Effects of elevated CO2, water stress, and inoculation with Glomus intraradices or Pseudomonas mendocina on lettuce dry matter and rhizosphere microbial and functional diversity under growth chamber conditions

Purpose  

In this study, we investigated the effects of elevated atmospheric CO₂, drought, and inoculation with a plant-growth-promoting rhizobacterium (PGPR) or an arbuscular mycorrhizal (AM) fungus on microbial community composition and functional diversity in the rhizosphere of Lactuca sativa L. cv. Tafalla.     

Diversity of the calabash tree (<Emphasis Type="Italic">Crescentia cujete</Emphasis> L.) in Colombia

Germplasm of the calabash tree (Crescentia cujete L.) was collected in five major regions of Colombia, i.e. the Andes, Caribbean, Amazon, Orinoco, and Pacific regions. Collecting this multipurpose tree was guided by the indigenous knowledge of farmers and artisans in each region. Large variation in fruit shapes and sizes was found, of which some forms were typical for certain regions. Overall 56 accessions were collected and roughly classified into 22 types by eight fruit shapes and eight sizes. Molecular markers (Amplified fragment length polymorphisms) were applied to leaf tip tissue originating from vegetatively propagated plants in order to assess the diversity available in the germplasm collected as well as to detect patterns of geographical or morphological similarity. One accession each of C. alata H.B.&K. and C. amazonica Ducke were used as outgroups. Overall, genetic diversity was high (mean Nei and Li’s coefficient of 0.43). No relations could be established between either geographical provenance or fruit morphology and patterns of genetic diversity. Concerning the outgroups, the C. amazonica accession appeared to be a distinct species. The C. alata accession, however, did not seem to be sufficiently distinct from C. cujete to merit species status. The latter material may in fact be a hybrid or serve to challenge the validity of interspecific organization of the genus Crescentia.

Ranking temperate woody species along a gradient of browsing by deer

As a result of diverse management policies, densities of red and roe deer have varied considerably for the last few decades in Europe. Their selective browsing on woody species can modify the interactions between competing species and thus change overall patterns of plant diversity in forests. However, no classification of woody species according to browsing by deer yet exists in Europe. The selectivity index, which measures the balance between availability and consumption of plant species by herbivores, could be used for such a classification. The aim of this study was, first, to rank woody species according to this selectivity index, then to test whether their rank changed when browsing pressure varied in space or time. We also explored morphological and ecological life traits (Ellenberg indicator values) that might explain differences in selectivity.In 2006, we re-sampled a network of 217 coupled floristic and browsing survey plots, which had been previously described twice (1976, 1981). The plots were located in the forest of Arc-en-Barrois (France), a large woodland area divided into a North and a South Forest which have had different histories of browsing pressure.For the three samples and the two forests, we calculated a selectivity index for 19 woody species. Dogwood (Cornus sp.) and field rose (Rosa arvensis) appeared to be the most selected species whereas beech (Fagus sylvatica), common mezereon (Daphne mezereum) and wild-service tree (Sorbus torminalis) were always avoided. The rank order of species according to their selectivity index remained stable over the three sample years and between the two forests (Spearman's rank correlations: ρ ≈ 0.8 spatially, and range from 0.3 to 0.8 temporally). This indicates that variations in browsing pressure did not strongly modify deer selectivity patterns. Selectivity was positively correlated with wood density and negatively correlated with maximum height of the species, but unrelated to other plant traits. Finally, selectivity can be seen as an intrinsic characteristic of those woody species, and could be used as an additional life trait when analyzing vegetation communities.     

Biomass burning in Brazil's Amazonian “arc of deforestation”: Burning efficiency and charcoal formation in a fire after mechanized clearing at Feliz Natal, Mato Grosso

Estimates of greenhouse-gas emissions from deforestation are highly uncertain because of high variability in key parameters and because of the limited number of studies providing field measurements of these parameters. One such parameter is burning efficiency, which determines how much of the original forest's aboveground carbon stock will be released in the burn, as well as how much will later be released by decay and how much will remain as charcoal. In this paper we examined the fate of biomass from a semideciduous tropical forest in the “arc of deforestation,” where clearing activity is concentrated along the southern edge of the Amazon forest. We estimated carbon content, charcoal formation and burning efficiency by direct measurements (cutting and weighing) and by line-intersect sampling (LIS) done along the axis of each plot before and after burning of felled vegetation. The total aboveground dry biomass found here (219.3 Mg ha⁻¹) is lower than the values found in studies that have been done in other parts of the Amazon region. Values for burning efficiency (65%) and charcoal formation (6.0%, or 5.98 Mg C ha⁻¹) were much higher than those found in past studies in tropical areas. The percentage of trunk biomass lost in burning (49%) was substantially higher than has been found in previous studies. This difference may be explained by the concentration of more stems in the smaller diameter classes and the low humidity of the fuel (the dry season was unusually long in 2007, the year of the burn). This study provides the first measurements of forest burning parameters for a group of forest types that is now undergoing rapid deforestation. The burning parameters estimated here indicate substantially higher burning efficiency than has been found in other Amazonian forest types. Quantification of burning efficiency is critical to estimates of trace-gas emissions from deforestation.     

Myoblast cell interaction with polydopamine coated liposomes

Liposomes are widely used, from biosensing to drug delivery. Their coating with polymers for stability and functionalization purposes further broadens their set of relevant properties. Poly(dopamine) (PDA), a eumelanin-like material deposited via the "self"-oxidative polymerization of dopamine at mildly basic pH, has attracted considerable interest in the past few years due to its simplicity, flexibility yet fascinating properties. Herein, we characterize the coating of different types of liposomes with PDA depending on the presence of oleoyldopamine in the lipid bilayer and the dopamine hydrochloride concentration. Further, the interaction of these coated liposomes in comparison to their uncoated counterparts with myoblast cells is assessed. Their uptake/association efficiency with these cells is determined. Further, their dose-dependent cytotoxicity with and without entrapped hydrophobic cargo (thiocoraline) is characterized. Taken together, the reported results demonstrate the potential of PDA coated liposomes as a tool in biomedical applications.     

