PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS AND MULTILOCUS SEQUENCE ANALYSIS OF BANANA SOFT ROT BACTERIA IN CHINA
Q. Liu, Y. Yuan, J. Liang, C. Wei, Q. Zhang, H. Li
Bacterial soft rot is a new disease that, in recent years, has caused significant economic losses to banana production in China. Four bacterial isolates representative of a larger group of bacteria recovered from diseased banana plants located in different regions of China and a strain of Dickeya zeae (Ec1) from rice, used as control, were characterized by morphological, physiological, biochemical, and molecular assays. Results showed that the bacterial isolates from banana were Gram-negative, rod-shaped with multiple flagella, and produced a brown pigment on NGM medium (nutrient agar supplemented with 1% glycerol), indicating that they belong to Dickeya. Physiological and biochemical assays revealed that all bacteria from banana were in fact isolates of D. zeae differing from Dickeya dieffenbachiae and Dickeya paradisiaca. Phylogenetic analysis in comparison with sequences of 14 strains of Dickeya spp. retrieved from GenBank was done using the concatenated partial sequences of the seven housekeeping genes dnaA, dnaJ, dnaX, gyrB, recN, gapA, and mdh. All banana isolates were closely related to D. zeae and distinct from other Dickeya spp. The germination rate of rice seeds soaked with bacterial culture supernatant (crude toxin) and toxin bacteriostatic test results showed that the banana strains were different from D. zeae Ec1 in toxin production.