Identification and Characterization of a New Enterobacter Onion Bulb Decay Caused by Lelliottia amnigena in China

Abstract

Objectives: Enterobacter is a genus with numerous species associated with clinical relevance, plants, foods and environmental sources. However, the taxonomy of Enterobacter is complicated and confusing. In order to identify the taxonomy of the causal agent isolated from decay onion bulbs in China and provide an example to identify plant pathogens, we used biochemical technologies in combination with molecular biology to confirm the status of the pathogen. Methods: In this study, biochemical test, colonial and microscopic morphology analysis, 16S rRNA gene sequencing and multilocus sequences analysis (MLSA) based on partial sequencing of rpoB, atpD, gyrB and infB were performed on the isolates obtained from the decayed onion bulbs. According to the biochemical characteristics and genetic relationship, we compared the pathogen with related strains obtained from BLASTn alignment. Finally, pathogenicity test was performed on healthy onion bulbs to verify the Koch’s postulates. Results: Biochemical test, colonial and electron microscopic morphology indicated that the pathogen is gramnegative, belongs to the genus Lelliottia and in combination with phylogenetic analysis, it is most similar to L. amnigena. Conclusion: To our knowledge, this is the first report of L. amnigena naturally causing soft rot disease on harvested onion.