Surface coating treatment of potato seed tuber is one of effective methods in controlling tuber-borne common
scab. Microbicide chemicals are generally used for the seed treatment, while the post-distillation slurry of barley-shochu can also have the similar effect to reduce the population density of plant pathogen infected seed tubers, resulting in the decrease of disease incidence in the daughter tubers as well as the microbicide fluazinam treatment (Tomihama et al., 2018). In this study, we compared the effect of seed treatment with post-distillation slurry and with microbicide on the community structures of bacteria associated with periderm of seed tubers, using amplicon sequencing analysis of 16S ribosomal RNA genes. The microbicide treatment drastically reduced the population of culturable bacteria and affected the community structures of phylogenetically broad bacteria. Especially, abundant ratio was decreased for Bacillus spp., which is one of the predominant in the seed tubers and the antagonist against plant pathogen. It is likely that the subset of thus influenced bacteria, in turn, migrated to the daughter tubers along the growth of potato plant, and subsequently affected the surface community of the daughter tubers. In contrast, the post-distillation slurry treatment promoted the increase in the ratio of Bacillus spp., while mostly maintained the original bacterial community of seed tubers. Therefore, it is estimated that the seed treatment with the post-distillation slurry is a sustainable approach in controlling the tuber-borne potato scab at lower risk without disturbing the bacterial ecosystem in the seed tubers.
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