically harmful. Where possible, they were destroyed or at least regarded as worth eradicating. However, we could find no evidence to suggest any invertebrate species had suffered population loss as a result of conscious destruction. Sometimes knowledge pertaining to the taxa could have more general relevance, and be regarded as folk wisdom concerning the functioning of nature as a whole.

Conclusions

The high number of known invertebrate folk taxa suggests that it would be worth conducting further investigations in other areas of Europe.

     

Development of a wheat single gene FISH map for analyzing homoeologous relationship and chromosomal rearrangements within the Triticeae

Key message

A cytogenetic map of wheat was constructed using FISH with cDNA probes. FISH markers detected homoeology and chromosomal rearrangements of wild relatives, an important source of genes for wheat improvement.

Abstract

To transfer agronomically important genes from wild relatives to bread wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) by induced homoeologous recombination, it is important to know the chromosomal relationships of the species involved. Fluorescence in situ hybridization (FISH) can be used to study chromosome structure. The genomes of allohexaploid bread wheat and other species from the Triticeae tribe are colinear to some extent, i.e., composed of homoeoloci at similar positions along the chromosomes, and with genic regions being highly conserved. To develop cytogenetic markers specific for genic regions of wheat homoeologs, we selected more than 60 full-length wheat cDNAs using BLAST against mapped expressed sequence tags and used them as FISH probes. Most probes produced signals on all three homoeologous chromosomes at the expected positions. We developed a wheat physical map with several cDNA markers located on each of the 14 homoeologous chromosome arms. The FISH markers confirmed chromosome rearrangements within wheat genomes and were successfully used to study chromosome structure and homoeology in wild Triticeae species. FISH analysis detected 1U-6U chromosome translocation in the genome of Aegilops umbellulata, showed colinearity between chromosome A of Ae. caudata and group-1 wheat chromosomes, and between chromosome arm 7S#3L of Thinopyrum intermedium and the long arm of the group-7 wheat chromosomes.     

Usefulness of 1,3 Beta-<Emphasis Type="SmallCaps">d</Emphasis>-Glucan Detection in non-HIV Immunocompromised Mechanical Ventilated Critically Ill Patients with ARDS and Suspected <Emphasis Type="Italic">Pneumocystis jirovecii</Emphasis> Pneumonia

Introduction

Pneumocystis jirovecii pneumonia (PCP) is a major cause of disease in immunocompromised individuals. Diagnosis is typically obtained by microscopy and/or PCR. For ambiguous PCR results, we evaluated the new biomarker 1,3-Beta-d-Glucan (BDG).

Methods

BDG serum levels were assessed and correlated to PCR results in immunosuppressed patients with ARDS.

Results

11 (22%) out of 50 patients had suspected PCP. APACHE II (26 vs. 24; p < 0.002), SOFA score (16 vs. 14; p < 0.010) and mortality rate (34 vs. 69% p < 0.004; 34 vs. 80% p < 0.003) were significantly altered in patients with positive (pPCR) and slightly positive (spPCR) PCJ PCR as compared to patients with no-PCP (nPCP). BDG levels were significantly lower in patients with nPCP (86; 30–315 pg/ml) than in patients with pPCR (589; 356–1000 pg/ml; p < 0.001) and spPCP (398; 297–516 pg/ml; p < 0.004) referring to the cutoff in this study for PCP of 275 pg/ml. An overall sensitivity (S) of 92% (95% CI 86–96%) and specificity (SP) of 84% (95% CI 79–85%) for PCP were found for the BDG Fungitell assay. In detail, S of 98% (95% CI 94–100%) and SP of 86% (95% CI 82–92%) for pPCP and S of 98% (95% CI 96–100%) and SP of 88% (95% CI 86–96%) for spPCO were found.

Conclusion

Serum BDG levels were strongly elevated in PCP, and the negative predictive value is high. BDG could be used as a preliminary test for patients with suspected PCP, especially in patients with slightly positive PCR results.

     

Nitric Oxide Donors Augment Interleukin-1β-Induced Vascular Endothelial Growth Factor in Airway Smooth Muscle Cells

Angiogenesis and microvascular leakage are features of chronic inflammatory diseases of which molecular mechanisms are poorly understood. We investigated the effects of interleukin-1β (IL-1β) on the expression and secretion of vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in porcine airway smooth muscle cells (PASMC) in relation to a nitric oxide (NO) pathway. Serum-deprived (48 h) PASMC were stimulated with IL-1β alone or with NO donor, l-arginine and/or NO synthase inhibitor l-NAME for 4 and 24 h. IL-1β did not affect PlGF release, but augmented VEGF release (2.4-fold) after 24 h. VEGF release was inhibited by l-NAME (531.8 ± 52 pg/ml), but restored and further elevated by l-arginine (1,529 ± 287 pg/ml). IL-1β up-regulated VEGF mRNA (1.8-fold) and this response was attenuated by l-NAME (1.1-fold) and augmented by l-arginine (3.8-fold) at 4 h. Restoration of a NO pathway by l-arginine in l-NAME-treated cells resulted in elevated VEGF mRNA levels (2.2-fold). [³H]Thymidine incorporation assay revealed enhanced porcine pulmonary artery endothelial cell proliferation in response to IL-1β, VEGF and PlGF, and this mitogenic effect was not influenced via the NO pathway. Our results suggest that a NO pathway modulates VEGF synthesis during inflammation contributing to bronchial angiogenesis and vascular leakage.     

