Abstract Detail

Host/Plant Pathogen Interactions and Plant Health Management

Salgado-Salazar, Catalina [1], Rivera, Yazmín [1], Crouch, Jo Anne [1].

Emergence of the impatiens downy mildew pathogen in the U.S. corresponded with a shift in population structure.

Plasmopara obducens is the newly emergent oomycete responsible for impatiens downy mildew disease (IDM). Since outbreaks began in 2004, IDM has almost eliminated U.S. impatiens production. In this study, we evaluated if there was a change in P. obducens population structure associated with the epidemic. We generated a 199-Mb genome assembly for P. obducens (94% of the non-repetitive genome), and identified 4,531 microsatellite motifs. We genotyped 468 pre- and post-epidemic P. obducens samples using 37 microsatellite markers. Population structure analysis identified six populations (P1-P6). Populations P1-P4 shared an identical rDNA profile, but populations P5 and P6 were divided between four rDNA groups. Prior to IDM epidemics, P1 and P2 dominated, existing as pure P1 or P2 genotypes (~65%), or moderately admixed P1/P2. The first epidemic IDM specimen collected in 2004 from TN showed an admixed microsatellite genotype: P1/P2/P5 (30:50:20). All post-epidemic samples clustered in populations P3-P6, with 50% showing admixed genotypes. In post-epidemic P3-P6 populations, admixture with P1 and P2 allelic profiles was uncommon. These data show that the recent emergence of IDM in the U.S. corresponded with a major shift in P. obducens populations, with endemic P1/P2 genotypes supplanted by novel genotypes. The presence of admixed individuals indicates gene flow between P. obducens populations, which may present difficulties for durable disease control implementation.

Related Links:
Crouch Lab

1 - USDA-ARS, Systematic Mycology & Microbiology, 10300 Baltimore Avenue, Building 010A, Beltsville, MD, 20705, USA

Keywords:
downy mildew
emergent diseases
population genetics
herbarium
oomycete
genome sequencing.

Presentation Type: Oral Paper:Papers for Topics
Session: 55
Location: Salon 2/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 4:15 PM
Number: 55005
Abstract ID:1317
Candidate for Awards:None