Abstract Detail

Population Genetics/Genomics

Oliveira, Luiz [1], Rody, Hugo [2], Borges, Leandro [2], Grijalba, Pablo [3], Almeida, Alvaro [4], Ferreira, Thiago [2].

Disentangling the genealogical relationships among cryptic species of pathogenic Cercospora of soybean through genotyping-by-sequencing.

The advent of innovative, powerful molecular tools has the potential to shed further light on the intricacy of species diversity within plant pathogens, including cryptic speciation. Historically, a single species (Cercospora kikuchii) was known to cause Cercospora leaf blight (CLB) and purple seed stain (PSS) in soybean. More recently, two other species (C. sigesbeckiae and C. flagellaris) have also been associated with CLB and PSS. Analysis of Genotyping-by-Sequencing (GBS) data may assist in disentangling the relationships among those three species and probing whether additional species may also be associated with CLB and PSS in soybean. For GBS analyses, DNA libraries of monoconidial cultures of Cercospora from the top three soybean producing countries (Argentina, Brazil, and USA) and cultures of five closely-related species were subjected to sequencing using the Illumina HiSeq 2500 plataform. The raw reads underwent demultiplexing, filtering, trimming, and de novo assembling. Molecular analyses of Dataset 1 (60 isolates, 550 loci, 43.988 bp) and Dataset 2 (31 isolates, 826 loci, 66.079 bp) revealed surprising details about the evolutionary history of Cercospora associated with CLB and PSS. Phylogenetic analyses and Principal Component Analyses organized the isolates into seven distinct groups (genealogical lineages), three of which (lineages 5-7) were new. At the molecular level, C. kikuchii was undistinguishable from C. sigesbeckiae given that the two species shared a common gene pool; probably those species correspond to a single taxonomic entity within Lineage 1. Lineage 1 was present in Argentina, Brazil, and USA. Five Lineages (2, 3, 5, 6, and 7) likely corresponded each to an undescribed species of Cercospora; they were from Argentina and Brazil. Lineage 4, a lineage that contained C. flagellaris, was closely related to Lineage 5; both lineages were from the EUA. The low levels of genetic diversity of Lineage 1 contrasted sharply with the high levels of Lineages 2 and 3. Those findings confirmed that cryptic species are associated to CLB and PSS and urges new strategies for disease management and phytosanitary vigilance at a global scale.

1 - Av. P. H. Rolfs - Dept Bioquimica S/n, Caixa Postal, 247 Campus UFV, Vicosa (MG), MG, 36570-000, Brazil
2 - Universidade Federal de Viçosa, Av. P. H. Rolfs - Dept Bioquimica s/n, Viçosa, MG, 36570-000, Brazil
3 - University of Buenos Aires, Department of Plant Production, Buenos Aires, Argentina
4 - Embrapa, Londrina, PR, Brazil

Keywords:
genetic diversity
species complex
pathogen.

Presentation Type: Poster
Session: P, Population Genetics/Genomics Posters
Location: Arizona Ballroom/Starr Pass
Date: Monday, July 29th, 2019
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPG003
Abstract ID:326
Candidate for Awards:None