Chalara fraxinea is an invasive pathogen in France

Decline induced by Chalara fraxinea is an emerging disease that severely affects ash stands in Europe. The disease appears to have an invasive spread from East to West of Europe in the last decade. The teleomorphic stage, Hymenoscyphus pseudoalbidus, that occurs as apothecia on ash rachis in the litter was recently described. The origin of ash decline remains unclear as a cryptic species, H. albidus, a long-established fungus in Europe, could be present in the same niche, and as in Switzerland, H. pseudoalbidus was shown to have been present long before the recent epidemic outbreak. In France, the emerging disease is very recent and clearly restrained to Northeastern France. We thus collected isolates from infected hosts and from apothecia/ash rachis both inside and outside the infected area in France in order to compare them on the basis of pathogenicity towards ash seedlings and sequences of the ITS regions and of three single-copy genes. We showed that two population types exhibiting about 2% base pair polymorphism in the sequences analysed were present in Northern France. The first type, corresponding to H. pseudoalbidus, was present on rachis and infected hosts only in Northeastern France and showed strong pathogenicity towards ash seedlings in inoculation tests. By contrast, the second type, which corresponds to H. albidus, was present throughout Northern France and showed no pathogenicity towards ash seedlings. Our study confirms the results of Queloz et al. (2010) who presented molecular evidences for the existence of two cryptic species, H. albidus and H. pseudoalbidus. The results strongly suggest that Chalara fraxinea/H. pseudoalbidus is a recent invader in France.     

Influence of microflora and composition of root bathing solution on root exudation of maize plants

Root exudation of carbon (C) plays a major role in processes occurring in the plant rhizosphere. Environmental factors affecting root exudation have been identified but their effects are rarely quantified. The purpose of this work was to evaluate the impact of both the microflora and the chemical composition of the growth medium on root exudation, taking into account soluble exudates and mucilage fraction. Maize plants (Zea mays L.) were grown for 12 days in hydroponic conditions and then transferred in three root bathing solutions (demineralized water, KCl or nutrient solution) during 24 hours. In each case, presence of microflora was tested with a comparison between plants inoculated with maize rhizospheric strain and axenic plants. Exudation was measured in terms of C and biomass production. A strong interaction was noticed between microflora and chemical composition of the root bathing solution. In fact, the presence of rhizospheric microflora induces a stimulation of soluble exudates only in KCl and Nutrient solutions. In demineralized water, a different response was observed with a higher C release for axenic plants, probably due to the osmotic shock induced to the roots. Concerning mucilage fractions, small quantities were recovered on all treatments. This work demonstrates that the chemical composition of the root bathing solution and presence of microorganisms significantly modify the amount of soluble exudates. Attention must therefore be paid to the cultural conditions when exudation is studied because of the sensitivity of this process to root environment.     

Assessing the effects of subtropical forest fragmentation on leaf nitrogen distribution using remote sensing data

Subtropical forest loss resulting from conversion of forest to other land-cover types such as grassland, secondary forest, subsistence crop farms and small forest patches affects leaf nitrogen (N) stocks in the landscape. This study explores the utility of new remote sensing tools to model the spatial distribution of leaf N concentration in a forested landscape undergoing deforestation in KwaZulu-Natal, South Africa. Leaf N was mapped using models developed from RapidEye imagery; a relatively new space-borne multispectral sensor. RapidEye consists of five spectral bands in the visible to near infra-red (NIR) and has a spatial resolution of 5 m. MERIS terrestrial chlorophyll index derived from the RapidEye explained 50 % of the variance in leaf N across different land-cover types with a model standard error of prediction of 29 % (i.e. of the observed mean leaf N) when assessed on an independent test data. The results showed that indigenous forest fragmentation leads to significant losses in leaf N as most of the land-cover types (e.g. grasslands and subsistence farmlands) resulting from forest degradation showed lower leaf N when compared to the original indigenous forest. Further analysis of the spatial variation of leaf N revealed an autocorrelation distance of about 50 m for leaf N in the fragmented landscape, a scale corresponding to the average dimension of subsistence fields (2,781 m²) in the region. The availability of new multispectral sensors such as RapidEye thus, moves remote sensing closer to widespread monitoring of the effect of tropical forest degradation on leaf N distribution.     

