Biocontrol of Fusarium fujikuroi, a causal agent of bakanae disease of rice by antagonistic endophytic bacteria
摘要
Fusarium fujikuroi causes bakanae disease, which poses a great threat to rice production in Bangladesh. The aim of the study was to isolate and screen rice endophytic bacteria against F. fujikuroi to control the bakanae disease of rice. A total of 25 endophytic bacteria were isolated from rice plants from farmers’ fields in the Gazipur district of Bangladesh of which five isolates 5ST, 5RT, 1 L, 9 L and 10 L showed in vitro antagonistic activity against F. fujikuroi FF1 (Accession No. PP060638). The isolate 9 L inhibited the mycelial growth maximum of 80.59%. Volatile substances of the antagonistic bacterial isolates inhibited the mycelial growth of F. fujikuroi FF1 ranging from 72 to 100%. The culture filtrate of the isolates performed 100% mycelial growth inhibition of the test pathogen. Production of hydrolytic enzymes and volatile compounds was investigated for the antagonistic isolates. All five isolates 5ST, 5RT, 1 L, 9 L and 10 L, were positive for amylase, protease and cellulase production but negative for lipase. In the case of antifungal volatile compounds, all the bacterial isolates produced ammonia, isolates 5ST, 5RT, and 9 L produced HCN and isolate 9 L was also positive for acetoin. All five isolates significantly reduced the bakanae disease incidence and disease severity index under pot culture conditions. The isolates were characterized and identified by physiological, biochemical, and molecular tests. Among the 5 isolates, 5ST and 5RT were identified as Alcaligenes faecalis, and 1 L, 9 L and 10 L were identified as Burkholderia seminalis, Pseudomonas citronellolis and Enterobacter mori, respectively. Further trial is needed to evaluate efficacy of the isolates under field conditions as a biocontrol agent for sustainable rice production.