Abstract
Aggregate sheath spot disease of rice caused by Rhizoctonia oryzaesativae has emerged in higher incidence in North-Western region of Bangladesh. Thirty isolates of R. oryzae-sativae were studied by using morphological and molecular marker. Isolates were confirmed using specific primer where a single band of 1200bp was amplified. Two distinct groups relatively slow and faster were found in mycelal growth. Molecular characterization was done using four primers and DNA band ranged from 0.25 to 2.21 kb. A combined dendrogram was constructed which separated the isolates into three groups at 69.6% similarity level. All isolates placed in two major clusters except isolate RA-1 placed in cluster group III but were not grouped according to their geographic origins. Fast growing isolates have been placed in Group II while slow growing isolates in cluster group I. The similarity coefficient values of the dendrogram profile ranged from 0.36 to 0.98 with an average of 0.67. Diversity of different isolate showed that significant variation was present among the isolate and were not genetically identical.
 SAARC J. Agri., 16(2): 119-128 (2018)
Highlights
Sheath diseases of rice are the major constraints of rice production in Bangladesh
Somatic incompatibility has been used as a marker to identify isolates of Rhizoctonia oryzae-sativae in order to determine the survival of overwintering inoculum and dissemination of the fungus in rice field in Japan (Guo et al, 2006)
All isolates identified as R. oryzae-sativae by the presence of constricted hyphae and binucleate cells (Table 1) and using specific primers
Summary
Sheath diseases of rice are the major constraints of rice production in Bangladesh. Among them Rhizoctonia sheath diseases of rice are predominant comprise of sheath blight, sheath spot and aggregate sheath spot. Aggregate sheath spot of rice caused by Rhizoctonia oryzae-sativae, occurs in Bangladesh and in other countries including United states (Gunnel et al, 1984), Japan, Vietnam, India, Thailand, Iran, Venezuela, Uruguay and Australia (Cedeno et al, 1998, Rahimian et al.,1989, Gunnel et al, 1992, Lanoiselet et al, 2007). Knowledge of the population of pathogenic Rhizoctonia oryzae-sativae is essential for integrated control strategies; along with the understanding of the influence of other characteristics, including virulence, host range and adaptability to environmental conditions. Perhaps this is the first comprehensive report in which thirty isolates of R. oryzae-sativae collected from rice fields in Bangladesh.
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