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Nachaat Sakr - One of the best experts on this subject based on the ideXlab platform.
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Intra- and inter-isolate variation in two predominant Plasmopara halstedii (sunflower downy mildew) races in Europe
2020Co-Authors: Nachaat SakrAbstract:Morphological, pathogenic and genetic variation was studied in two Plasmopara halstedii (sunflower downy mildew) races 100 and 710 using five single zoosporangium isolates per pathogen isolate. Aggressiveness criteria were analysed in one sunflower inbred line showing a high level of quantitative resistance. Morphological analyses were carried out on Zoosporangia and sporangiophores for single zoosporangium isolates. Genetic relationships were detected among the single zoosporangium isolates using 12 EST (Expressed Sequence Tag)-derived markers. Index of aggressiveness was calculated for each isolate and revealed the presence of significant differences in and between single zoosporangium isolates of two races 100 and 710. There were significant morphological differences for pathogen single zoosporangium isolates. There was no relation between Zoosporangia and sporangiophore morphology and race virulence profiles or aggressiveness criteria. There was no intra-isolate genetic variation for the two pathogen races, but major genetic variation was observed between single zoosporangium isolates of the two races 100 and 710. A correlation was detected between pathogenicity traits and EST genotypes.
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Variation in form and size of Plasmopara halstedii (sunflower downy mildew) Zoosporangia
Mycological Progress, 2015Co-Authors: Nachaat Sakr, Jeanne Tourvieille, Mireille Ducher, Pascal Walser, Denis Tourvieille de LabrouheAbstract:Zoosporangia form and size were studied on a collection of 94 strains of Plasmopara halstedii (sunflower downy mildew). Both oval and round forms were present in all strains analysed. The proportion of two forms varied significantly according to strain and plant age but more especially to host plant genotype. Whatever the strain or host genotype, oval Zoosporangia were larger than round ones, but there was no relation between the proportion of the oval form and mean Zoosporangia size. There was no relation between Zoosporangia form or size and race virulence profiles or aggressiveness criteria, with the possible exception of Zoosporangia size and sporulation density. It is concluded that, for this obligate parasite, although form and size of Zoosporangia depend on pathogen strain, these characters also vary according to growth conditions of Plasmopara halstedii, in particular to the genotype of the plant host.
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Diversity in Plasmopara halstedii, the causal agent of sunflower downy mildew
Cryptogamie Mycologie, 2015Co-Authors: Nachaat SakrAbstract:Diversity of the level of morphological, pathogenic and genetic characteristics was studied in seven Plasrnopara halstedii (sunflower downy mildew) isolates of seven races namely 100, 300, 304, 314, 710, 704 and 714. All analyses were carried out by using five single zoosporangium isolates per pathogen isolate. Morphological analyses were performed on Zoosporangia for P. halstedii single zoosporangium isolates. Aggressiveness criteria were analysed in one sunflower inbred line showing a high level of quantitative resistance. Genetic relationships were detected between the single zoosporangium isolates using 12 EST-derived as SNPs markers. Based on the aggressiveness reaction for the P. halstedii single zoosporangium isolates, there were significant intra and inter-race differences for all criteria studied. Isolates of races 100 and lac were less virulent and more aggressiveness than isolates of races 7xx. There was no relation between morphology of Zoosporangia and pathogenic characteristics for 35 single zoosporangium isolates. There was no intra-race genetic variation, but five genetically-identified groups were detected among pathogen isolates of all races. No correlation was detected between EST genotypes on the one hand and both pathogenic traits and morphological characteristics on the other.
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PHENOTYPIC GROUPS OF PLASMOPARA HALSTEDII (DOWNY MILDEW) BASED ON INTERACTIONS WITH SUNFLOWER PLANTS
Acta Botanica Hungarica, 2013Co-Authors: Nachaat SakrAbstract:Phenotypic groups including pathogenic, morphological and genetic characteristics for 50 Plasmopara halstedii (downy mildew) isolates belonging to seven races based on interactions with sunflower plants were revealed. Pathogenicity for pathogen isolates were analysed in sunflower plants showing different levels of resistance. Based on the reaction for the P. halstedii isolates to sunflower hybrids varying only in Pl resistance genes, there were three identified groups based on virulence reaction. Index of aggressiveness was calculated for pathogen isolates and revealed the presence of significant differences between isolates of 100 and 3xx races (more aggressive) and isolates of 710 and 7xx races (less aggressive). Morphological analyses were carried out on Zoosporangia and sporangiophores for P. halstedii isolates produced on the surface of cotyledons in sunflower plants infected thought roots. There were no groups based on the morphology of Zoosporangia and sporangiophores for pathogen isolates. Genetic relationships were detected between pathogen isolates using 12 EST-derived markers. There was no intra-race genetic variation, but five genetically-identified groups were detected among pathogen isolates of all races. Combining data of pathogen’s variation with variability in sunflower to arrive at durable resistance against P. halstedii was discussed.
