AUTHOR=Mihalyov Paul D. , Garfinkel Andrea R. 

TITLE=Discovery and Genetic Mapping of PM1, a Powdery Mildew Resistance Gene in Cannabis sativa L.

JOURNAL=Frontiers in Agronomy

VOLUME=3

YEAR=2021

URL=https://www.frontiersin.org/journals/agronomy/articles/10.3389/fagro.2021.720215

DOI=10.3389/fagro.2021.720215

ISSN=2673-3218

ABSTRACT=<p>Powdery mildew is among the most common diseases of both hemp- and marijuana-type cultivated <italic>Cannabis sativa</italic>. Despite its prevalence, no documented studies have characterized sources of natural genetic resistance in this pathosystem. Here we provide evidence for the first resistance (<italic>R</italic>) gene in <italic>C. sativa</italic>, represented by a single dominant locus that confers complete resistance to an isolate of the powdery mildew pathogen <italic>Golovinomyces ambrosiae</italic>, found in the Pacific Northwest of the United States. Linkage mapping with nearly 10,000 single nucleotide polymorphism (SNP) markers revealed that this <italic>R</italic> gene (designated <italic>PM1</italic>) is located on the distal end of the long arm of one of the largest chromosomes in the <italic>C. sativa</italic> genome. According to reference whole genome sequences and Sanger sequencing, the marker was tentatively placed in a cluster of <italic>R</italic> genes of the nucleotide-binding site (NBS) and leucine-rich repeat (LRR) protein type. <italic>PM1</italic>'s dominant behavior, qualitative penetrance, and a co-segregating qPCR marker to track its inheritance were confirmed in two separate genetic backgrounds totaling 185 recombinant F1 plants. The goal of this study is to provide a foundation for the discovery and characterization of additional sources of genetic resistance to pathogens that infect <italic>C. sativa</italic>.</p>