Abstract:
The experiment was conducted for morphological characterization, molecular
identification and to study pathogenic variation among Rhizoctonia solani
isolates collected from different areas of Bangladesh. The experiment was
performed in the laboratory of Plant Pathology Division, Bangladesh Rice
Research Institute (BRRI), Gazipur during the period of June 2019 to February
2020. Eight isolates were isolated from seven different areas in Bangladesh and
all isolates showed wide morphological variation in terms of size of sclerotia
(1.62 mm to 4.38 mm), colony colour and texture of sclerotia ranging from
dark brown to light brown with rough to smooth in texture. Initiation of
sclerotia formation time was varied from 4 to 6 days. Based on the colony
pigmentation, all the isolates were assigned into 4 groups: dark brown, dirty
white, milky white and yellowish brown. All the isolates had growth rates
between 5.00-5.87cm² per day with an average of 5.33cm²/day. All the
isolates except RS-2 and RS-7 were confirmed as Rhizoctonia solani with the
molecular identification using the primer pair ITS1/ITS4 and showed band
around 700bp. No genetic variation was found among the isolates. A field trial
with 35 rice germplasm was conducted during the Transplanted Aman season
to screen the Rhizoctonia solani resistant germplasm in BRRI research field.
BR11 was used as susceptible variety. Highest relative lesion height (97%) was
recorded in susceptible check BR11. The lowest relative lesion height (15%)
was recorded in genotype Var24. It was revealed that three genotypes (Var23,
Var24 and Var29) were found resistant out of 35 genotypes tested. These
germplasm could be used in future rice breeding programmes aimed at
improving resistance to sheath blight.
Description:
A Thesis
Submitted to the Faculty of Agriculture
Sher-e-Bangla Agricultural University, Dhaka
in partial fulfilment of the requirements
for the degree of
MASTERS OF SCIENCE (MS)
IN
PLANT PATHOLOGY SEMESTER:
