Thumbnail Image

Theses

Browse

2014 - 20182
Reset filters
Subject: Plant Pathology × Author: Dwivedi, Meenakshi ×
Reset filters

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    ThesisItemOpen Access
    Induction of mutation in Trichoderma strains for enhancing biocontrol potential and compatibility with fungicides
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2018-08) Dwivedi, Meenakshi; Vishunavat, K.
    Biocontrol serves as an effective alternate approach for plant disease management under changing food habits and commercialization of agriculture. Trichoderma has become one of the most successful fungal biocontrol agents (BCAs) in past few decades. The progress in achieving commercial, large-scale usage of biological pest control has been rather slow, major roadblocks being instability under diverse environmental conditions, questionable shelf-life and inconsistent performance, and limited compatibility with many fungicides commonly used in agriculture. BCAs need to be tolerant to chemicals which would be a prerequisite for their application in an integrated pest management (IPM) strategy and could be produced through induction of chemical and physical mutation in popularly used biocontrol species of Trichoderma. The present study was attempted to induce mutation by chemical (ethylmethane sulphonate, EMS) and physical (UV rays and _ rays) mutagens in two Trichoderma strains viz. T. asperellum (Th 14) and T. harzianum (Th 3), to develop mutants tolerant to the fungicides (thiophanate methyl and propiconazole) incompatible with the parent strains, that also possessed comparatively enhanced biocontrol potential. Mutants were developed to tolerate thiophanate methyl (up to 200μg ml-1) and propiconazole (up to 1000 μg ml-1). Mutants Th 3 M1 and Th M6 were found comparatively superior in rhizosphere competence in three crops viz. urd bean, mung bean and chilli. Upon evaluation of growth promoting potential in urd bean, mung bean and chilli, mutants Th 3 M1 (8067, 8600 and 11166 PVI), Th 3 M2 (7233, 7633 and 100500 PVI) and Th 3 M6 (7500, 8033 and 9966 PVI) were found significantly better. On the basis of production of indole acetic acid (IAA), mutants Th 3 M1 and Th 3 M6 were found significantly superior with 40.44 and 40.41 IU ml-1, respectively. The parent strains and all the mutants exhibited 100 per cent parasitisation of R. solani and M. phaseolina at 7 days after contact (DAC) and 12 DAC, respectively, whereas only mutants mutants Th 3 M1, Th 3 M3 and Th 3 M6 were able to completely parasitize F. oxysporum capsici at 15 DAC. Mutants Th 3 M1 and Th 3 M6 performed exceedingly well at 52°C with cfu count of 2.90 and 2.85 log10 cfu ml-1, respectively, as compared to the parent strains and other mutants. In quantitative assay for cellulase, mutants Th 3 M1 and Th 3 M6 were found superior with 163.00 and 123.00 IU ml-1 cellulase activity, respectively, as compared to the parent strains and other mutants. High cellualse activity of the mutants Th 3 M1 and Th 3 M6 could be correlated with their high rhizosphere competence potential. Quantitative assay revealed that mutants Th 3 M6 was best with 122.00 IU ml-1 chitinase activity, followed by Th 3 M1 (98.00 IU ml- 1) and Th 3 M3 (94.33 IU ml-1) as compared to the parent strain Th 3 (48.66 IU ml-1) and other mutants. Among all these secondary metabolites identified during analysis, the maximum peak area of chromatogram was covered by tributyl phosphate followed by benenamine, 2-methyl and quinoline. Their quantity was elevated in the mutants Th 3 M1 and Th 3 M6 as compared to parent strain Th 3. Hence, the present investigation highlighted that induction of mutation led to enhancement as well as diminution of biocontrol characteristics of Trichoderma strains (Th 14 and Th 3). Through chemical and physical mutagenesis, stable mutants Th 3 M1 and Th 3 M6 were obtained to tolerate high concentrations of fungicide propiconazole (1000 and 500μg ml-1). Mutants Th 3 M1 and Th 3 M6 were also found most promising in their performance in various parameters such as rhizosphere competence, growth promoting potential, mycoparasitic potential, conidial thermo-tolerance (upto 52°C), production of cellulase and chitinase enzymes and production of volatile secondary metabolites, as compared to parent strain Th 3. Mutants Th 3 M1 and Th 3 M6 could prove to be very crucial biocontrol component in integrated disease management strategies.
  • Thumbnail Image
    ThesisItemOpen Access
    Selection of growth promoting Trichoderma strains for crop improvement under sustainable agriculture
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2014-07) Dwivedi, Meenakshi; Tewari, A.K.
    Biocontrol is an important approach for plant disease management under changing food habits a and Trichoderma is an important component of these strategies and Trichoderma spp. can be found in locations that stretch the entire globe in a variety of soils and habitats. They are well recognized as biocontrol agents for soil borne plant pathogens and potential plant growth stimulators. In the present investigation Trichoderma were isolated from the soil samples collected from rhizosphere (RS) and rhizoplane (RP) of wheat (W), rice (R) and chickpea (C) from diseased fields. Based on visual differences in cultural characteristics different Trichoderma isolates isolated from their native crops were selected for further studies. Among 27 isolates (RS-18; RP-9) from wheat, 19 (RS-11; RP-8) were selected, 27 isolates (RS-17; RP-10) from rice, 16 (RS-9; RP-7) were selected and 24 isolates (RS-15; RP-9) from chickpea, 16 (RS-9; RP-7) were selected to study their efficacy on growth promoting effects in their native crops. Based on the performance on growth promoting effects in-vitro and in-vivo in their native crops i.e. wheat, rice and chickpea, 07, 06 and 06 promising Trichoderma isolates, , respectively were selected and further evaluated for their growth promoting effects in their native crops in-vitro and in-vivo. The results showed that 02 Trichoderma isolates from each crop viz. TRP-W8 & TRSW4 (wheat) , TRS-R8 & TRS-R4 (rice) and TRP-C4 & TRP-C3 (chickpea) were found significantly better than other isolates, standard check (Th-14) and check in promoting growth of their native crops. The selected Trichoderma isolates (02 no. from each crop) were further tested for their growth promoting potential on their native crops and vice-versa. In-vitro and in-vivo studies revealed that Trichoderma isolates from their native crops were found significantly superior in germination, plumule/shoot length & weight, radical/root length & weight and seedling/plant vigour index in their native crops as compared to other crops. Among these Trichoderma isolates TRP-W8 (wheat), TRS-R8 (rice) and TRP-C4 (chickpea) were found significantly best in germination and plant vigour index (3865.0 & 9919.68; 4115.0 & 6204.12 and 5303.0 & 5215.68) as compared to check (2807.0 & 7359.0; 3072.0 & 5200.0 and 3190.0 & 4060.3) in vitro and in vivo in their native crop viz. wheat, rice and chickpea, respectively. All the selected Trichoderma isolates (06 no.) were identified as Trichoderma viride (T. asperellum) with the help of Bio-Log system. In dual culture studies, all the 06 Trichoderma isolates (TRP-W8, TRS-W4, TRS-R8, TRSR4, TRP-C4 and TRP-C3) were found very effective in parasitizing (100%) the test pathogens viz. Sclerotinia sclerotiorum (chickpea), Rhizoctonia solani (chickpea and rice) and Bipolaris sorokiniana (wheat) within 7 days after contact. The present investigations revealed that crop native Trichoderma isolates are more efficient in increasing seed germination and plant vigour in their native crops as compared to other crops. Therefore, these crop native Trichoderma isolates could be better exploited in their native crops after testing their antagonistic potential against the plant pathogens for overall crop health and productivity under IDM /organic cultivation for sustainable agriculture.