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Orlando Borrashidalgo - One of the best experts on this subject based on the ideXlab platform.
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tobacco leaf spot and root rot caused by Rhizoctonia solani kuhn
Molecular Plant Pathology, 2011Co-Authors: Marleny Gonzalez, Merardo Pujol, Jeanpierre Metraux, Vicente Gonzalezgarcia, Melvin D Bolton, Orlando BorrashidalgoAbstract:SUMMARY Rhizoctonia solani Kuhn is a soil-borne fungal pathogen that causes disease in a wide range of plants worldwide. Strains of the fungus are traditionally grouped into genetically isolated anastomosis groups (AGs) based on hyphal anastomosis reactions. This article summarizes aspects related to the infection process, colonization of the host and molecular mechanisms employed by tobacco plants in resistance against R. solani diseases. Taxonomy: Teleomorph: Thanatephorus cucumeris (Frank) Donk; anamorph: Rhizoctonia solani Kuhn; Kingdom Fungi; Phylum Basidiomycota; Class Agaricomycetes; Order Cantharellales; Family Ceratobasidiaceae; genus Thanatephorus. Identification: Somatic hyphae in culture and hyphae colonizing a substrate or host are first hyaline, then buff to dark brown in colour when aging. Hyphae tend to form at right angles at branching points that are usually constricted. Cells lack clamp connections, but possess a complex dolipore septum with continuous parenthesomes and are multinucleate. Hyphae are variable in size, ranging from 3 to 17 µm in diameter. Although the fungus does not produce any conidial structure, ellipsoid to globose, barrel-shaped cells, named monilioid cells, 10–20 µm wide, can be produced in chains and can give rise to sclerotia. Sclerotia are irregularly shaped, up to 8–10 mm in diameter and light to dark brown in colour. Disease symptoms: Symptoms in tobacco depend on AG as well as on the tissue being colonized. Rhizoctonia solani AG-2-2 and AG-3 infect tobacco seedlings and cause damping off and stem rot. Rhizoctonia solani AG-3 causes ‘sore shin’ and ‘target spot’ in mature tobacco plants. In general, water-soaked lesions start on leaves and extend up the stem. Stem lesions vary in colour from brown to black. During late stages, diseased leaves are easily separated from the plant because of severe wilting. In seed beds, disease areas are typically in the form of circular to irregular patches of poorly growing, yellowish and/or stunted seedlings. Resistance: Knowledge is scarce regarding the mechanisms associated with resistance to R. solani in tobacco. However, recent evidence suggests a complex response that involves several constitutive factors, as well as induced barriers controlled by multiple defence pathways. Management: This fungus can survive for many years in soil as mycelium, and also by producing sclerotia, which makes the management of the disease using conventional means very difficult. Integrated pest management has been most successful; it includes timely fungicide applications, crop rotation and attention to soil moisture levels. Recent developments in biocontrol may provide other tools to control R. solani in tobacco.
Marleny Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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tobacco leaf spot and root rot caused by Rhizoctonia solani kuhn
Molecular Plant Pathology, 2011Co-Authors: Marleny Gonzalez, Merardo Pujol, Jeanpierre Metraux, Vicente Gonzalezgarcia, Melvin D Bolton, Orlando BorrashidalgoAbstract:SUMMARY Rhizoctonia solani Kuhn is a soil-borne fungal pathogen that causes disease in a wide range of plants worldwide. Strains of the fungus are traditionally grouped into genetically isolated anastomosis groups (AGs) based on hyphal anastomosis reactions. This article summarizes aspects related to the infection process, colonization of the host and molecular mechanisms employed by tobacco plants in resistance against R. solani diseases. Taxonomy: Teleomorph: Thanatephorus cucumeris (Frank) Donk; anamorph: Rhizoctonia solani Kuhn; Kingdom Fungi; Phylum Basidiomycota; Class Agaricomycetes; Order Cantharellales; Family Ceratobasidiaceae; genus Thanatephorus. Identification: Somatic hyphae in culture and hyphae colonizing a substrate or host are first hyaline, then buff to dark brown in colour when aging. Hyphae tend to form at right angles at branching points that are usually constricted. Cells lack clamp connections, but possess a complex dolipore septum with continuous parenthesomes and are multinucleate. Hyphae are variable in size, ranging from 3 to 17 µm in diameter. Although the fungus does not produce any conidial structure, ellipsoid to globose, barrel-shaped cells, named monilioid cells, 10–20 µm wide, can be produced in chains and can give rise to sclerotia. Sclerotia are irregularly shaped, up to 8–10 mm in diameter and light to dark brown in colour. Disease symptoms: Symptoms in tobacco depend on AG as well as on the tissue being colonized. Rhizoctonia solani AG-2-2 and AG-3 infect tobacco seedlings and cause damping off and stem rot. Rhizoctonia solani AG-3 causes ‘sore shin’ and ‘target spot’ in mature tobacco plants. In general, water-soaked lesions start on leaves and extend up the stem. Stem lesions vary in colour from brown to black. During late stages, diseased leaves are easily separated from the plant because of severe wilting. In seed beds, disease areas are typically in the form of circular to irregular patches of poorly growing, yellowish and/or stunted seedlings. Resistance: Knowledge is scarce regarding the mechanisms associated with resistance to R. solani in tobacco. However, recent evidence suggests a complex response that involves several constitutive factors, as well as induced barriers controlled by multiple defence pathways. Management: This fungus can survive for many years in soil as mycelium, and also by producing sclerotia, which makes the management of the disease using conventional means very difficult. Integrated pest management has been most successful; it includes timely fungicide applications, crop rotation and attention to soil moisture levels. Recent developments in biocontrol may provide other tools to control R. solani in tobacco.
