Genetic diversity of Verticillium dahliae isolates from mint detected with genotyping by sequencing

Authors: DUNG, J - Oregon State University; Knaus, Brian; FELLOWS, H - Oregon State University; Grunwald, Niklaus - Nik; VINING, K - Oregon State University

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2019
Publication Date: 6/27/2019
Citation: Dung, J., Knaus, B.J., Fellows, H., Grunwald, N.J., Vining, K. 2019. Genetic diversity of Verticillium dahliae isolates from mint detected with genotyping by sequencing. Phytopathology. 109(11):1966-1974. https://doi.org/10.1094/PHYTO-12-18-0475-R.
DOI: https://doi.org/10.1094/PHYTO-12-18-0475-R

Interpretive Summary: Verticillium wilt is the most important disease threatening the commercial production of peppermint grown for essential oil. An important long-term goal for peppermint breeders is the production of cultivars with resistance to Verticillium wilt. Before that can be accomplished, a better understanding of the genetic variation contained in populations of the Verticillium wilt pathogen are needed. We characterized the extent of phenotypic and genetic diversity present in contemporary and archival populations of Verticillium dahliae from mint fields in Oregon and other production regions of the U.S. We report that the population in the Pacific Northwest can be described as one common genetic group and four relatively rare genetic groups. These results indicate low levels of genetic diversity. Knowledge of the genetic structure of V. dahliae in the Pacific Northwest will inform breeders about the diversity of pathogenicity factors that may need to be considered in their breeding programs.

Technical Abstract: Verticillium wilt is the most important disease threatening the commercial production of peppermint grown for essential oil. An important long-term goal for peppermint breeders is the production of cultivars with resistance to Verticillium wilt. Before that can be accomplished, a better understanding of the genetic variation contained in populations of V. dahliae is needed. We characterized the extent of phenotypic and genetic diversity present in contemporary and archival populations of Verticillium dahliae from mint fields in Oregon and other production regions of the U.S. using genotyping by sequencing, PCR assays for mating-type and pathogenic race, vegetative compatibility group (VCG) tests, and aggressiveness assays. We report that the population in the Pacific Northwest can be described as one common genetic group and four relatively rare genetic groups. Eighty-three percent of the isolates belonged to VCG2B, and all isolates possessed the MAT1-2 idiomorph and were characterized as pathogenic race 2. These results indicate low levels of genetic diversity and a negligible risk of sexual recombination in populations of this host-adapted pathogen population. Knowledge of the genetic structure of V. dahliae in the Pacific Northwest will inform breeders about the diversity of pathogenicity factors that may need to be considered in their breeding programs.