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Title: An ephemeral sexual population of Phytophthora infestans in the northeastern United States and Canada

Author
item DANIES, GIOVANNA - Cornell University
item MYERS, KEVIN - Cornell University
item MIDEROS, MARIA - Universidad De Los Andes
item RESTREPO, SILVIA - Universidad De Los Andes
item Martin, Frank
item COOKE, DAVID - The James Hutton Institute
item SMART, CHRISTINE - Cornell University
item RISTAINO, JEAN - North Carolina State University
item SEAMAN, ABBY - Cornell University
item GUGINO, BETH - Pennsylvania State University
item Grunwald, Niklaus - Nik
item FRY, WILLIAM - Cornell University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2014
Publication Date: 12/31/2014
Citation: Danies, G., Myers, K., Mideros, M.F., Restrepo, S., Martin, F.N., Cooke, D.E., Smart, C.D., Ristaino, J.B., Seaman, A.J., Gugino, B.K., Grunwald, N.J., Fry, W.E. 2014. An ephemeral sexual population of Phytophthora infestans in the northeastern United States and Canada. PLoS One. 9(12):e116354. doi: 10.1371/journal.pone.0116354.

Interpretive Summary: This manuscript examines a unique population of the pathogen that causes late blight of potato (Phytophthora infestans) that was identified in the NE of the USA in 2010/11. This pathogen usually reproduces asexually in the USA and Canada but the results of this submission indicate the unique population arose from sexual recombination.

Technical Abstract: Phytophthora infestans, the causal agent of late blight disease, has been reported in North America since the mid-nineteenth century. In the United States the lack of or very limited sexual reproduction has resulted in largely clonal populations of P. infestans. In 2010 and 2011, but not in 2012 or 2013, 20 rare and diverse genotypes of P. infestans were detected in a region that centered around central New York State. The ratio of A1 to A2 mating types among these genotypes was close to 1:1. These genotypes were diverse at the glucose-6-phosphate isomerase locus, differed in their microsatellite profiles, showed different banding patterns in a restriction fragment length polymorphism assay using a moderately repetitive and highly polymorphic probe (RG57), were polymorphic for four different nuclear genes and differed in their sensitivity to the systemic fungicide mefenoxam. This diversity is consistent with a recombinant population, and two tests (the index of association and the pairwise homoplasy index) failed to reject the hypothesis that these individuals were a recombinant population. These new genotypes were monomorphic in their mitochondrial haplotype that was the same as US-22. Through parentage exclusion testing using microsatellite data and sequences of four nuclear genes, recent dominant lineages US-8, US-11, US-23, and US-24 were excluded as possible parents for these genotypes. Further analyses indicated that US-22 could not be eliminated as a possible parent for 14 of the 20 genotypes. We conclude that US-22 could be a parent of some, but not all, of the new genotypes found in 2010 and 2011. There were at least two other parents for this population and the genotypic characteristics of the other parents were identified.