A sensitive real-time PCR assay for the detection of the two Melampsora medusae formae speciales on infected poplar leaves

Melampsora medusae is a quarantine fungus in the European Union (EU) that causes a damaging leaf rust disease on poplars. Two formae speciales of the pathogen can be distinguished, M. medusae f. sp. deltoidae and M. medusae f. sp. tremuloidae, but the EU plant health directive 2000/29/EC currently in force does not make the distinction between them. EU countries must have the ability to detect and identify rapidly the introduction of these quarantine fungi and to conduct extensive surveys in case of outbreaks. Efficient detection tools are thus needed. In this study, a sensitive real-time PCR assay was developed to detect the presence of M. medusae in poplar leaf samples. A unique primer/hydrolysis probe combination targeting both formae speciales was designed using species-specific polymorphisms observed within the internal transcribed spacer region. An additional primer/hydrolysis probe combination was designed from a region of the 28S rDNA that is highly conserved in the genus Melampsora and used in a separate real-time PCR assay in order to check the quality of the DNA extracted from Melampsora urediniospores. The test developed demonstrated a high sensitivity since it enables the reproducible detection of two M. medusae urediniospore in a mixture of 2 mg of urediniospores (ca 800 000 urediniospores) of other Melampsora species. This new real-time PCR tool should be useful for laboratories in charge of official analyses since it has many advantages over the techniques currently used to monitor this quarantine pathogen in Europe.     

Effect of timing and duration of salt treatment during growth of a fragrant rice variety on yield and 2-acetyl-1-pyrroline, proline, and GABA Levels

In greenhouse experiments, Aychade, a fragrant rice variety, was grown under one level of salt solution (EC of 3800 ± 400 μS·cm(-1)) sufficient to induce salt stress in rice. Timing and duration of salt solution application varied according to the growth stages. 2-Acetyl-1-pyrroline (2AP), a characteristic flavor compound of fragrant rice as well as biogenetically related compounds, proline, and γ-aminobutyric acid (GABA) were quantified. Salt treatments induced 2AP synthesis in the leaves, but the increase was often higher in the vegetative phase. This increase was correlated with proline level but not with that of GABA. Interestingly the grains from all the salt treated plants contained significantly higher levels of 2AP (733-998 μg·kg(-1)) than those from the control (592 μg·kg(-1)). The highest 2AP synthesis occurred when the plants were subjected to salt treatment during whole vegetative or reproductive phases. However in the latter case crop yield decreased significantly.     

Prospective echocardiographic and tissue Doppler screening of a large Sphynx cat population: Reference ranges,heart disease prevalence and genetic aspects

Objectives(1) To investigate heart morphology and function using echocardiography and tissue Doppler imaging (TDI), (2) to determine heart disease prevalence and characteristics, and (3) to assess potential genetic features in a population of Sphynx cats presented for cardiovascular screening.AnimalsA total of 147 echocardiographic examinations, including 33 follow-ups, were performed by trained observers on 114 Sphynx cats of different ages (2.62 ± 1.93 years [0.5–10.0]) from 2004 to 2011.MethodsSphynx cats underwent a physical examination, conventional echocardiography, and, if possible, two-dimensional color TDI.ResultsConventional echocardiographic findings included 75/114 normal (65.8%) and 39/114 (34.2%) abnormal examinations with a diagnosis of either congenital heart diseases (n = 16) or hypertrophic cardiomyopathy (HCM, n = 23). In adult healthy cats, a significant body weight effect was observed for several echocardiographic variables, including end-diastolic left ventricular (LV) free wall (P < 0.01), interventricular septum (P < 0.001), and LV diameter (P < 0.001). Mitral valve dysplasia (MVD) was observed as a single or associated defect in 15/16 cats with congenital heart diseases. A significant increase in HCM prevalence (P < 0.001) was observed according to age. The pedigree analysis of a large family (n = 81) suggested an autosomal dominant mode of inheritance with incomplete penetrance for HCM.ConclusionsBody weight should be taken into account when interpreting values of diastolic myocardial wall thicknesses in Sphynx cats. Additionally, HCM and MVD are two relatively common heart diseases in this feline breed. More pedigree data are required to confirm the inheritance pattern of HCM at the breed level.     

Towards the identification of ecological management units: A multidisciplinary approach for the effective management of bottlenose dolphins in the southern Iberian Peninsula

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Assessment of age at first parturition by accounting censored data: the example of small ruminants in agropastoral herds in Senegal

Age at first parturition (AFP) is an important reproductive trait when evaluating the herd productivity in tropical small-holder farming systems, particularly for small ruminants with high demographic turnover and commercial utilization. The article reports the AFP probability distributions calculated on goats and sheep herds monitored for more than 10 years in three low-input livestock farming systems located from northern to southern Senegal (Louga, Kaymor, and Kolda) and representing different agroecological conditions and animal phenotypes. The AFP distributions were estimated with the Kaplan–Meier (KM) survival analysis accounting for censoring (females lost to follow-up before their first parturition). When measured by the KM estimator of the AFP median, the precocity for both species was almost 4 months later in Louga than in Kaymor and Kolda. In Louga, the precocity was 1.6 months later for sheep than for goats and 2.9 months in Kaymor and Kolda. These estimates were higher than those obtained with the common and crude approach that removes censored data before calculation (relative bias ranged from −12% to −22% for the AFP mean depending on species and site) and those already published in previous studies on the same data sets. In on-farm small ruminant studies focusing on reproductive traits such as AFP distributions, we recommend using survival models (e.g., the KM method) to avoid potential biases due to data censoring.