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Detection of the Causal Agent of Rice Seedling Blight

Dr. T H Ansari
Principal Scientific Officer
Plant Pathology Division,Bangladesh Rice Research Institute,Gazipur-1701, Bangladesh

M Ahmed
Scientific Officer
Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

Abstract/ Executive Summary:

An investigation was carried out to know the causal agent(s) of rice seedling blight occurred in the trays and field. The pathogen was isolated both from the soil and infected seedlings. The infected samples of rice seedling blight were collected from Gopalganj (Tungipara), Rajshahi and Gazipur during boro season. Fungi were isolated from the infected stem at the base of diseased seedlings collected from both trays and fields of different districts. The fungi were cultured on PDA media. After 15 days plates were flooded with sterile water and scraped with a sterile spatula. The resulting suspensions were used for seedling inoculation. Before inoculation, rice seeds were treated with hot water for 15 min at 60⁰C to remove any surface contaminants. Seeds were sown in plastic trays containing sterilized soil. After 7 days of seeding fungal suspension was inoculated at the base of seedling in the tray soil. Preliminary evaluation of symptoms was performed 7 days after inoculation. Further isolation of the fungi was also done to confirm the causal agent.The isolates grown on PDA produced white and light pinkish color of the mycelia. Pigments in the media were observed as yellowish, reddish brown and pink color with or without concentric rings. Preliminary observation on the morphological characteristics of the fungi isolated from different seed bed and trays indicated that the causal agent of seedling blight was Fusarium. Mycelia were hyaline in color and septate. Conidia were also hyaline in color. Different types of micro and macro conidia were observed under compound microscopic studies. Micro conidia were ovate, oval and 1-2 celled. Macro conidia were almost straight or slightly curved 2-3 septate, foot-cells was identified. From the morphological and microscopic studies it was confirmed that all the tested samples were infected with Fusarium spp. This is the first report of Fusarium seedling blight of rice in Bangladesh. Further studies will be conducted intensively using molecular tools.

Keywords: Rice, Causal agent, Seedling blight, Disease

Location: BRRI Gazipur and Rajshahi

Start Date: 01-07-2014

End Date: 30-06-2015

Program Area: Pest Management

Commodity: Rice

Objectives:

To know the causal agent(s) of rice seedling blight occurred in the trays and field.

Methodology:

The pathogen was isolated both from the soil and infected seedlings. The infected samples of rice seedling blight were collected from Gopalganj (Tungipara), Rajshahi and Gazipur during boro season. Fungi were isolated from the infected stem at the base of diseased seedlings collected from both trays and fields of different districts. Tissues were washed under running tap water, sterilized with 1% NaOCl for 30 seconds, rinsed twice in sterile distilled water, placed in Petri plates containing Potato Dextrose Agar (PDA) medium and kept at room temperature. After 4 days, mycelia grown from tissues were transferred to fresh Petri dishes containing potato dextrose agar (PDA). White growth of the fungi in the soil level at plant base or soil sub-level (just below soil surface at the root zone of infected rice seedling) was detected. The fungi were isolated using the needle and then placed in the PDA media. The fungi were transferred again into a fresh petridish containing PDA media. The isolated fungi were sub-cultured in PDA at room temperature. After 15 days plates were flooded with sterile water and scraped with a sterile spatula. The resulting suspensions were used for seedling inoculation. Before inoculation, rice seeds were treated with hot water for 15 min at 60⁰C to remove any surface contaminants. Seeds were sown in plastic trays containing sterilized soil. After 7 days of seeding fungal suspension was inoculated at the base of seedling in the tray soil. Preliminary evaluation of symptoms was performed 7 days after inoculation. Further isolation of the fungi was also done to confirm the causal agent.

Source of Information: BRRI Annual Report 2014-15.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From the morphological and microscopic studies it was confirmed that all the tested samples were infected with Fusarium spp. This is the first report of Fusarium seedling blight of rice in Bangladesh. Further studies will be conducted intensively using molecular tools.

Knowledge Management: Report/Proceedings