SURVEY ON NECK BLAST DISEASE OF RICE CAUSED BY Magnaporthe oryzae AND ITS In-vitro MANAGEMENT

Abstract

The survey on prevalence of rice neck blast was conducted and samples were collected from the farmers’ field of selected area of Bogura and Rangpur districts which were reported to have neck blast infestation by the regional agricultural extension centers during Boro season 2016-2017. During the survey, disease incidence and disease severity of rice neck blast in the eight surveyed villages were recorded and blast infected leaf and neck samples were collected for the invitro

study. The in-vitro study was carried out at the molecular laboratory of Plant Pathology Division of Bangladesh Rice Research Institute (BRRI), Gazipur-1701, during the period of January to June, 2017 to isolate the blast pathogen and to study its morphological and pathogenic characteristics. Among the surveyed villages, blast incidence was found significantly higher at Horishwor (94.34%) in Rangpur district and Nandiyarpara (96.5%) in Bogura district. Significantly higher blast severity were observed at Nandiyarpara (8.33) in Bogura and at Dhormodas Lokhonpara (7), Lalchadpur (6.33) and Horishwor (8.33) in Rangpur district. Disease incidence and disease severity was found higher for fields following annual two rice-crop sequence than the fields following annual one rice cultivation. From the morphological study of the derived eight isolates from the field samples, it was evident that the disease was caused by Magnaporthe oryzae, as the isolates produced hyaline, pyriform three celled conidia (16.7-26.05 x 5.57-8.58 μm 2 in size) and they were able to reestablish the disease in in-vitro pathogenicity test. The isolates were treated with

eight common fungicides used for blast treatment by poison bait technique and

the result showed significantly similar effect of

Royal 75 WDG, Sunzoxy 32.5 SC, Navera 28 SC, Nativo 75 WG, Agronil 560 SC and Sunchance 75WG on mycellial growth of Magnaporthe oryzae isolates while Deconil 50 SC and Archer 75 WP had 71.85% and 75.08% inhibition on mycelial growth of the isolates.