Molecular detection of Peronospora variabilis in quinoa seeds and phylogeny of the quinoa downy mildew pathogen in South America and the United States

As Quinoa production increases in response to growing global demand for the crop, it is necessary to develop improved production practices that will support sustainable production. To that end, this paper examines the ability of the Bacillus species of bacteria to colonize quinoa and to promote quinoa growth, and seeks to identify source of inoculum for Peronospora variabilis, the cause of the quinoa downy mildow disease. Bacillus populations isolated from Pennsylvanian Chenopodium album, Ecuadorean C. quinoa, and Bolivian C. quinoa were screened for the ability to solubilize tricalcium phosphate and this phenotype was paired with 16S sequence data to determine if there were species based patterns of tricalcium phosphate solubilization. Seed-based detection methods using sequencing and PCR with specific primers were developed to detect seedborne oospores of P. variabilis. It was found that seedborne oospores likely play a significant role in the spread of quinoa downy mildew, making the development of management methods for these seedborne oospores critical. Combining these research themes, the potential for Bacillus to reduce the severity of quinoa downy mildew was tested.