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Diversity in Plasmopara halstedii, the Causal Agent of Sunflower Downy Mildew
Cryptogamie Mycologie, 2012Co-Authors: Nachaat SakrAbstract:Abstract Diversity of the level of morphological, pathogenic and genetic characteristics was studied in seven Plasmopara halstedii (sunflower downy mildew) isolates of seven races namely 100, 300, 304, 314, 710, 704 and 714. All analyses were carried out by using five single zoosporangium isolates per pathogen isolate. Morphological analyses were performed on Zoosporangia for P. halstedii single zoosporangium isolates. Aggressiveness criteria were analysed in one sunflower inbred line showing a high level of quantitative resistance. Genetic relationships were detected between the single zoosporangium isolates using 12 EST-derived as SNPs markers. Based on the aggressiveness reaction for the P. halstedii single zoosporangium isolates, there were significant intra and inter-race differences for all criteria studied. Isolates of races 100 and 3xx were less virulent and more aggressiveness than isolates of races 7xx. There was no relation between morphology of Zoosporangia and pathogenic characteristics for 3...
Denis Tourvieille de Labrouhe - One of the best experts on this subject based on the ideXlab platform.
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Variation in form and size of Plasmopara halstedii (sunflower downy mildew) Zoosporangia
Mycological Progress, 2015Co-Authors: Nachaat Sakr, Jeanne Tourvieille, Mireille Ducher, Pascal Walser, Denis Tourvieille de LabrouheAbstract:Zoosporangia form and size were studied on a collection of 94 strains of Plasmopara halstedii (sunflower downy mildew). Both oval and round forms were present in all strains analysed. The proportion of two forms varied significantly according to strain and plant age but more especially to host plant genotype. Whatever the strain or host genotype, oval Zoosporangia were larger than round ones, but there was no relation between the proportion of the oval form and mean Zoosporangia size. There was no relation between Zoosporangia form or size and race virulence profiles or aggressiveness criteria, with the possible exception of Zoosporangia size and sporulation density. It is concluded that, for this obligate parasite, although form and size of Zoosporangia depend on pathogen strain, these characters also vary according to growth conditions of Plasmopara halstedii, in particular to the genotype of the plant host.
A. P. Kole - One of the best experts on this subject based on the ideXlab platform.
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Some observations on the zoospores from the Zoosporangia ofPlasmodiophora brassicae Woron@@@Enkele waarnemingen betreffende de zoösporen uit de zoösporangia van Plasmodiophora brassicaeWoron
European Journal of Plant Pathology, 2020Co-Authors: A. P. KoleAbstract:Het onderzoek had ten dcel het gedrag van de zoosporen uit de Zoosporangia vanPlasmodiophora brassicae na te gaan. Aangetaste worteltjes van jonge koolplanten, opgekweekt in zwaarbesmette grond, werden goed afgespoeld en in stukjes ter lengte van 2–3 cm geknipt. Hiervan werden waterpreparaten gemaakt, waarin na ongeveer 30 min. de zoosporen uit de Zoosporangia begonnen vrij te komen. Het merendeel van de zoosporen had een lange en een korte zweepdraad, maar bij sommige zoosporen werden twee lange en twee korte zweepdraden waargenomen. Enkele malen werd waargenomen, dat twee zoosporen, door een draadvormige verbinding aan elkaar gekoppeld, op korte onderlinge afstand gepaard rondzwommen. In preparaten met gekleurde zoosporen werden behalve zoosporen met een lange en een korte zweepdraad, ook zoosporen met twee lange en twee korte, drie lange en drie korte en zelfs vier lange en vier korte zweepdraden aangetroffen. Op grond van deze waarnemingen wordt — in overeenstemming met hetgeen van de nauw aanP. brassicae verwante schimmelSpongospora subterranea bekend is — geconcludeerd, dat samengestelde zoosporen ontstaan doordat twee of meer enkelvoudige zoosporen versmelten. Het is niet uitgesloten, dat deze versmelting van zoosporen het begin is van een geslachtelijke phase in de levensloop van de schimmel, maar een kernversmelting in de samengestelde zoosporen kon niet worden aangetoond.
Jose Miguel Cotes Torres - One of the best experts on this subject based on the ideXlab platform.
