Potato

A walk on the wild side: exploring the functional potential of Andean soil microbiomes to enhance tolerance of potato to late blight disease  

Potato is the 4th most important food crop worldwide. Taxonomically, potatoes consist of all the tuber-producing species from the genus Solanum section Petota, and it is divided into wild species (Solanum spp.), cultivated landraces (S. tuberosum group Andigena, Phureja, Stenotomum, and Chilotanum), and modern cultivars (S. tuberosum group Tuberosum). The center of origin and diversity of potatoes is the Andean region in South America, where it was domesticated almost seven thousand years ago. Later, during the Spanish Conquest, it was introduced to Europe, where modern cultivars appeared as the result of multiple breeding events between potatoes from the group Andigena and Chilotanum. Moreover, propagation from true potato seeds and hybrid potato breeding have been developed in recent years, which takes advantage of heterosis (i.e., hybrids display enhanced performance relative to their parental lines). The long domestication history and the broad cultivation range of potatoes make this group of species a great candidate to study the relationship between plant domestication and microbiome assembly. In this study, we will examine how habitat domestication and breeding affect the assembly of the root microbiome in potato and its effect on tolerance to late blight caused by Phytophthora infestans.

Results

We collected soil from 14 sites along the Ecuadorian Highlands (center of origin), and for each site, we took the two types of soil (native and agricultural). The soils were transported to Quito, where potato in vitro plants from the Superchola variety were transferred to pots with 1:1 soil:perlite mix. After 12 weeks, half of the plants were inoculated with Phytophthora infestans. Severity was assessed after 7 days. We found that native soil induced a significant reduction in severity compared to agricultural soil. From this experiment, bulk soil, rhizosphere, and root were sampled for 16s amplicon sequencing. For the three compartments analyzed, significant differences were found between soil types (native vs. agricultural) for all sites. Differential abundance (DA) analyses were performed to identify specific ASV enriched and depleted in native compared to agricultural soils in each site. A signature in the taxonomy of the ASV present in each soil was identified, with an overrepresentation of diderm bacteria (Proteobacteria, Planctomycetota, and Acidobacteriota) in the native soils and monoderm bacteria (Firmicutes and Actinobacteriota) in the agricultural soils. For future experiments, we identify 17 bacterial isolates from native soils as candidates for validation in bioassays for tolerance induction to P. infestans in potato.