EVALUATION OF RICE CULTIVARS AGAINST RICE BLAST AND IN VITRO MANAGEMENT OF MAGNAPORTHE ORYZAE

Abstract

A set of investigation comprising four experiments was conducted in the Department of Plant Pathology, Sher-e-Bangla Agricultural University, during three consecutive year 2016, 2017, 2018 from March to June in Bangladesh. The investigation was aimed to find out the pathogenic variability of rice blast pathogen Magnaporthe oryzae, its epidemic nature in rice growing areas in Bangladesh and finally its in vitro management including varietal screening against the disease. For the epidemic nature of rice blast and its pathogenic variability, a survey was conducted in different rice growing regions in Bangladesh from where the disease incidence and disease severity data and subsequently the blast infected leaves and stems samples were collected. Survey data revealed that the highest disease incidence (60%) was found in Bogura district, whereas the lowest (10%) was observed in Dhaka, Sunamgonj, and Moulvi Bazar districts. The highest (5%) disease severity was recorded in the Kishoregonj District, while the lowest (3.33%) was in the Dinajpur District. Twenty-six (26) isolates of Magnaporthe oryzae were isolated and identified from the sample collected from survey areas. The highest mycelial radial growth of M. oryzae (29.67 mm) was recorded for OMA, whereas the lowest (15.00 mm) in PR S DA culture media. In 7 days after culture, the highest redial mycelial (51.50 mm) was recorded from the isolate of PBSL20, while the shortest (32.00 mm) was from the isolate of MNKL12. At 14 days after incubation, the longest redial mycelial growth (85.83 mm) was found from the isolates of DKRP19, while the shortest redial mycelial growth (60.33 mm) was found from the isolates of MBBL09. In case of in vitro management among the 12 fungicides, maximum growth inhibition (100%) of M. oryzae was found in Folicular 250 EC (Tebuconazole-10%), Seltima 100 CS (Pyraclostrobin-10%), Filia 525 SE (Propiconazole-12.5%) + Tricyclazole-40%)) and Difar 300 EC ((Difenoconazole15%)

+ Propiconazole-15%)), whereas the lowest (0.00%) inhibition was recoded in Autostin 50 WDG. Among 8 botanicals Neem, Alamanda, and Aloe vera were performed best and significantly inhibited radial mycelial growth. In vitro radial mycelial growth of M. oryzae with bio-agent (Trichoderma harzianum) in PDA media trial the radial mycelial growth of M. oryzae was 0.00 mm irrespective of inoculation design. In contrast, the radial mycelial growth of bio-agent Trichoderma harzianum was 41.67 mm, 36.67, and 41.67 mm. In control condition, radial mycelial growth of test fungus and bio-agent was 12.33 mm and 41.67 mm, respectively. Among 17 rice germplasms tested, only two cultivars, Jeera Vog and BRRI dhan33, were found resistant against M. oryzae in the uniform rice blast nursery.

Key words: Rice blast, Magnaporthe oryzae, in vitro, fungicide, botanical, bio-agent