S. Sarkar - One of the best experts on this subject based on the ideXlab platform.
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Antagonismus in vivo von fluoreszierenden Pseudomonaden gegenüber Rhizoctonia solani und Pythium aphanidermatum an Gurken und Buschbohnen
Anzeiger für Schädlingskunde Pflanzenschutz Umweltschutz, 1995Co-Authors: M. Wölk, S. SarkarAbstract:Fluoreszierende Pseudomonaden, die sich als Antagonisten in vitro gegenüber Rhizoctonia solani und Pythium aphanidermatum erwiesen haben, wurden an Gurken und Bohnen auf Antagonismus in vivo untersucht. Die Effizienz der Antagonisten in Auflaufversuchen gegenüber R. solani war niedriger als bei P. aphanidermatum . Die besten Isolate konnten in mit R. solani verseuchter Erde Auflaufraten von 30–40% erzielen, gegenüber P. aphanidermatum dagegen 40–60%. Die Wirkung der Antagonisten zur Verhütung von Spätinfektionen der Pflanzen war deutlich besser. So konnten 16 Isolate eine Schädigung durch R. solani an Bohnen zwischen 90 und 100% reduzieren. An Gurken konnten 12 Isolate eine Schädigung durch P. aphanidermatum auf 70–80% reduzieren. Fluorescent pseudomonads, which showed antagonism in vitro against Rhizoctonia solani and Pythium aphanidermatum, were investigated for antagonism in vivo using bean and cucumber. The efficiency of the antagonists in germination tests against Rhizoctonia solani was lower than against Pythium aphanidermatum. In soil infected with Rhizoctonia solani the germination rates of the seeds remained between 30 and 40%, whereas against Phytium aphanidermatum some Pseudomonas-strains caused germination rates of 40–60%. The preventive effect of the antagonists against fungal infection after the germination was better. 16 isolates reduced the damage caused by Rhizoctonia solani to bean between 90 and 100%. Damage caused by Pythium aphanidermatum to cucumber was reduced by 12 antagonists between 70 and 80%.
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Antagonism in vitro of fluorescent pseudomonads against Rhizoctonia solani and Pythium aphanidermatum
Zentralblatt für Mikrobiologie, 1993Co-Authors: M. Wölk, S. SarkarAbstract:Summary 1107 fluorescent pseudomonads were isolated from cucumber roots and 648 from the roots of beans and tested against Pythium aphanidermatum and Rhizoctonia solani . 934 Pseudomonas -strains, which were isolated from cucumbers, showed no antagonistic effect against Pythium aphanidermatum and 549 strains, isolated from beans, were not antagonistic against Rhizoctonia solani . We could show, that the antagonism of some antagonists is based not only on the production of siderophores.
Mitsuro Hyakumachi - One of the best experts on this subject based on the ideXlab platform.
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Biotransformation of l-menthol by soil-borne plant pathogenic fungi (Rhizoctonia solani)
Journal of Chemical Technology & Biotechnology, 2001Co-Authors: Mitsuo Miyazawa, Hideki Kawazoe, Mitsuro HyakumachiAbstract:The biotransformation of l-menthol was investigated by using nine isolates of Rhizoctonia solani (AG-1-IA Rs24, Joichi-2, RRG97-1; AG-1-IB TR22, R147, 110.4; AG-1-IC F-1, F-4 and P-1) as a biocatalyst. In the cases of Rhizoctonia solani F-1, F-4 and P-1, almost all of the substrate was consumed in 3 days and the major metabolite increased rapidly for the first of 3 days incubation. The structure of the major metabolite was elucidated on the basis of its spectral data. The major metabolite was determined to be (−)-(1S,3R,4S,6S)-6-hydroxymenthol which indicated that l-menthol was hydroxylated at the C-6 position. From the main component analysis, the nine isolates of Rhizoctonia solani were divided into two groups based on their ability to transform l-menthol to (−)-(1S,3R,4S,6S)-6-hydroxymenthol. This is the first report on the biotransformation of l-menthol by Rhizoctonia solani. © 2001 Society of Chemical Industry
Yang Jinghui - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity Determination of Rice Sheath Blight Pathogen(Rhizoctonia solani) to Boscalid
Guangdong Agricultural Sciences, 2011Co-Authors: Yang JinghuiAbstract:The sensitivity of 54 strains of rice sheath blight pathogen(Rhizoctonia solani) to Boscalid was determined with the method of mycelial growth rate,and the sensitivity baseline of the pathogen to Boscalid was established.The results showed that the EC50-value of Boscalid to the 54 strains varied from 0.4710 μg/mL to 2.0607 μg/mL with the mean of 1.0603 μg/mL.This average EC50-value could be regarded as the relative sensitivity baseline of Rhizoctonia solani to Boscalid because the 54 strains were collected from the rice fields where Boscalid was not applied,and the frequency distribution of the sensitivity of 54 strains to Boscalid showed a single-peak curve.