Root distribution of different mature tree species growing on contrasting textured soils in temperate windbreaks

Aim

We studied the vertical and lateral root distribution of tree species from three genera (Populus spp. - poplar, Picea spp. - spruce, Salix spp. - willow) that were planted in temperate windbreaks and assessed the effects of soil texture on root density.

Methods

Root distribution to depths of up to 1 m was assessed using the trench-profile method at different distances from the tree rows (2, 6 and 9 m) in 18 mature (average age, 25 years-old) windbreak-sites that were located on light- or heavy-textured agricultural soils in southeastern Québec, Canada. Roots were classified into three diameter classes: fine (<1 mm), medium-size (1–5 mm), and coarse (>5 mm).

Results

Tree fine-root density in poplar and willow windbreaks was higher than in spruce windbreaks at 2 m from the tree row. Root densities were higher in light compared to heavy soils, but these differences were specific to poplar and spruce. Across species groups and soil types, 67 % of the roots occurred in the uppermost 30 cm. In this soil zone, different soil fertility variables (pH, clay content, CEC) were negatively correlated with root density. Densities of spruce and willow roots at 6 m from the tree row were much lower (and often unobserved) than that of poplar. At 9 m, low root densities were observed at only two sites.

Conclusions

We conclude that tree identity and soil type are important drivers of root distribution in temperate agroforestry systems. These results may have important implications for the management of tree competition in agroforestry systems and several ecosystem services that are provided by roots, including C-sequestration, erosion control and water infiltration.     

Partitioning of belowground C in young sugar maple forest

Background and aims

Trees allocate a high proportion of assimilated carbon belowground, but the partitioning of that C among ecosystem components is poorly understood thereby limiting our ability to predict responses of forest C dynamics to global change drivers.

Methods

We labeled sugar maple saplings in natural forest with a pulse of photosynthetic ¹³C in late summer and traced the pulse over the following 3 years. We quantified the fate of belowground carbon by measuring ¹³C enrichment of roots, rhizosphere soil, soil respiration, soil aggregates and microbial biomass.

Results

The pulse of ¹³C contributed strongly to root and rhizosphere respiration for over a year, and respiration comprised about 75 % of total belowground C allocation (TBCA) in the first year. We estimate that rhizosphere carbon flux (RCF) during the dormant season comprises at least 6 % of TBCA. After 3 years, 3.8 % of the C allocated belowground was recovered in soil organic matter, mostly in water-stable aggregates.

Conclusions

A pulse of carbon allocated belowground in temperate forest supplies root respiration, root growth and RCF throughout the following year and a small proportion becomes stabilized in soil aggregates.     

Population structure and association mapping of yield contributing agronomic traits in foxtail millet

Key message

Association analyses accounting for population structure and relative kinship identified eight SSR markers ( p < 0.01) showing significant association ( R ²  = 18 %) with nine agronomic traits in foxtail millet.

Abstract

Association mapping is an efficient tool for identifying genes regulating complex traits. Although association mapping using genomic simple sequence repeat (SSR) markers has been successfully demonstrated in many agronomically important crops, very few reports are available on marker-trait association analysis in foxtail millet. In the present study, 184 foxtail millet accessions from diverse geographical locations were genotyped using 50 SSR markers representing the nine chromosomes of foxtail millet. The genetic diversity within these accessions was examined using a genetic distance-based and a general model-based clustering method. The model-based analysis using 50 SSR markers identified an underlying population structure comprising five sub-populations which corresponded well with distance-based groupings. The phenotyping of plants was carried out in the field for three consecutive years for 20 yield contributing agronomic traits. The linkage disequilibrium analysis considering population structure and relative kinship identified eight SSR markers (p < 0.01) on different chromosomes showing significant association (R ² = 18 %) with nine agronomic traits. Four of these markers were associated with multiple traits. The integration of genetic and physical map information of eight SSR markers with their functional annotation revealed strong association of two markers encoding for phospholipid acyltransferase and ubiquitin carboxyl-terminal hydrolase located on the same chromosome (5) with flag leaf width and grain yield, respectively. Our findings on association mapping is the first report on Indian foxtail millet germplasm and this could be effectively applied in foxtail millet breeding to further uncover marker-trait associations with a large number of markers.