Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/7/2013
Publication Date: 4/1/2013
Citation: Liu, Q., Chen, J., Munyaneza, J.E., Civerolo, E.L., Wallis, C.M. 2013. Scanning electron microscopy and in vitro cultivation of endophytic bacteria from potato tubers related to Zebra Chip disease. Canadian Journal of Plant Pathology. 35:192-199. Interpretive Summary: Zebra chip disease (ZCD) drastically reduces the value of potatoes in North America. Currently, no measure can effectively control ZCD. Previous studies on other potato diseases indicated that endophytic bacteria affected disease development. Yet, no information is available regarding endophytic bacteria related to ZCD. In this study, endophytic bacteria were observed in phloem tissues of ZCD potatoes by scanning electron microscope and isolated from ZCD-affected and non-ZCD affected potato tubers (cultivar ‘Atlantic’). Among the bacterial species isolated, seven were only isolated from ZCD-affected potato tubers and four species were only isolated from non-ZCD potato tubers. Further analysis showed that a bacterium, Microbacterium sp., was more associated with ZCD tubers than other bacteria. Results from this study are useful not only for understand the disease biology but also for future exploration of ZCD biocontrol because of the available bacterial cultures.
Technical Abstract: Zebra chip disease (ZCD) drastically reduces the quality and market value of potatoes in North America. The disease is associated with a phloem-limited alpha-proteobacterium, “Candidatus Liberibacter solanacearum”. No effective measure is currently available to control ZCD. It is known that endophytic bacteria colonize internal plant tissues and can affect the development of several potato diseases. However, there is no information about endophytic bacteria related to potato ZCD. In this study, endophytic bacteria in potato (cultivar ‘Atlantic’) were examined by scanning electron microscopy (SEM) and analyzed by in vitro cultivation method. SEM revealed bacterial cells of bacilli, coci, and pleomorphy in phloem tissues of ZCD tubers. In vitro cultivation retrieved a total of 85 bacterial strains, 51 from ZCD tubers and 34 from non-ZCD tubers. The bacterial strains were identified into 16 genera. Seven (Brachybacterium, Klebsiella, Microbacterium, Paenibacillus, Staphylococcus, Stenotrophomonas and Variovorax) were only isolated from ZCD-afffected potato tubers. Four (Bosea, Nocardia. Sphingomonas, and Sphingopyxis) were only isolated from non-ZCD potato tubers. PCR analyses using genus-specific primer sets, however, detected all bacteria in both ZCD or non-ZCD potato tubers, but the frequency varied. Microbacterium sp. appeared to be more associated with ZCD tubers than other studied bacteria.