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United States Department of Agriculture

Agricultural Research Service

Research Project: CEREAL RUST FUNGI: GENETICS, POPULATION BIOLOGY, AND HOST-PATHOGEN INTERACTIONS

Location: Cereal Disease Laboratory

Title: Population divergence in the wheat leaf rust fungus Puccinia triticina is correlated with wheat evolution

Authors
item Liu, Miao
item Kolmer, James

Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 2, 2013
Publication Date: November 1, 2013
Citation: Liu, M., Kolmer, J.A. 2013. Population divergence in the wheat leaf rust fungus Puccinia triticina is correlated with wheat evolution. Molecular Phylogenetics and Evolution. 112:443-453.

Interpretive Summary: Wheat is attacked by the rust fungus called Puccinia triticina, which causes the disease wheat leaf rust. Durum wheat which is used to produce pasta products and common wheat, which is used to produced bread, cake and cookie products are attacked by different forms of the leaf rust fungus. Durum wheat predates common wheat, and is considered to be older in terms of evolution. The results of this study indicated that the forms of P. triticina that occur on a wild grass that is a durum wheat progenitor in Israel is the oldest form of leaf rust, and that a form that occurs on durum wheat only in Ethiopia is the second oldest form. The forms on common wheat were the most recent along with a form that occurred on durum wheat in Europe, Mexico, and the Middle East. In terms of evolution, the leaf rust fungus very recently adapted to the durum wheats that are grown in Europe, Mexico and the Middle East. These results indicated that P. triticina can adapt very quickly to wheat crops that are very different. These results will be used to further study the evolution and adaptation of the leaf rust fungus to wheat. These results will be used by plant pathologists and geneticists to further study the evolution and adaptation of the leaf rust fungus to wheat.

Technical Abstract: The objective of this study was to determine if the evolutionary history of the obligate pathogen on wheat, Puccinia triticina, is correlated with adaptation to hosts with different ploidy levels. Sequence data from 15 loci with different levels of polymorphism were generated. Phylogenetic analyses (parsimony, Bayesian, maximum likelihood) showed the divergence of four forms that correlated with host specificity and geographic locations: P. triticina from common hexaploid wheat (ABD genomes) found worldwide; P. triticina from cultivated tetraploid durum wheat (AB genomes) found worldwide; P. triticina from tetraploid durum wheat from Ethiopia and P. triticina from diploid Aegilops speltoides (B genome) that has been found only in Israel. Phylogenetic analyses and coalescence based genealogy samplers both indicated that P. triticina on diploid A. speltoides, the probable B genome donor of hexaploid wheat, diverged initially, followed by the Ethiopian durum wheat form and then by the common wheat form. P. triticina on worldwide cultivated durum wheat was the most recently coalesced form, which formed a clade nested within the common wheat form. By a relative time scale, the divergence of P. triticinia forms as delimited by host specificity appears very recent. Significant reciprocal gene flow between the common wheat form and the durum wheat form, and from the common wheat form to the Ethiopian durum form was detected.

Last Modified: 7/23/2014
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