Microdochium nivale (Fr.) Samuels & Hallett and Microdochium majus (Wollenw.) Glynn & S.G. Edwards are sister species that cause diseases on grasses and cereals at low temperatures. The DNA sequences of RPB2 (RNA polymerase II), -tubulin, EF-1␣ (elongation factor), and ITS (rDNA internal transcribed spacer) from these groups were analysed to compare the extent of differences between these species, among isolates from Europe compared with those from North America, and among isolates of M. nivale originally collected from Agrostis spp. compared with isolates from wheat (Triticum aestivum). All of the regions studied except for ITS resolved M. nivale and M. majus isolates into separate clades. The RPB2 sequences also resolved both the North American and European M. majus isolates and M. nivale isolates from either turfgrasses or wheat into separate clades. These results support the recent elevation of M. nivale and M.majus to sister species and also provide some support for the assertion that there may be host-specific differences among M. nivale, which has a wider host range than M. majus. Résumé: Le Microdochium nivale (Fr.) Samuels & Hallett et le Microdochium majus (Wollenw.) Glynn & S.G. Edwards constituent deux plantes soeurs causant des maladies chez les herbacées et les céréales à basse température. Afin de comparer l'étendue des différences entre ces deux espèces, les auteurs ont analysé la séquence ADN du RBP2 (polymérase de l'ARN II), la -tubuline, le EF-1␣ (facteur d'élongation) et l'ITS (espaceur interne transcrit du rADN) chez ces groupes, entre isolats d'Europe comparés à ceux de l'Amérique du Nord; également entre des isolats du M. nivale originalement récoltés d'Agrostis spp. comparativement à des isolats provenant du blé. (Triticum aestivum). Toutes les régions étudiées, sauf pour l'ITS, regroupent les isolats de M. nivale et du M. majus dans des clades séparés. Les séquences RBP2 distinguent également les isolats du M. majus européens et nord-américains et les isolats du M. nivale provenant soit d'herbacées ou de blé dans des clades distincts. Ces résultats supportent l'élévation récente du M. nivale et du M. majus en espèces soeurs, et fournit également un certain support à l'affirmation qu'il pourrait exister des différences spécifiques à l'hôte parmi les M. nivale ayant un nombre d'hôtes plus large que le M. majus. [Traduit par la Rédaction]Mots-clés : Microdochium nivale, Microdochium majus, maladie des plantes, moisissure nivéale rose, plaque de Fusarium, plaque de Microdochium.
Plant pathogens pose a significant threat to the food industry and food security accounting for 10-40% crop losses annually on a global scale. Economic losses from plant diseases are estimated at $300B for major food crops and are associated with reduced food availability and accessibility and also high food costs. Although strategies exist to reduce the impact of diseases in plants, many of these introduce harmful chemicals to our food chain. Therefore, it is important to understand and utilize plants' immune systems to control plant pathogens to enable more sustainable agriculture. Lipids are core components of cell membranes and as such are part of the first line of defense against pathogen attack. Recent developments in omics technologies have advanced our understanding of how plant membrane lipid biosynthesis, remodelling and/or signalling modulate plant responses to infection. Currently, there is limited information available in the scientific literature concerning lipid signalling targets and their biochemical and physiological consequences in response to plant pathogens. This review focusses on the functions of membrane lipid derivatives and their involvement in plant responses to pathogens as biotic stressors. We describe major plant defense systems including systemic-acquired resistance, basal resistance, hypersensitivity and the gene-for-gene concept in this context. 1 | INTRODUCTION The advancement in global agricultural production, the food industry and food security necessitates consideration of the impact of infectious pathogens on plants. This is because pathogens are widely recognized as significant obstacles to important and dependable food systems (Savary et al., 2019). Recent reports have demonstrated that plant diseases pose a significant threat to the food industry and to food security accounting for 10 to 40% crop losses annually on a global scale. Economic losses from plant diseases are estimated at $300B for major food crops, and diseases are associated with reduced food production, availability and accessibility as well as high food costs (Fletcher et al., 2006; Savary et al., 2019). Plants face different biotic stresses during their life cycle. For instance, a variety of diseases are caused by fungi, bacteria, protozoa, nematodes, viruses and phytoplasmas. These pathogens change favourable growing environments for plants into unfavourable conditions, particularly during susceptible growth stages. These cause significant yield losses both in greenhouses and under field conditions. Therefore, it is important to understand and utilize plants' innate immune systems to control plant pathogens to enable more sustainable agriculture (Brackin, Atkinson, Sturrock, & Rasmussen, 2017). Natural defense mechanisms involve a variety of signalling events and responses, which serve to combat intruding pathogens. The defense mechanism is categorized into constitutive and induced defense mechanisms. As the first line of defense, constitutive mechanisms utilize pre-formed chemicals and barriers such as ce...
This study investigated the antibacterial activity of glycolipid-rich extracts of the brown macroalga Fucus evanescens in cell culture. Accessions were collected on the Arctic coast of Ungava Bay, Nunavik, Quebec. The crude ethyl acetate extract of these accessions showed strong antibacterial activity (≥4 log(10) cfu) against Hemophilus influenzae , Legionella pneumophila , Propionibacterium acnes (ATCC and clinical isolate), and Streptococcus pyogenes at 100 µg/mL. This algal extract inhibited by 3 log(10) Clostridium difficile and methicillin-resistant Staphylococcus aureus , whereas Bacillus cereus , Escherichia coli , Klebsiella pneumoniae , and Pseudomonas aeruginosa were not significantly affected. Further investigations of the activity of a glycolipid-rich fraction, extracted with dichloromethane, against Propionibacterium acnes showed an MIC(100) of 50 µg/mL, with an inhibition of more than 99% at only 7.8 µg/mL. The main active compound, a β-d-galactosyl O-linked glycolipid, was synthesized for the bioassay and showed an MIC(100) of 50 µg/mL but lost its activity more quickly with only 50% of inhibition at 12.5 µg/mL. Therefore, the semipurified F. evanescens extract could be a good choice for future research into the development of alternative treatments for acne therapy.
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