Agricultural Research Service Cereal Disease Laboratory

Saint Paul, MN, United States

Agricultural Research Service Cereal Disease Laboratory

Saint Paul, MN, United States
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Ordonez M.E.,Agricultural Research Service Cereal Disease Laboratory | German S.E.,Instituto Nacional Of Investigacion Agropecuraria | Kolmer J.A.,Agricultural Research Service Cereal Disease Laboratory
Phytopathology | Year: 2010

Leaf rust, caused by Puccinia triticina, is the most prevalent and widespread disease of wheat in South America. The objective of this study was to determine whether genetically differentiated groups of P. triticina are currently present in South America and to compare the South American population with the previously characterized population in North America. In total, 130 isolates of P. triticina from the wheatgrowing regions of Argentina, Brazil, Chile, Peru, and Uruguay, mostly from the 1990s to 2008, were tested for virulence on 20 lines of wheat with single genes for leaf rust resistance and for molecular genotypes with 23 simple-sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotypes, 99 isolates were included for further analysis. Principal coordinate analysis plots indicated five different groups of isolates based on SSR genotypes that also differed for virulence to leaf rust resistance genes. All pairs of groups, except for one pair, were significantly differentiated for SSR genotypes according to RST statistics. All but two pairs of groups were significantly differentiated for virulence phenotype according to φPT statistics. Isolates in all five groups had high values of fixation index for SSR alleles and linkage disequilibrium was high across all isolates that indicated the clonal reproduction of urediniospores. Only one of the five P. triticina groups from South America was differentiated for SSR genotypes from all of the six P. triticina groups from North America. The high degree of similarity for SSR genotype of isolates from both South America and North America suggested a common European origin of P. triticina that was introduced to both continents. The emergence of the same P. triticina virulence phenotypes with highly related SSR genotypes in the United States in 1996 and in Uruguay in 1999 indicated the likely intercontinental migration of these genotypes from Mexico to both South America and North America. © 2010 The American Phytopathological Society.


Lysoe E.,Norwegian Institute for Agricultural And Environmental Research Bioforsk | Pasquali M.,University of Minnesota | Pasquali M.,Center De Recherche Public Gabriel Lippmann | Breakspear A.,University of Minnesota | And 2 more authors.
Molecular Plant-Microbe Interactions | Year: 2011

Fusarium graminearum is an important plant-pathogenic fungus and the major cause of cereal head blight. Here, we report the functional analysis of FgStuA, the gene for a transcription factor with homology to key developmental regulators in fungi. The deletion mutant was greatly reduced in pathogenicity on wheat heads and in production of secondary metabolites. Spore production was significantly impaired in ΔFgStuA, which did not develop perithecia and sexual ascospores, and lacked conidiophores and phialides, leading to delayed production of aberrant macroconidia. FgStuAp appears to act as a global regulator that may affect many diverse aspects of the life cycle of F. graminearum. Transcriptome analysis shows that thousands of genes are differentially expressed in the mutant during asexual sporulation and infection of wheat heads and under conditions that induce secondary metabolites, including many that could account for the mutant phenotypes observed. The primary regulatory targets of FgStuAp are likely genes involved in cell-cycle control, and the predicted FgStuAp sequence has an APSES domain, with homology to helixloop- helix proteins involved in cell-cycle regulation. The Aspergillus StuAp response element (A/TCGCGT/ANA/C) was found highly enriched in the promoter sequences of cellcycle genes, which was upregulated in the ΔFgStuA deletion mutant. © 2011 The American Phytopathological Society.


Kolmer J.A.,Agricultural Research Service Cereal Disease Laboratory | Hughes M.E.,Agricultural Research Service Cereal Disease Laboratory
Plant Disease | Year: 2014

Collections of Puccinia triticina were obtained from rust-infected leaves provided by cooperators throughout the United States and from wheat fields and breeding plots by United States Department of Agriculture- Agricultural Research Service personnel and cooperators in the Great Plains, Ohio River Valley, southeastern states, and Washington State and Idaho in order to determine the virulence of the wheat leaf rust population in 2012. Single uredinial isolates (501 in total) were derived from the collections and tested for virulence phenotype on 20 lines of 'Thatcher' wheat that are near-isogenic for leaf rust resistance genes. In 2012, 74 virulence phenotypes were described in the United States. Virulence phenotypes TNBGJ, TCRKG, and MBTNB were the three most common phenotypes. Phenotype TNBGJ is virulent to Lr39/41 and was widely distributed throughout the hard red winter wheat region of the Great Plains. Phenotype TCRKG is virulent to Lr11, Lr18, and Lr26 and was found mostly in the soft red winter wheat region in the eastern United States. Phenotype MBTNB is virulent to Lr11 and was also found mostly in the soft red winter wheat region. The frequency of isolates with virulence to Lr39/41, which is present in many hard red winter wheat cultivars in the Great Plains region, continued to increase. Isolates with virulence to Lr21, which is present in many hard red spring wheat cultivars, also continued to increase in frequency in the northern Great Plains region. © 2014 The American Phytopathological Society.


Kolmer J.A.,Agricultural Research Service Cereal Disease Laboratory | Long D.L.,Agricultural Research Service Cereal Disease Laboratory | Hughes M.E.,Agricultural Research Service Cereal Disease Laboratory
Plant Disease | Year: 2011

Agricultural Research Service personnel in the Great Plains, Ohio River Valley, southeast, California, and Washington State in order to determine the virulence of the wheat leaf rust population in 2009. Single uredinial isolates (591 in total) were derived from the collections and tested for virulence phenotype on lines of Thatcher wheat that are near-isogenic for leaf rust resistance genes Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr16, Lr24, Lr26, Lr3ka, Lr11, Lr17a, Lr30, LrB, Lr10, Lr14a, Lr18, Lr21, and Lr28 and a winter wheat line with Lr39/41. Forty-one virulence phenotypes were described. Virulence phenotypes MLDSD, TCRKG, and TDBGG were the three most common phenotypes. Phenotype MLDSD is virulent to Lr17 and Lr39/Lr41 and was widely distributed throughout the United States. Phenotype TCRKG is virulent to Lr11, Lr18, and Lr26 and is found mostly in the soft red winter wheat region in the eastern United States. TDBGG is virulent to Lr24 and was found in both the soft red winter wheat and hard red winter wheat regions. Virulence to Lr21 was not found in any of the tested isolates. Virulence to Lr11, Lr18, and Lr26 increased in 2009 in the soft red winter wheat regions. Virulence to Lr17 and Lr39/Lr41 increased in the Great Plains region. Two separate epidemiological zones of P. triticina in the soft red winter wheat region of the southern and eastern states and in the hard red wheat region of the Great Plains were described.

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