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Survival of Bipolaris Sorokiniana (sacc.) Shoemaker in Soil and Residue of Wheat

P.K. MALAKER*
Wheat Research Centre, Nashipur, Dinajpur-5200, Bangladesh

I.H. MIAN
Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1703, Bangladesh.

MD. MANIRUZZAMAN KHANDAKER
Department of Botany, Government Saadat College, Tangail-1900, Bangladesh.

M.M.A. REZA
Wheat Research Centre, Nashipur, Dinajpur-5200, Bangladesh

Abstract/ Executive Summary:

Off-season survival of Bipolaris sorokiniana (Sacc.) Shoemaker in sterilized and unsterilized soils, and in residues of wheat spread on soil surface were determined. Population of viable propagules of the fungus per gram of soil or residue was determined at monthly interval using dilution plate technique. It was found that the population of B. sorokiniana increased initially for two months in both soils and residues and declined thereafter. The decline was very sharp up to four months of survival and then onwards a gradual decline was observed. In case of free residue, a gradual decline in population was observed from the beginning of the pathogen survival. The pathogen could be recovered up to eight and ten months from the unsterilized and sterilized soil, respectively. It was not possible to recover the pathogen from the residues in unsterilized and sterilized soil after seven and eight months. The pathogen could survive for 12 months in free residue stored at room temperature.

Keywords: Bipolaris sorokiniana, Survival, Soil, Residue, Wheat

Location: Bangabandhu Sheikh Mujibur Rahman Agricultural University campus, Gazipur

Start Date: 00-03-2000

End Date:

Program Area: Pest Management

Commodity: Diseases

Objectives:

To determine the population of viable propagules of B. sorokiniana and the extent of its off-season survival in soil and crop residues of wheat.

Methodology:

Residues of wheat (cv. Kanchan) infected by B. sorokiniana were collected from the field after harvest in March, 2000. The residues were cut into 5 cm pieces and air-dried under shade for two days. Five kilograms of dried residues were then thoroughly mixed with upper 5 cm of soil in each of two 1×3 m beds in Bangabandhu Sheikh Mujibur Rahman Agricultural University campus, Gazipur. The residues were also evenly spread on the surface of the soil. The soil was silty loam and no manures or fertilizers were used. One of the beds was kept unsterilized and the other was sterilized with 2% formalin solution, 15 days before mixing the residues with soil. Samples of air-dried residues were also stored as free residue in brown paper bags at room temperature. Soil samples were collected from the infested beds at monthly interval beginning from April 2000. Ten sub-samples were collected from each bed at 0-5 cm depth using an auger. The subsamples were intermixed into a composite sample separately for sterilized and unsterilized soils. The composite samples were dried under shade, pulverized and screened through 20-mesh sieve to remove large particles and debris. Soil suspension of desired dilution was prepared with 10 g sample in 0.1% water agar at 45^?C. A 1 ml aliquot was then pipetted into each Petri plate (9 cm) containing a selective medium (Reis 1983), and spread uniformly over the surface of the medium by gently tilting the plate. Compositions of the selective medium were: 35 g sliced potato, 5 g sucrose, 15 g agar, 5000 µg streptomycin and 250 µg benomyl in 1000 ml distilled water. Eight plates were used for each soil sample and were incubated for 5 days at 25 ± 2ºC under 12/12 hr light and darkness period. After the incubation period, the colonies of B. sorokiniana were counted under a dissecting microscope and the number of propagules per gram of soil was determined by multiplying the plate count with the dilution factor (Reis 1983). During the sampling period from April to November, a 1:200 dilution was used while 1:100 dilution was used for rest of the sampling period. Samples of infected residues were also drawn randomly from each treatment at monthly interval, chopped into 2-3 cm pieces and intermixed into composite sample. A 5 g composite sample was taken in a stoppered flask containing 100 ml of water and two drops of Tween-20 and shaken vigorously for 10 minutes after adding. Ten ml of this suspension was poured into 90 ml of water and stirred for 5 minutes. A 1 ml aliquot was then spread over the surface of the selective medium in each of eight plates and incubated at 25 ± 2⁰C under 12/12 hr light and dark cycle. After five days of incubation, the colonies of B. sorokiniana were counted and the number of propagules per gram of residue was determined.

Source of Information: Bangladesh J. Bot. 36(2): 133-137, 2007 (December)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The population of the fungus increased in the soil for the first two months of survival, especially when crop residue was added. The decline in population after two months and its disappearance after 8-10 months might be owing to exhaustion of organic matter in soil. Antagonistic organisms against B. sorokiniana might also play an active role to reduce population and survival period of the fungus.

Knowledge Management: Journal