Evaluation of Disease Severity and Molecular Relationships Between Isolates on Species in New Hampshire.

Quinoa is a potential new crop for New England; however, its susceptibility to downy mildew, caused by , is a key obstacle for cultivation. The objectives of this study were to evaluate differential resistance within the genus, identify novel sources of resistance for use in future genetic studies or breeding programs, and investigate phylogenetic relationships of isolates from different hosts. The long-term goal of this research is to develop a resistant variety of quinoa to be grown in New England. Field trials conducted at the University of New Hampshire evaluated downy mildew disease severity on 10 accessions representing four species. Disease severity for each treatment was compared and significant differences in disease severity were observed between accessions. var. ecotypes collected from Rye Beach, New Hampshire and Appledore Island, Maine exhibited the lowest disease severity over the growing season. was isolated from each accession, and sequences were compared. Phylogenetic analyses suggest no effect of host species on sequence similarity; however, isolates are shown to cluster by geographic location. This research provides the first step in identifying potential New England native sources of resistance to downy mildew within the genus and provides preliminary information needed to further investigate resistance at the genomic level in spp.