Poster # 22

Unraveling two major evolutionary lineages in Phakopsora pachyrhizi, the causal agent of Asian soybean rust
V. D. ROCHA, E. G. C. FERREIRA, F. M. CASTANHO, M. K. KUWAHARA, C. GODOY, M. MEYER, K. PEDLEY, R. T. VOEGELE, I. V. GRIGORIEV, K. BARRY, M. LOEHRER, U. SCHAFFRATH, C. SIRVEN, S. DUPLESSIS, F. C. M. GUIMARÃES
Empresa Brasileira de Pesquisa e Agropecuária (Embrapa Soja), Laboratório de Biotecnologia Vegetal, Londrina (Paraná), Brazil

Phakopsora pachyrhizi is a biotrophic basidiomycete fungus responsible for Asian soybean rust (ASR) disease, that represents a serious threat to soybean production, especially in South America. We elucidated the evolutionary relationships and population structure of P. pachyrhizi by analyzing whole-genome re-sequencing data from 45 P. pachyrhizi isolates collected across the world in diverse regions. Our phylogenetic analysis revealed that P. pachyrhizi isolates formed two distinct lineages (Pp1 and Pp2). The lineage Pp1 comprised highly-divergent isolates confined to three specific regions (Asia, Australia, and Hawaii). Meanwhile, members of the lineage Pp2 likely dispersed from their ancestral area (Asia) towards other continents, including Africa and America. Consistent with the phylogenetic results, both principal component analysis (PCA) and Bayesian clustering (fastSTRUCTURE) supported that each lineage constituted a separate genetic cluster. Notably, we detected moderate levels of genetic admixture between the two described lineages. This finding suggests the occurrence of gene flow between those lineages likely through mechanisms such as parasexual recombination or cryptic sexual reproduction, considering that the sexual stage of P. pachyrhizi is still unknown. Despite the high genetic differentiation (FST= 0.46) between Pp1 and Pp2, clonal spore propagation may explain the lowest mean of nucleotide diversity (π= 1.18x10-4) observed in Pp2.