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Subject: Plant Pathology × Author: Sharma, Krishan Kumar × Start date: 2004 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Morphological and molecular characterization of rhizospheric isolates of Trichoderma and determination of their biocontrol efficacy
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2009-09) Sharma, Krishan Kumar; Singh, U.S.
    The genus Trichoderma contains species that are of a great economic importance due to their ability to act as biological control agents against a large variety of fungal plant pathogens. In the present investigation thirty isolates of the Trichoderma sp. Were obtained from the rhizosphere soils of different plants at different locations at Nainital, Almora, Udham Singh Nagar, Derhadun, Haridwar and Tehri Garhwal districts of Uttarakhand (India). The isolates were characterized on the basis of their cultural, morphological, biochemical and molecular characteristics. The cultural characteristics included linear growth, colony colour, and pigmentation and growth pattern. Morphological characteristics studied were structure, shape and arrangement of conidiophores, phialides and conidia. Out of thirty isolates, 6 isolates namely PB10, PB13, PB23, PB26, PB27 and PB28 were identified as T. virens and remaining 24 isolates as T. harzianum. To estimate the genetic variation among 30 isolates of Trichoderma random amplified polymorphic DNA (RAPD) markers were used. A total number of 792 reproducible polymorphic bands were obtained using 13 random primers. The data were subjected to numerical analysis using NTSYS software and genetic distance between each isolate was calculated. Cluster analysis was used to generate a dendrogram showing the relationship among them. The isolates grouped into two major clusters, the first major cluster consisted of 6 isolates of T. virens (PB10, PB13, PB23, PB26, PB27 and PB28) and remaining 24 isolates of T. harzianum belonged to second major cluster. The similarity matrix indicated that PB 8 and 21 were genetically distinct as they showed only 1% similarity while the isolates PB 29 and 30 were genetically closer with 61% similarity. Further studies on hyphal and sclerotial colonization of fungal pathogens revealed that PB 2, PB 19 and PB 15 were most aggressive hyphal colonizer and inhibited hyphal growth of all three fungal pathogens i.e. R. solani, S. rolfsii and F. oxysporum. Out of 30, nineteen isolates colonized the sclerotia of R. solani, while seven isolates colonized the sclerotia of S. rolfsii. Five isolates were able to colonize sclerotia of both the pathogens. Isolate PB 16 was most aggressive sclerotial colonizer and colonized sclerotia of both R. solani and S. rolfsii. Most of the isolates were able to utilize both cellulose and chitin. Isolate PB 29 was most effective utilizer of both the susbstrates. All the isolates significantly suppressed sheath blight development 30 days after application as seed treatment. Isolate PB 22 was most efficient inducer of ISR. Different isolates exhibited differential ability to promote root and/or shhot growth in rice, tomato and mustard. Vermicompost was the best substrate for the multiplication of Trichoderma. Isolate PB23 showed tolerance to water stress and was able to colonize cow dung even at 5% moisture content. It enhances water stress tolerance of mustard seedlings when applied as seed treatment.
  • Thumbnail Image
    ThesisItemOpen Access
    Morphological and molecular characterization of rhizospheric isolates of Trichoderma and determination of their biocontrol efficacy
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2009-09) Sharma, Krishan Kumar; Singh, U.S.
    The genus Trichoderma contains species that are of a great economic importance due to their ability to act as biological control agents against a large variety of fungal plant pathogens. In the present investigation thirty isolates of the Trichoderma sp. Were obtained from the rhizosphere soils of different plants at different locations at Nainital, Almora, Udham Singh Nagar, Derhadun, Haridwar and Tehri Garhwal districts of Uttarakhand (India). The isolates were characterized on the basis of their cultural, morphological, biochemical and molecular characteristics. The cultural characteristics included linear growth, colony colour, and pigmentation and growth pattern. Morphological characteristics studied were structure, shape and arrangement of conidiophores, phialides and conidia. Out of thirty isolates, 6 isolates namely PB10, PB13, PB23, PB26, PB27 and PB28 were identified as T. virens and remaining 24 isolates as T. harzianum. To estimate the genetic variation among 30 isolates of Trichoderma random amplified polymorphic DNA (RAPD) markers were used. A total number of 792 reproducible polymorphic bands were obtained using 13 random primers. The data were subjected to numerical analysis using NTSYS software and genetic distance between each isolate was calculated. Cluster analysis was used to generate a dendrogram showing the relationship among them. The isolates grouped into two major clusters, the first major cluster consisted of 6 isolates of T. virens (PB10, PB13, PB23, PB26, PB27 and PB28) and remaining 24 isolates of T. harzianum belonged to second major cluster. The similarity matrix indicated that PB 8 and 21 were genetically distinct as they showed only 1% similarity while the isolates PB 29 and 30 were genetically closer with 61% similarity. Further studies on hyphal and sclerotial colonization of fungal pathogens revealed that PB 2, PB 19 and PB 15 were most aggressive hyphal colonizer and inhibited hyphal growth of all three fungal pathogens i.e. R. solani, S. rolfsii and F. oxysporum. Out of 30, nineteen isolates colonized the sclerotia of R. solani, while seven isolates colonized the sclerotia of S. rolfsii. Five isolates were able to colonize sclerotia of both the pathogens. Isolate PB 16 was most aggressive sclerotial colonizer and colonized sclerotia of both R. solani and S. rolfsii. Most of the isolates were able to utilize both cellulose and chitin. Isolate PB 29 was most effective utilizer of both the susbstrates. All the isolates significantly suppressed sheath blight development 30 days after application as seed treatment. Isolate PB 22 was most efficient inducer of ISR. Different isolates exhibited differential ability to promote root and/or shhot growth in rice, tomato and mustard. Vermicompost was the best substrate for the multiplication of Trichoderma. Isolate PB23 showed tolerance to water stress and was able to colonize cow dung even at 5% moisture content. It enhances water stress tolerance of mustard seedlings when applied as seed treatment.