triticina populations from North America ( Ordoñez and Kolmer 2009), South America ( Ordoñez et al. Department of Agriculture Agricultural Research Service (USDA-ARS) Cereal Disease Laboratory, P. triticina populations between different continental regions. Although there is considerable knowledge regarding genetic variation within different continental regions, no previous study has examined the genetic relationship and diversity of P. triticina are conducted in the United States ( Kolmer and Hughes 2017) and Canada ( McCallum and Seto-Goh 2006), which provide immediate information to help inform and support breeding programs in the selection of resistant wheat germplasm. triticina have been examined for molecular variation and virulence in numerous studies. 1980) and parts of West Asia ( Tatlidil et al. The native habitat of the most compatible alternate host (pycnial-aecial spore stages), Thalictrum speciosissimum L., is limited to southern Europe ( Casulli 1988 Casulli and Siniscalco 1987 Sibilia et al. triticina is a heteroecious rust, an alternate host is required for completion of the sexual cycle. Clonal reproduction of urediniospores occurs on the uredinial-telial hosts. The principal uredinial-telial hosts are hexaploid common wheat ( Triticum aestivum L.), tetraploid durum wheat ( T. 1992 Saari and Prescott 1985 Samborski 1985). Puccinia triticina Erikss., the wheat leaf rust fungus, is found throughout most of the nonarid wheat production areas of the world ( Roelfs et al. 2019), in addition to being transported over long distances by human activities ( Park et al. Other types of fungal pathogens, such as rust fungi, have infective spores that are adapted for wind dissemination over thousands of kilometers ( Kolmer 2005 Visser et al. Pathogen distribution is affected by human activities, as in the case of Cryphonectria parasitica, the chestnut blight fungus, and Ophiostoma ulmi, the Dutch elm disease fungus, both of which were introduced to North America in the last century by transport of infected plant material from Europe ( Brown and Hovmøller 2002). Fungal pathogens have achieved this in various ways, depending on their means of dispersal. 2015) and also to exploit the genetic uniformity of many host populations in human-guided agricultural production systems.
The wide distribution is evidence of the ability of fungal plant pathogens to adapt to natural host environments ( Gladieux et al. Among crop pathogens and pests, fungal pathogens have the lowest rate of regional endemicity at 5.8% and are the leading category of global plant pathogen invaders ( Bebber et al. Although fungi have the narrowest host range of various pathogens and pests, they have the highest saturation rate (the number of countries where the pathogen or pest was found/the number of countries where the pathogen or pest could be present based on host population) compared with other pathogens and insect pests. Plant pathogenic fungi in particular are distributed across different continents and are rarely endemic to only one country or continental region ( Bebber et al.
Many important plant pathogens and pests are widespread throughout the major agricultural and ecological regions of the world. triticina indicated past and more recent migration events facilitated by the spread of clonally produced urediniospores. The wide geographic distribution of identical and highly related multilocus genotypes of P. Twenty-seven multilocus genotypes were found in more than one continental region, and 13 of these had isolates with identical virulence phenotypes. The populations from North America and South America, Central Asia and Russia, and the Middle East and Europe were closely related for multilocus genotypes and many individual isolates from other continental regions were closely related.
All populations had high heterozygosity and significant correlation between virulence and molecular variation, which indicated clonal reproduction. A total of 424 multilocus genotypes and 497 virulence phenotypes were found. A total of 831 single-uredinial isolates collected from 11 regions were characterized for multilocus genotype at 23 simple sequence repeat loci and for virulence to 20 lines of wheat with single genes for leaf rust resistance. triticina in different worldwide regions. The objective of this research was to determine the genetic relatedness of P. Puccinia triticina, the wheat leaf rust fungus, is a major pathogen in many wheat production areas of the world. Many plant pathogenic fungi have a global distribution across diverse ecological zones and agricultural production systems.
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