Jahnabi Bora ¹, B. C. Das ¹, K. Borkakoty ¹, P. K. Dutta ¹

Affiliations
1 Department of Plant Pathology, Assam Agricultural University, Jorhat 785013, Assam, IN

Abstract

Compost, biofertilizers and antagonists have been widely explored as effective and ecofriendly options for controlling plant diseases. An investigation was conducted to study in vitro growth and multiplication of talc-based Trichoderma harzianum and a commercial formulation of Trichoderma viride in different compost manures. Optimal compost and vermicompost supported excellent growth of both T. harzianum and T. viride, however, the efficacy of the mixed formulation of both optimal compost and vermicompost resulted in higher population of both the antagonists and they showed significant increase for up to 45 days after inoculation. Shelf life of both the antagonists was studied in vitro and in vivo over a period of 120 days. Higher population (cfu g⁻¹) was reported in optimal compost+vermicompost+T. harzianum, which was significantly higher than optimal compost+vermicompost +T. viride. The maximum population in vitro was recorded at 30 days of incubation, whereas it was recorded in 60 days of incubation in vivo.

Keywords

Biological Control, Management, Compost, Trichoderma harzianum, Trichoderma viride.

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Pranab Dutta ¹, B. C. Das ¹, M. Islam ²

Affiliations
1 Department of Plant Pathology, Assam Agricultural University, Jorhat, 785013, Assam, IN
2 Department of Life Sciences, Dibrugarh University, Dibrugarh, 786001, Assam, IN

Abstract

Sclerotinia rot caused by Sclerotinia sclerotiorum is a serious menace to the cultivation of french bean (Phaseolus vulgaris L.) in Assam. In vitro efficacy of antagonist by dual culture method was tested against S. sclerotiorum. Out of all the antagonists Pseudomonas fluorescens was found best causing growth reduction of 64.93 per cent followed by Bacillus snbtilis (62.86 %) and Trichoderma harzianum (59.08 %). Study on the mode of parasitism showed that the fungal antagonist initially caused coining and then lysed the pathogen hyphae and the bacterial antagonist ceased pathogen growth after coming in contact with the pathogen. Effect of fungal antagonist T. harzianum and bacterial antagonist's B. subtilis and P. fluorescens as seed treatment against Sclerotinia rot was evaluated under field conditions. Seed treatment with T. harzianum was found has most effective in improving seed germination (18.43%), reducing 90.46% infection and increasing yield (69.51%) over control plot. Efficacy of B. subtilis and P. fluorescence as seed treatment against the disease was next to T. harzianum treatment respectively.

Keywords

Antagonist, Biological Control, French Bean, Seed Treatment, Sclerotinia Rot.

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B. C. Das ¹, B. K. Das ¹, Pranab Dutta ¹, D. K. Sarmah ¹

Affiliations
1 Department of Plant Pathology, Assam Agricultural University, Jorhat, 785 013, Assam, IN

Abstract

In vitro osmoticant (manitol) amended and osmoticant free media of potato dextrose broth (PDB), modified Richard's broth (MRB) and Czapek dox broth (CDB) were tested for biomass production of Trichoderma harzianum Rifai. Osmoticant amended MRB was found best for production of maximum sporulation, cfu and dry weight of biomass of the antagonist, Osmoticant amended media produced higher biomass of T. harzianum than osmoticant free media. Growth and sporulation of T. harzianum was assessed in different carrier viz. starch, talc and molasses enriched charcoal powder (MECP) based formulation. Starch and MECP based formulation of T. harzianum showed increased trend in sporulation of the antagonist upto 60 days, but after this, viability of T. harzianum was abruptly decreased. Talc based formulation-exhibited gradual declining trend in multiplication and sporulation of T. harzianum after 30 days onwards. Among the nine formulation evaluated for growth and sporulation, starch based formulation alone performed best upto 60 days, followed by MECP based formulation. But after 60 days onwards, talc based formulation @ 3: 1 dose showed highest sporulation and maximum cfu, followed by starch formulation @ 1: 1 dose. The overall performance of talc-based formulation was better for growth and sporulation of the antagonist. Potentiality of T. harzianum as seed treatment with talc based T. harzianum and chemical were assessed field condition against Rhizoctonia solani causing stem rot disease of soybean. Lowest disease index and highest % seed germination was observed when seeds were treated with formulation of T. harzianum + talc + osmoticant formulation with enhanced plant vigour and yield of the crop.

Keywords

Biomass, Osmoticant, Rhizoctonia solani, Soybean, Stem Rot, Trichoderma harzianum.

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S. Mech ¹, B. C. Das ¹, D. K. Sarmah ¹

Affiliations
1 Assam Agricultural University, Jorhat 785013, Assam, IN

Abstract

In the present investigation, carbendazim tolerance in Trichorderma harzianum was induced by exposing the culture to UV radiation for different periods (viz. 0, 2, 4, 6 and 8 h) and then the same were grown in PDA amended with different concentration of carbendazim viz. 0.01, 0.05, 0.1 and 1.0 per cent, respectively. In each concentration, colonies developed after 5 days were isolated, purified with serial dilution and sub-cultured thrice on PDA without carbendazim and tested their stability. These resulted in the development of 18 stable mutants, which could tolerate up to 0,1 per cent of carbendazim while wild T. harzianum (Th-w) failed to tolerate the same. Based on radial growth of above 18 stable mutants grown on fungicide free PDA, only three stable mutants were selected, which were designed as Th-M₁, Th-M₂ and Th-M₃, In vitro antagonistic activities of these three mutants tested against Sclerotinia sclerotiorum, the causal agent of white mold of French bean on PDA showed maximum reduction of radial growth of pathogen by Th-M₂ In another test, all the mutants arrested sclerotial production of S. sclerotiorum, significantly. However, the mutant Th-M₂ showed maximum reduction when it was inoculated seven days prior to inoculation with S. sclerotiorum in MSM (4%) as compared to wild T. harzianum (Th-w).

Keywords

Carbendazim, Mutant, Sclerotinia sclerotiorum, T. harzianum, UV Radiation, White Mold.

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P. Datta ¹, B. C. Das ¹, D. K. Hazarika ¹

Affiliations
1 Department of Plant Pathology, Assam Agricultural University Jorhat 785 013, Assam, IN

Abstract

Combination of four different carriers along with Trichoderma harzianum as seed treatement was tested in pot condition against Rhizoctonia solani causing soybean stem rot. Conidial suspension (1 x 10⁸ conidia per ml) of the antagonist was used for seed treatment. Seed germination (%) and yield (g/plant) was found higher in all treatments irrespective of carrier and antagonist used. However, seed germination and yield was found to he on par. The higbest germination (85.33%) and yield (11.78 g/plant) and lowest disease index (1.5) were obtained when seeds were treated with T. harzianum + methylcellulose. Seed treatment with sub-lethal doses of thiram (0.05 and 0.01 %) and T. harzianum showed lower disease index, higher germination and yield than the lethal dose (0.3 %) alone.

Keywords

Carrier, Disease Index, Methylcellulose, Rhizoctonia solani, Thiram, Trichoderma harzianum.

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