Polyphasic characterization of Xanthomonas axonopodis pv. allii associated with outbreaks of bacterial blight on three Allium species in the Mascarene archipelago

Based on the number of new reports during the last two decades, bacterial blight of onion (Allium cepa) is considered an emerging disease. The causal agent, Xanthomonas axonopodis pv. allii, is pathogenic to several Allium species after inoculation, but outbreaks worldwide have been primarily reported on onion. We describe a unique epidemiological situation in Réunion Island, France, with concomitant outbreaks on three Allium species, onion, leek (A. porrum), and garlic (A. sativum). There was no host specialization within Allium spp. among strains associated with the three host species. Based on amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism, strains associated with these outbreaks in Réunion Island were highly related genetically to strains isolated from diseased plant samples and contaminated seed lots in the neighboring island of Mauritius, where the disease has occurred since 1984. All AFLP haplotypes were identified as X. axonopodis pv. allii based on polymerase chain reaction analysis using specific primers, biochemical tests, and/or pathogenicity tests. Two genetically related groups of strains (A and B) that can be distinguished by AFLP, differential utilization of three carbon sources, and xanthomonadin pigment production were detected initially after establishment of the pathogen. In less than 10 years after the establishment of the pathogen there was nearly an extinction of group A strains in Réunion Island, suggesting differences in fitness between strains in the two groups.     

PESO: a modelling framework to help improve management strategies for epidemics – application to sharka

The optimization of management strategies for plant diseases is a difficult task because of the complexity and variability of epidemic dynamics. Thanks to their ability to numerically simulate many scenarios, models can be used to estimate epidemiological parameters, assess the effectiveness of different management strategies and optimize them. This article presents the PESO (parameter estimation–simulation–optimization) modelling framework to help improve plant disease management strategies. This framework is based on (i) the characterization of the epidemic dynamics to estimate key epidemiological parameters, (ii) the use of spatially explicit models to simulate epidemic dynamics and disease management, and (iii) the use of numerical optimization methods to identify better management strategies. This approach is generic and can be applied to many diseases. The work presented here focuses on sharka (caused by Plum pox virus), which has a worldwide impact on the Prunus industry, and is associated with huge disease management costs in many countries, especially in France.     

Evaluation of PCR assays for the detection of Campylobacter fetus in bovine preputial scrapings and the identification of subspecies in South African field isolates

As a result of the high lability and slow growth of Campylobacter fetus subspecies, the laboratory diagnosis of bovine genital campylobacteriosis has always been difficult. This is especially true under South African conditions, where farms are far apart, laboratories are only present in major centres and there are high ambient temperatures. In order to overcome the shortcomings associated with traditional diagnostic methods, the implementation of a molecular assay was sought. This work describes how a previously published PCR assay (MG3F/ MG4R primers) was adapted, optimised and applied in the diagnostic laboratory to test preputial samples directly for the presence of Campylobacter fetus. Field evaluation of the assay revealed an analytical sensitivity and specificity of 85.7% and 99%, respectively. Subsequent genotyping and phenotyping of a diverse collection of South African field isolates revealed that South Africa has an unexpected and previously unreported high incidence of Campylobacter fetus subsp. venerealis biovar intermedius strains. These strains were not identified correctly by the subspecies-specific primer set evaluated. Until such time that cost- effective genotyping methods are available to diagnostic laboratories in South Africa, and other countries with these atypical Campylobacter fetus subsp. venerealis strains, the need for bacterial culture will persist. Identification to subspecies level of isolates at present remains dependent upon a single phenotypic criterion, namely tolerance to 1% glycine.     

Effects of petroleum spray oils on oviposition behaviour and larval survival of Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) and Ostrinia nubilalis Hubner (Lepidoptera: Pyralidae)

We determined the effects of petroleum spray oil (PSO) (Caltex Canopy®) on oviposition responses of Helicoverpa armigera Hubner and Ostrinia nubilalis Hubner adults, and larval survival of the pest moths on cotton and maize plants in the laboratory. Application of 2% (v/v) of the PSO deterred H. armigera oviposition. Increasing the rate from 2 to 5% (v/v) did not significantly reduce the number of eggs laid by H. armigera on the treated plants. In contrast, the minimum rate at which the oil could deter oviposition of O. nubilalis on maize plants was 5% (v/v). Increasing the rate from 5 to 10% (v/v) did not significantly reduce the number of eggs laid per plant. However, a reduction in the rate of the PSO from 5 to 3% (v/v) resulted in a 73.9% increase in oviposition activity on the maize plants. In wind tunnel bioassay tests, all mated H. armigera females tested could detect and settle on plants treated with water but with plants treated with PSO at various times, only 50% of tested females settled on the plants 4?–?5 days after treatment (DAT) and none on the plants 0?–?2 DAT. A solid phase micro-extraction (SPME) test to determine the effect of the PSO on volatiles released by the cotton plants showed that the quantity of volatiles released by the cotton plants treated with PSO was lower than for water treated plants. This indicates that the PSO sprays may be suppressing or masking the leaf surface volatiles of the cotton plants, thereby deterring oviposition of H. armigera. Larval survival data show that PSO sprays can cause direct mortality of first, second and third instar O. nubilalis larvae. PSOs may have the potential to be integrated into pest management programme targeting H. armigera and O. nubilalis on cotton and maize crops, respectively.