Studies on the genus Pythium in Egypt. V. Test of pathogenicity of some common root-infecting fungi in Egypt
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Pathogenicity tests of various species of <i>Pythium, Fusarium</i> and <i>Rhizoctonia sotani</i> were made on five plants namely cotton, pea, tomato, maize and wheat. <i>Pythium ultimum proved to be the most destructive species to tomato and cotton seedlings. The four species of <i>Fusarium</i> tested showed considerably different pathogenic abilities. Isolate of <i>Rhizoctonia soleni</i> (A — from soil) showed slight pathogenicity to all test plants and isolate (B — from cotton seedlings) was highly destructive to cotton and pea.Keywords:
Rhizoctonia
Pythium
Pythium ultimum
Root rot
Pathogenicity tests of various species of <i>Pythium, Fusarium</i> and <i>Rhizoctonia sotani</i> were made on five plants namely cotton, pea, tomato, maize and wheat. <i>Pythium ultimum proved to be the most destructive species to tomato and cotton seedlings. The four species of <i>Fusarium</i> tested showed considerably different pathogenic abilities. Isolate of <i>Rhizoctonia soleni</i> (A — from soil) showed slight pathogenicity to all test plants and isolate (B — from cotton seedlings) was highly destructive to cotton and pea.
Rhizoctonia
Pythium
Pythium ultimum
Root rot
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The depression of tea plants which principally due to root rot and some of them pro gress to death has been occurring in many tea cultivated areas in Japan. As the first step to reveal the causes of these disorders of tea plant, an evaluation of microbial factor as the causal agent of root rot was made.Isolation frequency of fungi from diseased tea roots (most of them was rootlet) was in order of Fusarium spp., Cylindrocarpon spp., and Pythium-like fungi. Rhizoctonia sp. and Verticillium sp. were also isolated occationally.More than 120 isolates of those fungi were tested their pathogenicity against the cut off tea rootlet in laboratory. Thirteen of the 15 Pythium, 15 of the 17 Cylindrocarpon, 15 of the 42 Fusarium, 4 of the 6 Rhizoctonia and 15 of the 40 isolates of unidentified fungi demonstrated moreor less pathogenicity. Isolates of Pythium, Cylindrocarpon and Fusarium which were found to have the strongest pathogenicities were heavy-innoculated to tea seedlings grown in pot.Each isolate also demonstrated pathogenicity in the experiments and Pythium (P-4) was the strongest.From these results, it was estimated that the microbial factor could be pointed out as a cause of the root rot and might be partially account for the root rots actually occurring in tea fields.Though fungal colony and morphology of mycelium of Pythium-like fungi were characteristics of Pythiutn species, the organ such as zoospore or zoo sporangium was not found and the fungi remained unidentified. MostCylindrocarpon isolates were thought to belong to C. radicicola and a Fusariunt isolate which showed the strongest pathogenicity to F. solani.
Pythium
Rhizoctonia
Root rot
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Pythium
Rhizoctonia
Root rot
Pythium ultimum
Damping off
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T wenty three isolates of Trichoderma spp.were isolated from rhizospheric soil of different plants in different regions of Egypt.By using dual culture method, they were tested for antagonistic Efficiency against tested phytopathogenic fungi (Rhizoctoniasoloni and pythiumultimum)The results revealed that Trichoderma atroviride and Trichoderma koningi icauses completely overgrowth (100%) on tested pathogenic fungi.Analysis of filtrated of Trichoderma atroviride contain of antibiotics Trichorzins(13.0mg/ml)But in case of Trichoderma koningii contain high amount of protease enzymes (6.34 m/mg protein).The results of this study identify Trichoderma atroviride and Trichoderma konigiv have a significant antagonistic effect against root rot Phytopathogen fungi and as promising biological control agents for further test against root rot disease.