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efecto de la infeccion de spongospora subterranea f sp subterranea en hospederos alternos
Revista Facultad Nacional de Agronomía - Medellín, 2014Co-Authors: Ivon Magaly Arcila Aristizabal, Elena Paola Gonzalez Jaimes, Catalina Maria Zuluaga Amaya, Mauricio Marin Montoya, Jose Miguel Cotes TorresAbstract:Trap crops have been considered an alternative strategy to reduce the inoculum of soil pathogens such as Spongospora subterranea f.sp. subterranea . In this work, the incidence of this pathogen was evaluated at three consecutive sowings using different alternative hosts. Plants were sown in pots containing 2 kg of soil inoculated with 1x105 cystosori per gram and harvested every three months. Roots were tested for the presence of cystosori and Zoosporangia using light microscopy observations with trypan blue (0.05%) and Real-time PCR (qPCR). Data fitting was performed using Exponential and monomolecular models. According to the estimated incidence values of pathogen structures, plant species Cyphomandra betacea , Physalis peruvianum , Solanum nigrum , Allium cepa , Solanum quitoense and Rumex crispus , significantly reduced the amount of cystosori and Zoosporangia after the three consecutive sowings. In contrast, Petroselinum crispum , Pennisetum clandestinum , Zea mays and Solanum lycopersicum increased the incidence of S. subterranea f. sp. subterranea .
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efecto de la infeccion de spongospora subterranea f sp subterranea en hospederos alternos effect of spongospora subterranea f sp subterranea infection on alternate hosts
Revista Facultad Nacional de Agronomía, 2014Co-Authors: Ivon Magaly Arcila Aristizabal, Elena Paola Gonzalez Jaimes, Catalina Maria, Zuluaga Amaya, Mauricio Alejandro, Marin Montoya, Jose Miguel Cotes TorresAbstract:Trap crops have been considered an alternative strategy to reduce the inoculum of soil pathogens such as Spongospora subterranea f.sp. subterranea. In this work, the incidence of this pathogen was evaluated at three consecutive sowings using different alternative hosts. Plants were sown in pots containing 2 kg of soil inoculated with 1x10 5 cystosori per gram and harvested every three months. Roots were tested for the presence of cystosori and Zoosporangia using light microscopy observations with trypan blue (0.05%) and Real-time PCR (qPCR). Data fitting was performed using Exponential and monomolecular models. According to the estimated incidence values of pathogen structures, plant species Cyphomandra betacea, Physalis peruvianum, Solanum nigrum, Allium cepa, Solanum quitoense and Rumex crispus, significantly reduced the amount of cystosori and Zoosporangia after the three consecutive sowings. In contrast, Petroselinum
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alternate hosts of spongospora subterranea f sp subterranea identification in colombia by bioassay identificacion de hospederos alternos de spongospora subterranea f sp subterranea en colombia por bioensayos
Revista Facultad Nacional de Agronomía, 2013Co-Authors: Ivon Magaly, Arcila Aristizabal, Elena Paola Gonzalez Jaimes, Catalina Maria, Zuluaga Amaya, Jose Miguel Cotes TorresAbstract:Potato powdery scab, caused by Spongospora subterranea f. sp. subterranea, is a disease that limits worldwide potato crop production. Incidence of the disease has been increasing in Colombia, thereby affecting tubers production, so far effective control methods have yet to be developed. The aim of this research was to establish the host range plants for Spongospora subterranea f. sp. subterranea by artificial inoculations. Thus, 33 species were inoculated with 1×10 6 sporosori . mL -1 solution for 12 days. The plants were then planted in field, evaluations were performed at 15, 30, 60, 90 and 120 days after inoculation, 10 plants of each species were selected for every evaluation, the roots were stained and the pathogenic structures were identified by microscopy. Morphological examination enabled the identification of trap plants species, which presented Zoosporangia only; Type I hosts, which present sporosori only; and Type II hosts, which presented both sporosori and Zoosporangia. Some of these hosts belonged to the Alliaceae, Apiaceae, Brassicaceae, Poaceae, Polygonaceae and Solanaceae families, thus extending the species range that can be reported as hosts of Spongospora subterranea f. sp. subterranea in Colombia.
V N Tariq - One of the best experts on this subject based on the ideXlab platform.
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factors influencing Zoosporangia formation by phytophthora fragariae in vitro
Fungal Biology, 1990Co-Authors: V N TariqAbstract:Factors influencing asexual sporulation in vitro were studied for three isolates of Phytophthora fragariae. Maximum numbers of Zoosporangia were obtained when an 11 or 15 mm diam disc, cut at the edge of a 15- or 20-d-old colony on a semi-defined medium, was incubated in 6 ml sterile glass-distilled water, in a 4·5 cm diam Petri dish, at 13 or 22°C, depending on the isolate. Isolates varied in their response to the addition of nutrients to the flooding medium. Although visible light had no effect on asexual sporulation near-uv radiation inhibited Zoosporangia production by two of the isolates. The role of nutrients as promoters and/or inhibitors of Zoosporangia formation is discussed.