Alternaria jacinthicola, a new fungal species causing blight leaf disease on water hyacinth (Eichhornia crassipes (Martius) Solms-Laubach)

Water hyacinth (Eichhornia crassipes) causes environmental, agricultural and health problems in Mali. This is particularly severe in the District of Bamako and the irrigation systems of the “Office du Niger”area. During two years survey for fungal pathogens of water hyacinth infested areas, isolate Mlb684 was collected from diseased plant. This fungal isolate was identified as a potential mycoherbicide for sustainable management for water hyacinth. The aim of this study was to characterize isolate Mlb684. The characterization was based on a morphological description and a DNA sequence analysis. Various genes amplified from isolate Mlb684 were compared to those existing in Genbank. These genes were 18S ribosomal rDNA gene, ITS rDNA gene, elongation factor-1 alpha (EF1a) gene, calmodulin and actin genes. DNA sequence comparisons and morphological description provided enough evidences to show that isolate Mlb684 belonged to the Alternaria genus and was distinct from any other known Alternaria species. Based on these evidences, the new fungal isolate was called “Alternaria jacinthicola Dagno & M.H. Jijakli”. A specimen culture has been deposited in the Gembloux Agro Bio Tech Plant Pathology unit fungal collection, with Mlb684 reference and in the Industrial Fungal and Yeast Collection (BCCM/MUCL, Belgium) under the accession number: MUCL 53159 and all DNA sequences were deposited in GenBank (NCBI).Peer reviewe

Whole-Genome Sequences of 14 Strains of Bradyrhizobium canariense and 1 Strain of Bradyrhizobium japonicum Isolated from Lupinus spp. in Algeria

We report here the whole-genome sequences of 14 strains of Bradyrhizobium canariense, isolated from root nodules of Lupinus microanthus and Lupinus angustifolius, and 1 strain of Bradyrhizobium japonicum isolated from root nodules from Lupinus angustifolius in Algeria. These sequences add to the known diversity of this agronomically important genus

An unknown trees die back caused by Pseudomonas species in Switzerland

A model for tree pathogen diagnosis – Prunus domestica L. has been studied against pathogenic bacteria. An orchard of 110 trees of P. domestica showed dying back symptoms in May 2009 and nineteen of these trees were eradicated and burnt for prophylaxis. No symptoms correlated with those caused by pathogens previously observed in stone fruit die back in Europe or elsewhere (Pseudomonas syringae pv syringae van Hall, Pseudomonas syringae pv morsprunorum Lazarowtz, Phytophthora sp., Diaporthe perniciosa Marchal., phytoplasma or viruses) were not found. Interestingly, cutting the trunk in transversal sections allowed the observation of stem heart necrosis which was mostly important at the grafting point. Isolations from necrotic stem heart allowed to identify anot yet described Pseudomonas species not related to P. syringae. The method described in the paper for isolation of pathogenic bacteria and their quick an reliable identification can be also applied for detection of pathogens in forest tree plantations.Przemysław Szmi

Selection and mass production of santalum album l. calli for induction of sesquiterpenes

Young hypocotyl segments obtained from aseptically germinated seeds of Santalum album L. (5 weeks old) were used to induce callus formation. Growth of different calli types was induced on hypocotyls segments under different conditions. Resulting green calli were maintained on MS medium and Gamborg basal medium supplemented with 2,4D (2,4-Dichlorophenoxyacetic acid) (0.5 μM) and Kin (Kinetin) (10 μM). Numerous concentrations of 2,4D and Kin were tested in combination with inducers of the sesquiterpene metabolism and one promising callus type was selected for mass production. This interesting type of callus has been used for searching functional genes in the biosynthetic pathway leading to sesquiterpenes molecules

Impact of invading species on biodiversity ::diet study of the green whip snake’s (Hierophis viridiflavus, L. 1789) in Switzerland

Next-generation sequencing is increasingly used in conservation biology to resolve complex interactions between species, either diet or gut parasites studies. We applied a recent long metabarcoding method to elucidate the green whip snake’s (Hierophis viridiflavus) prey consumption based on DNA extracted from stomach contents. Illegally introduced in Canton of Vaud (Switzerland), three populations of the green whip snake have strongly developed in two regions, East (Chablais) and North. We suspect that this introduced species is threatening part of the local herpetofauna, especially the Asp viper and the Western green lizard in this region. Consequently, an extermination program has been implemented from 2016 to mitigate Hierophis viridiflavus expansion and its impact arising from its generalist diet. Stomach contents of 94 individuals removed from introduction sites were analysed by long metabarcoding. Our study revealed the consumption of 67 prey belonging to 9 species, primarily small mammals and reptiles. The recurrent presence of two parasitic nematodes was also discovered. Although cannibalistic behaviour could not be highlighted with this approach, a scavenging behaviour was suspected based on the presence of an insect used in forensic entomology (Calliphora vicina). These results confirm the opportunistic feeding behaviour of Hierophis viridiflavus and its ability to predate on threatened species. Although 86.6 % of preys were not listed on the Swiss Red List, the impact on the Asp viper population can be important (up to 20 % of consumed preys) and could partially explain its strong decline

