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Influence of Ph on Growth and Sclerotia Formation of Sclerotium Rolfsii Causal Agent of Foot Rot Disease of Betel Vine.

B. C. Sarker
Lecturer
Agrotechnology Discipline, Khulna University, Khulna

S. K. Adhikary
Professor
Agrotechnology Discipline, Khulna University, Khulna

S. Sultana
Assistant Professor
Agrotechnology Discipline, Khulna University

A. Biswas
Scientific Officer
Salinity Management and Research Center, SRDI, Batiaghata, Khulna

S. F. D. Azad
PhD Student
Agrotechnology Discipline, Khulna University, Khulna

Abstract/ Executive Summary:

An experiment was conducted to evaluate the effect of different pH levels (4.5, 4.0, 5.5, 6.0, 6.5, 7.0, 7.5 and 8.0) on radial growth, and formation of sclerotia, weight of sclerotia of Sclerotium rolfsii on PDA (Potato Dextrose Agar) medium and fresh weight and dry weight of S. rolfsii on PDB (Potato Dextrose Broth) medium. Radial growth, fresh weight and dry weight, at different pH levels differed significantly at 1% level of significance but number of sclerotia formation and their weight did not differ. Optimum pH for radial growth, fresh weight and dry weight were found 5.0 to 6.0, 4.5 to 6.5 and 4.5 to 6.5, respectively.

Keywords: pH, Sclerotium rolfsii, Betel Vine

Location: Digholia Upazila of Khulna District.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Betel leaf, Diseases

Objectives:

The disease caused by Sclerotium rolfsii commonly known as seedling blight, foot rot, collar rot and Southern blight of many crops (Talukder, 1974; Chowdhury, 1946; Ahmed, 1986). Sclerotium rolfsii initiate infection usually at the collar region of the susceptible host (Punja and Grogan, 198). The mycelial growth and sclerotia production of this fungus is influenced by many factors including pH, temperature, individual nutrients and volatile compounds like ethanol and C/N ratio.

Methodology:

Stems of Chachi variety of betel vine showing typical symptoms of Sclerotium rolfsii was collected from Digholia Upazila of Khulna District. The fungus was isolated following standard procedures (Dhingra and Sinclair, 1985). Diseased stems were thoroughly washed under running tap water. The stems were cut into convenient size (about 1 cm) containing black lesion where healthy and diseased tissue remains together. The cut stem pieces were first thoroughly washed by sterilized distilled water and then transferred to 0.1% sodium hypochloride (NaOCl) solution and kept there for 5 minutes. Surface sterilized stem pieces were transferred on sterilized blotting paper to remove excess NaOCl solution. The cut pieces were then placed onto sterilized water agar in glass petriplates with the help of sterilized forceps and incubated in room temperature (30±2)⁰C until mycelial formation. All the works were done in a laminar airflow cabinet. Fungal isolates was identified based on the characteristics of hyphae and sclerotia (Lilly and Barnett, 1951).

Pathogenicity test was done on excised stem of betel vine. Healthy stems of betel vine were cut into pieces (about 1 inch.) and surface sterilized with 70% ethanol for 10 seconds. Stem pieces were injured softly by flame sterilized pointed needles and then placed onto sterilized water agar. Advance hyphae were cut from 30 hours old pure cultures aseptically with the help of cork borer and then placed at three plates (both ends and centre) onto the stems (Dhingra and Sinclair, 1985).

Eight different pH levels namely 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 and 8.0 were taken as treatments. Hundred (100) ml PDA was taken on 250 ml conical flask. Different pH were adjusted by adding either 0.1N HCl or 0.1N NaOH and measured by pH meter. Advance hyphae of 32 hours old culture grown on PDA at pH 6.0 were cut by flame sterilized 5 mm cork borer. The inoculated petriplates were kept in the growth chamber at a temperature of 26±2⁰C for 54 hours. Radial growth of the isolates was measured by averaging the diameters taken for each colony and then these plates were kept there for 30 days for sclerotia formation. After 30 days the sclerotia of each petriplates were separated by using camel hair brush and the number of sclerotia of each petriplates was counted manually. The weight of sclerotia of each plate was measured by using an electrical balance.

For the measurement of fresh weight and dry weight of the fungus Sclerotium rolfsii was grown on Potato Dextrose Broth (PDB). Hundred (100) ml PDB was taken in each 250 ml conical flask. The pH of the PDB was adjusted to 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 and 8.0 by adding either 0.1N HCl or 0.1N NaOH where needed. The PDB was inoculated by 5 mm mycelial block, one for each, taken from 32 hours culture grown on PDA. The inoculated conical flask was kept in the growth chamber at a temperature of 26±2⁰C for 7 days. After incubation the fungal mass in each conical flask was separated by filtration using Whatman paper no. 1. The filtrates were discarded and fungal mass on blotting paper was kept in the laboratory at room temperature for 40 hours for air drying. Then fresh weight was measured by using electrical balance. The fungal mass of all treatments were then oven dried at a temperature of 70⁰C for 72 hours. Then the oven dried fungal mass were weighted to have dry weight.

Source of Information: IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS) e-ISSN: 2319-2380, p-ISSN: 2319-2372.Volume 4, Issue 1 (Jul. - Aug. 2013), PP 67-70 www.iosrjournals.org

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Achievement/Findings:

Sclerotium rolfsii identified from the naturally infected samples of foot rot of betel vine. pH 5.5 was more effective for radial growth of Sclerotium rolfsii and less at pH 5.0. pH 5.0 was more effective for sclerotia formation of Sclerotium rolfsii and less at pH 5.5. pH 4.5 was more effective for weight of formed sclerotia of Sclerotium rolfsii and less at pH 5.5 Fresh weight and dry weight was found high at 5.5 pH level and low at pH 7.5. All the highest radial growth, fresh weight and dry weight were found at pH 5.5, which indicate that there is a consistency among the parameter studied.

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