The Potential use of Bacterial Diversity Analysis of Soft Rotted Potato Tubers and Their Geocaulospheres

The soft rot caused by Pectobacterium and Dickeya spp. is among the most important potato disease, responsible for outbreaks worldwide. In 2018, potato tubers (cultivar Lady Claire) with and without visible soft rot symptom, together with their geocaulospheres were sampled from the field in Bačka region (Serbia). The 16S rRNA Next Generation Sequencing (NGS) of tubers with and without soft rot symptom and their corresponding soils was performed to detect differences in microbial diversity and, using this data to predict causal agent(s) of disease and which samples are potentially best for isolating biocontrol strains. The ubiquitous soil bacteria from the phyla Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes were dominant in all samples. The sequences identified as Pectobacterium aroidearum, P. carotovorum, and P. polaris were present in all tested samples and it can be hypothesized that they caused soft rot. The K3 sample showed the presence of genera with potential antimicrobial activity (Pseudomonas, Arthrobacter, Chryseobacterium, Bacillus, and Exiguobacterium). This result shows that diversity analysis could be used for checking for the presence of potential antagonistic bacteria at infected sites. Also, following the presence or absence of particular taxa could point out a capacity of soil to endure a growth season without an outbreak of soft or to maintain it without significant losses. This is a new approach to interpreting the results of the diversity of bacterial communities of tubers and can be useful for screening the health status of the soil.