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Title:   Author  item
                                            DUNN, A - Cornell Universityitem
                                            BRUENING, S - Cornell Universityitem
                                            Grunwald, Niklaus

                                                         - *Nik*item
                                            SMART, C - Cornell University
  Submitted to: Phytopathology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 4/3/2014
                                    Publication  Date: 10/15/2014
                                    Citation: Dunn, A.R., Bruening, S.R., Grunwald, N.J., Smart, C.D. 2014. Evolution of an experimental population of Phytophthora capsici in the field. Phytopathology. 104(10):1107-1117.Interpretive Summary: The plant pathogen Phytophthora capsici causes disease on a range of cucurbits and this disease is important to US agriculture. Populations of the vegetable pathogen Phytophthora capsici are genetically diverse and sexually reproducing. We established an experimental population with two parental strains of opposite sex. This population was sampled and characterized genetically over several years. As expected the population reproduced sexually and showed a population structure similar to that sampled in a commercial field nearby. These results suggest that several genetic mechanisms are at play including recombination, mutation and loss of heterozygosity that play a role in maintaining the high levels of diversity observed in P. capsici populations. This work provides novel insights into the evolution of plant pathogens.
                                Technical Abstract: Populations of the vegetable pathogen Phytophthora capsici are often highly diverse, with limited gene flow between fields. To investigate the structure of a newly established, experimental population, an uninfested research field was inoculated with two single zoospore isolates of P. capsici in September 2008. From 2009 through 2012, approximately 50 isolates of P. capsici were collected from the field each year and genotyped using five microsatellite loci. The same two isolates were also crossed in the lab. High levels of diversity were detected in the research field, with 26 to 37 unique multilocus genotypes detected each year. Through 2012, genotypic diversity did not decline, and no evidence of genetic drift was observed. However, during the 2011 and 2012 growing seasons, a total of four new alleles not present in either parental isolate were observed in the field. Selfing (but not apomixis) was observed at low frequency among in vitro progeny. In addition, evidence for loss of heterozygosity was observed in half of the in vitro progeny. These results suggest that recombination, mutation and loss of heterozygosity can play a role in maintaining the high levels of diversity observed in P. capsici populations.


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