Pythium ultimum
Rhizoctonia
Root rot
Pythium
Damping off
Trichoderma
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The influences of Gaeumannomyces graminis var. tritici (which causes take-all of wheat), Rhizoctonia solani AG-8 (which causes rhizoctonia root rot of wheat), Pythium irregulare, P. aristosporum , and P. ultimum var. sporangiiferum (which cause pythium root rot of wheat) on the population dynamics of Pseudomonas fluorescens 2-79 and Q72a-80 (bicontrol strains active against take-all and pythium root rot of wheat, respectively) in the wheat rhizosphere were examined. Root infection by either G. graminis var. tritici or R. solani resulted in populations of both bacterial strains that were equal to or significantly larger than their respective populations maintained on roots in the absence of these pathogens. In contrast, the population of strain 2-79 was significantly smaller on roots in the presence of any of the three Pythium species than on noninfected roots and was often below the limits of detection (50 CFU/cm of root) on Pythium -infected roots after 40 days of plant growth. In the presence of either P. aristosporum or P. ultimum var. sporangiiferum , the decline in the population of Q72a-80 was similar to that observed on noninfected roots; however, the population of this strain declined more rapidly on roots infected by P. irregulare than on noninfected roots. Application of metalaxyl (which is selectively inhibitory to Pythium spp.) to soil naturally infestated with Pythium spp. resulted in significantly larger rhizosphere populations of the introduced bacteria over time than on plants grown in the same soil without metalaxyl. It is apparent that root infections by fungal pathogens may either enhance or depress the population of fluorescent pseudomonads introduced for their control, with different strains of pseudomonads reacting differentially to different genera and species of the root pathogens.
Pythium ultimum
Pythium
Rhizoctonia
Root rot
Metalaxyl
Pseudomonas fluorescens
Take-all
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SUMMARY Many fungi were isolated from diseased coniferous seedlings at various localities in South Africa. At least 9 species have not previously been isolated from conifers and some species are new records for South Africa. Based on occurrence rates and pathogenicity tests the most important fungi taking part in early damping-off were species of Fusarium, Pythium and Rhizoctonia. In late damping-off or root rot a wide variety of fungi appeared to be involved. Here Fusarium oxysporum and Cylindrocarpon destructans were the predominant pathogens followed by Rhizoctonia solani, Pythium ultimum, Diplodia pinea and Pythium debaryanum, in that order of frequency. Other virulent damping-off organisms viz. Phytophthora cinnamomi, Pythium irregulare, Macrophomina phaseolina, Fusarium moniliforme var. moniliforme. F. moniliforme var. subglutinans, Botrytis cinerea, Cylindrocladium scoparium and Fusarium. aquaeductuum var. medium occurred in seedlings of only a few nurseries.
Damping off
Pythium ultimum
Pythium
Rhizoctonia
Macrophomina phaseolina
Root rot
Fusarium solani
Pythium aphanidermatum
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Though Rwanda is among the highest common bean producers and consumers, this crop is still challenged by different factors including root rot diseases resulting in low yield potential. Root rot diseases can cause up to 100% of yield loss. Despite different soil borne pathogens causing bean root rot diseases; there is no recent literature that clearly documents the most aggressive ones affecting common beans in Rwanda. This study aimed at identifying the root rot pathogens affecting bean crop in Rwanda. A survey was conducted to collect bean samples showing root rot symptoms in 12 agro -ecological zones where bean crop is mostly grown. The selection of samples was based on the level of contamination and the purity of cultures. A total number of 132 samples were therefore selected and considered for further analysis. The pathogen isolation was done in Rubona at Rwanda Agriculture and Animal Resources Development Board (RAB) Biotechnology and Pathology laboratory. Structural characterization of soil borne pathogens was also carried out along with pathogenicity evaluation. The growth rate of identified pathogens were significantly different (P<0.001). Significant differences were observed among isolates inoculated on both plantlets and seeds (P<001). Four root rot diseases were identified and characterized including Rhizoctonia spp, Fusarium spp,Sclerotium spp and several Pythium spp. The four pathogens were mostly observed in Northern and Southern parts of Rwanda than East and Western parts of Rwanda. Morphological characterization showed that Fusarium spp, Rhizoctonia spp and Sclerotium spp were predominant than Pythium species. Fusarium spp was identified as the most predominant fungal pathogen while Sclerotium spp was the most virulent pathogen. The present study suggests bean root rot disease control program to reduce losses associated with these diseases especially the use of resistant varieties since the fungi are widespread and survive in soils for a long period of time.
Root rot
Pythium
Rhizoctonia
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The pea root diseases at different stages in Fujian Province were investigated. The results showed that the diseases were caused by complex pathogenic fungi belonged to Fusarium solani (Mart. ) Sacc. , Fusarium oxysporum Schlesht. , Rhizoctonia solani Kuhn. Pythium ultinum Trow. , Aphanomyces euteiches Drechs. , Thielaviopsis basicola (Berk, et Br. ) Ferr. and Fusarium spp. The results of inoculation and re-inoculation experiments proved the Fusarium solani (Mart. ) Sacc. and Aphanomyces euteiches Drechs. had a higher virulence than others.
Fusarium solani
Root rot
Pythium
Rhizoctonia
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Rhizoctonia
Bipolaris
Pythium
Root rot
Fungal pathogen
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