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Efficacy of Some Probiotic Rhizosphere Bacteria Against Seed Borne Fungi of BRRI Dhan46

E. Nahar
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh.

N. Sultana
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh

M.R. Islam
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh

M.Z.R. Bhuiyan
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh

Abstract/ Executive Summary:

We investigated the prevalence of seed borne fungal pathogens in rice variety BRRI Dhan46 and to evaluate the efficacy of antagonistic bacteria in controlling seed borne disease. A composite sample of BRRI Dhan46 was assayed. Five seed borne fungi viz. Fusarium sp. , Bipolaris oryzae, Curvularia sp. , Gliocladium sp. and Aspergillus flavus were isolated from the rice seeds. Fifteen probable antagonistic bacterial isolates were isolated from rhizosphere soil and screening was done to detect the most suitable antagonistic bacterial isolates against seed borne fungi of rice. Seeds of rice variety, BRRI Dhan 46 yielded 21.5% Fusarium sp., 6.25% Bipolaris oryzae, 4.75% Curvularia sp., 0.25% Gliocliodium sp. and 3.5% Aspergillus flavus infection in blotter method. Among fifteen isolates six isolates (Iso-1, Iso-2, Iso-3, Iso-5, Iso-7 and Iso-10) were found to be effective in dual culture method. In dual culture method, the bacterial Iso-2 produced higher inhibition of mycelia. Bacterial antagonist Iso-2 performed better than other isolates on seed borne fungal prevalence in blotter method. Seed treated with Iso-2 completely controlled seed borne Bipolaris oryzae, Aspergillus flavus and Gliocladium sp. The highest seed germination (98%) was recorded in seeds treated with Iso-2 and Iso-1. In water agar test tube method, the highest germination (96.67%) was found in Iso-2 treated seed. Iso-2 treated seed gave the highest Vigor Index (1424) and the lowest vigor index was noted (753) in untreated control in rolled paper towel method.

Keywords: Fungal diseases, Aspergillus, Bipolaris oryzae, Seed Borne Fungi, Probiotics

Location: Department of Plant Pathology, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka

Start Date:

End Date:

Program Area: Pest Management

Commodity: Fungicide

Objectives:

To determine the efficacy of antagonistic bacteria against seed borne fungal pathogens of rice.

Methodology:

The experiments were conducted in the Plant Disease Diagnostic Laboratory and Seed Pathology Laboratory of Department of Plant Pathology of Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh. Seeds of rice variety BRRI dhan46 were collected from Bangladesh Rice Research Institute (BRRI), Joydebpur, Gazipur. A composite sample of rice variety BRRI d han46 was assayed for the presence of seed borne fungi by Standard Blotter method. Number of germinated seeds was recorded along with the seed-borne fungi after 7-10 days of incubation. The results were expressed in percentage. For isolation of seed borne fungi from incubated seeds a bit of mycelium with spores were taken with the help of a sterile needle and transferred on PDA plates. Purification of seed borne fungal pathogens of rice was done by re-culture. Probable antagonistic Bacteria were isolated from rhizosphere soil following dilution plate method on nutrient agar plates. Then plates were kept in an incubator nutrient agar plates. Then plates were kept in an incubator antagonism against seed borne fungi was carried out in vitro. Twenty bacterial strains were isolated from rhizosphere soil of rice field and were tested by dual culture method. After incubation bacteria appeared with various types of colony with different size shape and colors. Then the bacterial colonies were selected and isolated depending on their colony color and streaked on new Nutrient Agar medium (NA) plates, separately. Purification was done by re-streaking on NA plates from single colony. Then stock culture of each strain was made on NA slants and kept at refrigeration for future use. In-vitro bio-assay of bacteria was done to cheek antagonistic activity of isolated bacteria following dual culture method. For morphological characters, colony color and surface textures were carefully studied and recorded as bacteria developed after 24 hours of incubation in NA medium. The isolated bacteria were prepared by sub-culturing on nutrient agar plate incubating at 30 C for 24 hours. Several biochemical tests were done following Bergey’s manual of determinative bacteriology such as gram reaction, oxidase test, catalase test, citrate utilization test, pectolytic test and gelatin liquefaction tests were performed.Blotter method was used to evaluate the effects of bacteria on seed germination and prevalence of seed borne fungi. Two hundred seeds of rice variety BRRI dhan46 were soaked in bacterial suspension (10⁹ cfu/ml) for 24 hours. Incase of control, seeds were soaked in sterile water. Treated seeds were evaluated following blotter method. Out of twenty, only six isolates were found effective against seed borne fungi. These, six isolates were used as seed treatments and one is untreated control. The treatments were T₁ = Isolate 1, T₂ = Isolate 2, T₃ = Isolate 3, T₄ = Isolate 5, T₅ = Isolate 7, T₆ = Isolate 10, T₇ =Control (without isolate). Seeds were treated with bacterial suspension containing 10 cfu /ml. Seeds were dipped in bacterial suspension for 2 hrs and then plated on moisten blotting paper. After that prevalence of seed borne fungi were determined. Treated seeds were placed on water agar test tube following the key of and data were recorded on % seed germination, number of normal seedlings, number of abnormal seedlings and number of dead seeds.Treated seeds were kept on rolled moisten paper towel following the key of [20] and data on length of shoot, length of root, % Germination and % seed infection were recorded. All the data were analyzed by using MSTAT-C computer package program and the mean separation was done by Duncan’s Multiple Range Test (DMRT) with 5% level of significance.

Source of Information: World Journal of Agricultural Sciences 12 (1): 49-56, 2016, ISSN 1817-3047

Article Link (Online Journal): DOI: 10.5829/idosi.wjas.2016.12.1.1901

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In this study it had been found that, untreated seeds resulted in poor germination and poor seedling vigor ,compared to antagonist treated seeds. The effect of antagonist as seed treatment could be attributed to unknown biological mechanisms since germination and vigor index were higher than no treated seeds. This could be due to the suppression of initial inoculum in seeds by seed soaking in bacterial suspension since the fungi were seed borne. Farmers might be advised to use seed treatment.

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