Md. Iqbal Ahmad
Agrotechnology Discipline, Khulna University, Khulna-9208, Bangladesh
Avijit Kumar Biswas
Agrotechnology Discipline, Khulna University, Khulna-9208, Bangladesh
Mst. Sabiha Sultana
Agrotechnology Discipline, Khulna University, Khulna-9208, Bangladesh
Bidhan Chandro Sarker
Agrotechnology Discipline, Khulna University, Khulna-9208, Bangladesh
Chhoa Mondal
Agrotechnology Discipline, Khulna University, Khulna-9208, Bangladesh
Sclerotium oryzae, Carbon source, Nitrogen source, pH, Different media, Rice
Plant Breeding and Biotechnology Laboratory, Agrotechnology Discipline, Khulna University, Khulna, Bangladesh.
Pest Management
Diseases, Rice
A typical symptom of sheath rot disease was collected from the greenhouse of Plant Breeding and Biotechnology Laboratory, Agrotechnology Discipline, Khulna University, Khulna, Bangladesh. The fungus was isolated following standard procedures of Dhingra and Sinclair (1985). To obtain a pure culture of S. oryzae, a hyphal tip from water agar was transferred aseptically to PDA petridish by using a sterile fine needle and then incubated at a temperature of 25±20C for 52 hours. Advanced hyphae were transferred aseptically into the test tube slant containing PDA with pH 6.5 and incubated at room temperature (25±2 0C) for 52 hours. After incubation, these slants were carefully checked for contamination and then preserved at 4 0C in a refrigerator for further use. Fungal isolates were identified based on the characteristics of hyphae and sclerotia (Lilly and Barnett, 1951). A pathogenicity test was done on excised rice stem with sheath. The healthy stem of rice was cut into pieces (about 1 inch) and surface sterilized with 70% ethanol for 10 seconds. After that cut pieces were placed on sterilized blotting paper for the removal of excess ethanol present in the stem. Stem pieces were injured softly by flame sterilized pointed needles and then placed onto sterilized water agar. Advanced hyphae were cut from 30 hours old pure cultures aseptically with the help of a cork borer and then placed at three injured places (both ends and center) onto the stems (Dhingra and Sinclair, 1985). Then typical sheath rot symptoms were observed on sheath and re-isolation was done following the protocol of Dhingra and Sinclair, 1985. The various media composition (g L-1) shown below were tested. PDA was prepared following the standard procedure (Anonymous, 1968). Potato 200 g, dextrose 20 g, agar 15 g, distilled water 1L. 20 g rice stem/betel vine stem was taken and pasted with the help of mortar-pestle by adding 5 ml distilled water for preparing the paste. After that 995 ml, distilled water was added slowly into the paste. It was then sieved into a beaker; 20 g dextrose and 15 g agar were added with it. 20 g cornmeal extract, 20 g dextrose, 15 g agar, 1L distilled water. 2 g NaNO3, 1 g K2HPO4, 0.5 g MgSO4, 0.5 g KCl, 0.01 g FeSO4, 30 g Sucrose, and 15 g agar,1L distilled water. Glucose (13.5 g L-1), Sucrose (12.5 g L-1), and Starch (12.5 g L-1) were tried individually as a constitute of carbon source in Czapek dox Agar medium. Three carbon compounds viz; Peptone (2.5 g L-1), Sodium nitrate (8.5 g L-1), and potassium nitrate (10 g L-1) were tried individually as a constitute of nitrogen source in Czapek dox agar medium. Five different pH levels namely 5.0, 6.0, 7.0, 8.0 and 9.0 were taken as treatments. Hundred (100) ml PDA was taken in a 250 ml conical flask. Different pH was adjusted by adding either 0.1N HCl or 0.1N NaOH and measured by pH meter. All the media were sterilized at 1210C temperature, 15 PSI for 15 min. After cooling, the media were poured into 90 mm Petri dishes. All these treatments were replicated into five plates. Advanced hyphae of 3 days old culture were used for inoculation. A 5 mm block of the mycelium was cut with flame sterilized cork borer (5 mm). The mycelial blocks were taken from the edge of the colony. Each mycelial block was placed upside down at the center of each petridish. All these operations were done under aseptic conditions. The inoculated petridishes were kept in the growth chamber at (25±2 0C) until the mycelia touch the edge of petridishes. Mycelial growth of the isolates was measured by averaging the two dimensions (90 mm petridish) taken for each colony after six days of inoculation for different growth media, carbon source, nitrogen source, and three days for pH. The experiment was laid out under a completely randomized design (CRD) with three replications. The data were analyzed statistically using STAR (statistical tools for agricultural research) program, version-02, IRRI, Los Baños, Philippines computer program.
South Asian J. Agric. Vol. 7, No. 1&2, 2016-’19 : 67-72
Journal