Erwinia carotovora subsp. wasabiae subsp. nov. Isolated from Diseased Rhizomes and Fibrous Roots of Japanese Horseradish (Eutrema wasabi Maxim.)

Abstract

A gram-negative bacterium with peritrichous flagella isolated from internally discolored rhizomes of Japanese horseradish, Eutrema wasabi Maxim. (Japanese common name, wasabi), was compared with other soft rot Erwinia spp. The wasabi bacterium induced soft rot on slices of various vegetables, such as wasabi rhizomes, potato tubers, and carrot and radish roots, on midribs of chinese cabbage and intact wasabi, and on tomato and tobacco plants, but not on rice, corn, or chrysanthemum. Although this bacterium was more similar to Erwinia carotovora than to Erwinia chrysanthemi in physiological and biochemical properties, it differed from E. carotovora subsp. carotovora, E. carotovora subsp. atroseptica, and E. carotovora subsp. betavasculorum in being negative in the o-nitrophenyl-β-d-galactopyranoside test, curd formation and peptonization of litmus milk, growth in yeast extract-peptone broth containing 0.075% KCN or 5% NaCI, growth at 36°C, and fermentation of lactose, raffinose, and melibiose. This bacterium also differed in having a 24-h lag in galactose fermentation, rapid fermentation of trehalose, and different serological properties. The guanine-plus-cytosine content of deoxyribonucleic acid was 51.4 to 51.7 mol%. Such significant differences warranted the designation of the wasabi bacterium as a new subspecies of E. carotovora, and the name Erwinia carotovora subsp. wasabiae subsp. nov. is proposed. Strain SR91 (=ATCC 43316, and PDDCC 9121) is designated the type strain.