Rice bacterial foot rot disease caused by Dickeya zeae in Taiwan.
Rice bacterial foot rot is a new bacterial disease of rice found in Taiwan recently. Symptoms of the disease include brown sheath rot and dark brown decay of the tillers. The diseased samples were collected in Chiayi County and bacteria were isolated from the symptomatic tissues. Pathogenicity of the bacteria was verified by Koch's postulates. The pathogen was further determined as Dickeya zeae by Biolog identification and multi-gene (16S rDNA, gyrB, and dnaX) sequence analysis. The pathogen could also infect several important crops such as maize, potato, carrots and Chinese cabbage. It could grow at wide range of temperatures, 10-40°C, with optimal range in 30-35°C. The selected 26 rice varieties were all infected by the pathogen. Among these tested varieties, japonica rice variety, 'TK8' was most susceptible to the pathogen, with an average incidence of 94.44%. An In vitro agrochemical screening test showed that 20% oxolinic was the most effective inhibitor on bacterial growth. A greenhouse trial showed that the chemical could only protect the rice plants if applied before the pathogen infection. The results suggested that 20% oxolinic could be recommended as an effective chemical to control the rice bacterial foot rot disease in the field.