Epsilon Archive for Student Projects

Abstract

Rice blast caused by Magnaporthe grisea is one of the major and recurrent threats for sustainable rice production in Bangladesh. To mitigate this problem, the current study was aimed to investigate the efficacy of silver nanoparticles against rice blast disease and farmers’ perception or knowledge about rice blast disease management in Bangladesh. There have been relatively few studies on the applicability of nanoparticles to control blast diseases in Bangladesh. This study was done into two parts: firstly, face to face interviews to understand the farmers’ perception as well as to find out their needs and secondly laboratory experimentation to find out the efficacy of silver nanoparticles against M. grisea as well as rice blast disease management under controlled conditions. Close-ended questions were prepared for the interview and thirty farmers were interviewed. Farmers’ interviews indicated that 73% of the respondent farmers had experienced blast disease in their fields but only 30% of the respondent farmers were aware of rice blast disease and its management. Among the respondents, 89% of the farmers used chemicals in controlling rice blast disease but only 9% of the farmers had an opinion that spraying chemicals worked very well and 21% thought this method worked satisfactorily. Around 59% of respondents maintained close contact with extension workers and adopted new technologies according to their suggestions. In vitro assays indicated that silver nanoparticles had a significant inhibitory effect on the mycelial growth of rice blast pathogen. Effective concentration of the silver nanoparticles inhibiting mycelial growth by 50% (EC50) up to 9 days after incubation was 308.1 ppm. However, the inhibitory effect on mycelial growth significantly diminished at 12 days of incubation. To measure leaf blast disease severity, three concentrations (200, 400 and 800 ppm) of silver nanoparticles and a popularly used blast control fungicide Trooper 75WP were sprayed on rice seedlings that were 20-25 days old, 3 days before inoculation for preventive and 3 days after inoculation with spore suspension (105 conidia/ml+0.01% Tween 20) for curative measure. Only 1.77% and 3.23% leaf blast disease severity were found in preventive measure at 800 ppm concentration for Trooper 75 WP (standard dose of fungicide) and silver nanoparticles, respectively. Whereas untreated control plot exhibited more than 70.0% disease severity. In greenhouse assay, silver nanoparticles were highly effective in preventative application rather than curative application.