Endemic and panglobal genetic groups and divergence of host-associated forms in world-wide collections of the wheat leaf rust fungus Puccinia triticina as determined by genotype by sequencing

Authors: Kolmer, James; HERMAN, ADAM - University Of Minnesota; ORDONEZ, MARIA - Pontifical Catholic University Of Ecuador; GERMAN, SILVIA - Instituto Nacional De Investigacion Argropecuaria, Urugary; MORGOUNOV, ALEXY - International Maize & Wheat Improvement Center (CIMMYT); PRETORIUS, ZACHARIAS - University Of The Free State; VISSER, BOTMA - University Of The Free State; ANIKSTER, YEHOSHUA - Tel Aviv University; ACEVEDO, MARICELIS - Cornell University

Submitted to: Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2019
Publication Date: 12/20/2019
Citation: Kolmer, J.A., Herman, A.C., Ordonez, M.E., German, S.E., Morgnounov, A., Pretorius, Z.A., Botma, V., Anikster, Y., Acevedo, M.A. 2019. Endemic and panglobal genetic groups and divergence of host-associated forms in world-wide collections of the wheat leaf rust fungus Puccinia triticina as determined by genotype by sequencing. Heredity. 124:397–409. https://doi.org/10.1038/s41437-019-0288-x.
DOI: https://doi.org/10.1038/s41437-019-0288-x

Interpretive Summary: Wheat is attacked by the rust fungus called Puccinia triticina, which causes the disease wheat leaf rust. There are many different forms or races of the wheat leaf rust fungus that vary in their ability to attack different resistance genes in wheat. This study characterized populations of the wheat leaf rust fungus from 11 different regions world-wide for molecular DNA variation, using the genotype by sequence approach. Populations that were more close geographically were also more similar for DNA markers. Subgroups of populations from different regions were highly similar to other subgroups from other continental regions which indicated migration of Puccinia triticina genotypes across regions. Collections from durum wheat were very distinct for DNA markers compared to collections from common or bread wheat. Collections of the rust fungus found only in Ethiopia on durum wheat are most likely the oldest type of leaf rust that is found on wheat, followed by other types found on durum wheat world-wide, and then collections from common wheat world-wide. This study provided further insight on the population genetics and migration of wheat leaf rust on a world-wide basis, which will be useful for designing strategies for reducing yield losses in wheat due to leaf rust infections.

Technical Abstract: The wheat leaf rust fungus, Puccinia triticina, is found in the major wheat growing regions of the world and is a leading cause of yield loss in wheat. Populations of P. triticina are highly variable for virulence to resistance genes in wheat and adapt quickly to resistance genes in wheat cultivars. The objectives of this study were to determine the genetic relatedness of worldwide collections of P. triticina using restriction associated genotype by sequencing. A total of 558 isolates of P. triticina from wheat producing regions in North America, South America, Europe, the Middle East, Ethiopia, Russia, Pakistan, Central Asia, China, New Zealand and South Africa were characterized at 6745 single nucleotide loci. Isolates were also tested for virulence to 20 near-isogenic lines that differ for leaf rust resistance genes. Populations that were geographically proximal were also more closely related for genotypes. In addition, groups of isolates within regions that varied for genotype were similar to groups from other regions, which indicated past and recent migration across regions. Isolates from tetraploid durum wheat in five different regions were highly related with distinct genotypes compared to isolates from hexaploid common wheat. Based on a molecular clock, isolates from durum wheat found only in Ethiopia were the first to diverge from a common ancestor form of P. triticina that is found on the wild wheat relative Aegilops speltoides, followed by the divergence of isolates found worldwide that are virulent to durum wheat, and then by isolates found on common wheat.