Oregano essential oil vapour prevents Plasmopara viticola infection in grapevine (Vitis Vinifera) and primes plant immunity mechanisms

The reduction of synthetic fungicides in agriculture is necessary to guarantee a sustainable production that protects the environment and consumers’ health. Downy mildew caused by the oomycete Plasmopara viticola is the major pathogen in viticulture worldwide and responsible for up to 60% of pesticide treatments. Alternatives to reduce fungicides are thus utterly needed to ensure sustainable vineyard-ecosystems, consumer health and public acceptance. Essential oils (EOs) are amongst the most promising natural plant protection alternatives and have shown their antibacterial, antiviral and antifungal properties on several agricultural crops. However, the efficiency of EOs highly depends on timing, application method and the molecular interactions between the host, the pathogen and EO. Despite proven EO efficiency, the underlying processes are still not understood and remain a black box. The objectives of the present study were: a) to evaluate whether a continuous fumigation of a particular EO can control downy mildew in order to circumvent the drawbacks of direct application, b) to decipher molecular mechanisms that could be triggered in the host and the pathogen by EO application and c) to try to differentiate whether essential oils directly repress the oomycete or act as plant resistance primers. To achieve this a custommade climatic chamber was constructed that enabled a continuous fumigation of potted vines with different EOs during long-term experiments. The grapevine (Vitis vinifera) cv Chasselas was chosen in reason of its high susceptibility to Plasmopara viticola. Grapevine cuttings were infected with P. viticola and subsequently exposed to continuous fumigation of different EOs at different concentrations, during 2 application time spans (24 hours and 10 days). Experiments were stopped when infection symptoms were clearly observed on the leaves of the control plants. Plant physiology (photosynthesis and growth rate parameters) were recorded and leaves were sampled at different time points for subsequent RNA extraction and transcriptomics analysis. Strikingly, the Oregano vulgare EO vapour treatment during 24h post-infection proved to be sufficient to reduce downy mildew development by 95%. Total RNA was extracted from leaves of 24h and 10d treatments and used for whole transcriptome shotgun sequencing (RNA-seq). Sequenced reads were then mapped onto the V. vinifera and P. viticola genomes. Less than 1% of reads could be mapped onto the P. viticola genome from treated samples, whereas up to 30% reads from the controls mapped onto the P. viticola genome, thereby confirming the visual observation of P. viticola absence in the treated plants. On average, 80% of reads could be mapped onto the V. vinifera genome for differential expression analysis, which yielded 4800 modulated genes. Transcriptomic data clearly showed that the treatment triggered the plant’s innate immune system with genes involved in salicylic, jasmonic acid and ethylene synthesis and signaling, activating Pathogenesis-Related-proteins as well as phytoalexin synthesis. These results elucidate EO-host-pathogen interactions for the first time and indicate that the antifungal efficiency of EO is mainly due to the triggering of resistance pathways inside the host plants. This is of major importance for the production and research on biopesticides, plant stimulation products and for resistance-breeding strategies

Comment contrer biologiquement cylindrocladium buxicola et volutella buxi

Après un premier article sur la lutte contre la pyrale du buis, nous traitons ici d'essais de lutte biologique contre les champignons cylindrocladium buxicola et volutella buxi

Whole-genome shotgun sequence of pseudomonas viridiflava, a bacterium species pathogenic to ararabidopsis thaliana

We report here the first whole-genome shotgun sequence of Pseudomonas viridiflava strain UASWS38, a bacterium species pathogenic to the biological model plant Arabidopsis thaliana but also usable as a biological control agent and thus of great scientific interest for understanding the genetics of plant-microbe interactions

Whole-genome sequence of enteractinococcus helveticum sp. nov. strain UASWS1574 isolated from industrial used waters

We report here the whole-genome shotgun sequences of the strain UASWS1574 of the undescribed Enteractinococcus helveticum sp. nov., isolated from used water. This is the first genome registered for the whole genus