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Variations in Different Isolates of Rhizoctonia Solani Based on Temperature and Ph

B. K. GOSWAMI
Principal Scientific Officer
Plant Pathology Division, RARS, BARI, Jamalpur

M. M. RAHAMAN
Scientific Officer
Plant Pathology Division, RARS,BARI, Jamalpur

A. K M. A. HOQUE
Research Student
Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur,

K. BHUYAN
Professor
BSMRAU, Gazipur, Bangladesh.

I. H. MIAN
Professor
BSMRAU, Gazipur, Bangladesh.

Abstract/ Executive Summary:

An experiment was conducted to find out variation in isolated Rhizoctonia solani based on radial mycelial growth and sclerotial production. Five isolates of Rhizoctonia solani representing five clusters group were selected and were grown at different levels of temperature and pH on potato dextrose agar (PDA). It was observed that optimum temperature and pH for growth and sclerotial production varied among the isolates. The rates of growth and sclerotial formation were not uniform at the same levels of the two growth factors. The maximum mycelial growth of all isolates was found at 30⁰C. At 35⁰C, only GAZ-9 and GAZ-18 showed initiation of growth, but the rate was very slow. The optimum temperature for sclerotial production of the isolates GAZ-9, JES- 16, GAZ-18 SYL-26 was 30⁰C and for the isolate DIN-8 was 25⁰C. The optimum pH for maximum radial growth was 6 for DIN-8 and 7 for other four isolates. The maximum number of sclerotia was produced by DIN-8, GAZ-9, and SYL-30 at pH 8, 4, and 7, respectively. The optimum pH for sclerotia formation in JES-16 and GAZ-18 was pH 6.

Keywords: Rhizoctonia solani, Variations, Temperature, pH

Location: BARI Gazipur

Start Date:

End Date:

Program Area: Pest Management

Commodity: Diseases

Objectives:

To find out variations in different isolates of R. Solani based on different temperature and pH regimes on culture media

Methodology:

A study was undertaken to find out the variations among the isolates of R. solani on the basis of mycelial growth and scierotium formation at different temperature and pH levels. Isolates of R. solani were collected from different diseased plant parts and soils from 22 districts of Bangladesh. For isolation and identification, standard procedures were followed as described by Bhuiyan (1994). After identification, the isolates were designated using first three letters of the district from where they were collected and serial numbers were given in accordance with the date of collection. Altogether 50 isolates were collected and stored in test tube slant at 10°C. The collected isolates were grown on PDA in 9 cm diameter Petri dishes with four replications and incubated for 4 weeks at 25±1°C. Observation was made regularly and data on the myccelial growth rate/24 hour, structure, zonation, and colour of the colony, number of sclerotia/cm2 , colour of scierotia, shape and size of sclerotia, days to scierotial initiation and the formation patterns of scierotia were collected. Variations among the isolates based on morphological characters was analyzed following cluster analysis for classifying 50 isolates into more or less homogeneous groups. The collected isolates were classified into five cluster group. Finally five isolates, namely DIN-8, GAZ-9, JES-16, GAZ-18 and SYL- 30 were selected from five different cluster groups to find out the variations at different levels of temperature and pH. Five levels of temperatures viz. 15, 20, 25, 30, 35 °C were maintained in the trial. Fifteen milliliter of PDA was dispensed into each of the Petri dish (9 cm diameter). The pH of the medium was adjusted at 6.5. Mycelial discs of 4 mm diameter were cut aseptically with flame sterilized cork borer from the margin of 2 days old culture of five different R. solani isolates. One disc was placed in the center of individual Petri dish. Four dishes were used for each isolates. After inoculation, the petridishes were incubated in incubators maintaining the five different temperature levels. The petridishes were arranged in the incubators following completely randomized design (CRD). Five different levels of pH viz. 4.0, 5.0, 6.0, 7.0, and 8.0 were maintained to study the isolates variation at different pH. The pH level was adjusted by adding HCI or NaOH before solidifying the PDA media with continuous stirring. Procedure for pouring of PDA media and inoculation of mycelial discs with five different isolates were same as mentioned before. After inoculation, the Petri dishes were incubated at 25°C. Four dishes were used for treatment. The Petri dishes were arranged in the incubators following CRD. From both the trials of temperature and pH, the data on radial colony growth and number of sclerotia/cm² of the colony were recorded. Radial colony growth was measured by averaging the two diameters taken at right angles for each colony when mycelial growth of some isolates reached the edge of the Petri plates. Number of sclerotia of the colony was recorded by averaging the data of three different area of a Petri dish after two weeks of incubation. Data were analyzed statistically using MSTAT-C computer programme and means were compared using DMRT.

Source of Information: Bangladesh J. Agril. Res. 36(3) : 389-396, September 2011, ISSN 0258-7122

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The rates of growth and sclerotial formation were not uniform at the same levels of the two growth factors. The maximum mycelial growth of all isolates was found at 30⁰C. At 35⁰C, only GAZ-9 and GAZ-18 showed initiation of growth, but the rate was very slow. The optimum temperature for sclerotial production of the isolates GAZ-9, JES- 16, GAZ-18 SYL-26 was 30⁰C and for the isolate DIN-8 was 25⁰C. The optimum pH for maximum radial growth was 6 for DIN-8 and 7 for other four isolates. The maximum number of sclerotia was produced by DIN-8, GAZ-9, and SYL-30 at pH 8, 4, and 7, respectively. The optimum pH for sclerotia formation in JES-16 and GAZ-18 was pH 6.

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