Location: Sugarbeet and Potato ResearchTitle: Genetic diversity and structure in regional Cercospora beticola populations from Beta vulgaris ssp. vulgaris suggest two clusters of separate origin
|KNIGHT, NOEL - Cornell University|
|VAGHEFI, NILOOFAR - Cornell University|
|KIKKERT, JULIE - Cornell University|
|SECOR, GARY - North Dakota State University|
|RIVERA, VIVIANA - North Dakota State University|
|NELSON, SCOT - University Of Hawaii|
|PETHYBRIDGE, SARAH - Cornell University|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2019
Publication Date: 5/29/2019
Citation: Knight, N.L., Vaghefi, N., Kikkert, J.R., Bolton, M.D., Secor, G.A., Rivera, V.V., Hanson, L.E., Nelson, S.C., Pethybridge, S.J. 2019. Genetic diversity and structure in regional Cercospora beticola populations from Beta vulgaris ssp. vulgaris suggest two clusters of separate origin. Phytopathology. 109:1280-1292. https://doi.org/10.1094/PHYTO-07-18-0264-R.
Interpretive Summary: The sugarbeet disease Cercospora leaf spot is caused by the fungus Cercospora beticola. The fungus is known to be genetically diverse such that strains harvested from any given field are not likely to be related to each other. However, there has been little research to study how populations from other countries might be related to each other. This information is important because it might identify locations where aggressive or fungicide-resistant strains originate. For example, strains originating from seed production areas may suggest that the fungus can travel globally with seed used for planting. In this study, Cercospora populations were studied from eight geographical regions including two locations in New York, Canada, Chile, Eurasia, Hawaii, Michigan, and North Dakota. The results suggest that most populations originated from Europe. These findings may have implications for the seed industry and may suggest that further scrutiny is warranted by seed companies to ensure that Cercospora is not spread in contaminated seed.
Technical Abstract: Cercospora leaf spot, caused by Cercospora beticola, is a highly destructive disease of Beta vulgaris ssp. vulgaris worldwide. Cercospora beticola populations are usually characterized by high genetic diversity, but little is known of the relationships between populations from different production regions around the world. This information would be informative of potential pathways for pathogen movement and population origin. For the current study, the genetic diversity, differentiation, and relationships among C. beticola populations containing 948 isolates, across eight geographic regions, were quantified using 12 microsatellite markers. Genotypic diversity (Simpson’s complement index), ranged from 0.18 to one, while pairwise index of differentiation values ranged from 0.02 to 0.42, with the greatest differentiation detected between two New York populations. In these populations, evidence for recent expansion was detected. Assessment of population structure identified two major clusters, the first associated with New York, and the second with Canada, Chile, Eurasia, Hawaii, Michigan, New York – Farm 2 – 2015, and North Dakota. Gene flow between these regions indicated one source likely originating from Europe, and another of unknown origin. These results suggest a shared origin of C. beticola populations across regions, except for part of New York, where population divergence has occurred. These findings support a hypothesis of long-range pathways acting as a mechanism for dispersal of C. beticola.