Virulence characterization of Puccinia striiformis f. sp. tritici collections from six countries in 2013 to 2020

Abstract

Puccinia striiformis f. sp. tritici (Pst) causes wheat stripe rust (also called yellow rust, Yr), one of the most important diseases worldwide. Characterization of virulence in Pst populations is essential for developing wheat cultivars with effective and durable resistance to control the disease. A total of 138 Pst races, including 120 races that were not previously reported, were identified from stripe rust collections made from Canada, China, Ecuador, Egypt, Italy and Mexico in 2013-2020 using a set of 18 Yr single-gene differentials. Virulence of the resistance gene Yr5 or Yr15 was not found in isolates from any of the countries, indicating their effectiveness against the Pst populations. Virulence to 16 Yr genes was detected, but the frequencies varied greatly among countries. On average, the frequencies of virulence to Yr6, Yr7, Yr9, Yr43, Yr44 and YrExp2 were high (81.7-90.6%), those to Yr1, Yr8, Yr17, Yr27, YrSP and Yr76 were moderate (34.0-56.8%), and those to Yr10, Yr24, Yr32 and YrTr1 were low or very low (0.4-18.5%). The same races detected in different countries and different races from different countries clustered into the same virulence groups, indicating Pst migration among different countries, especially between eastern Asia and the Mediterranean region. These results should be useful for breeding wheat cultivars with effective resistance to stripe rust in these countries as well as globally.

Molecular Characterization of Wheat Stripe Rust Pathogen (Puccinia striiformis f. sp. tritici) Collections from Nine Countries

“…The stripe rust pathogen is distributed in the wheat-growing countries throughout the world, and the fungus evolves and disseminates rapidly from one country to another [9][10][11][13][14][15]21,26,32,33]. The present study successfully tested the hypothesis that Pst migrates among countries and continents, which was proposed based on the virulence data of the collections from different countries in a recent study [52]. Our study offers clear evidence supporting Pst migration around the global.…”

“…The overall correlation coefficient value (0.235) between the molecular genotype data and the previously published virulence data [51,52] was low, but significant. This value is lower than the 0.41 value reported for the international collections from 2006 to 2010 [26].…”

“…The specific objectives of this study were to (1) characterize the international collections of Pst since 2010 using SSR markers and identify molecular groups, (2) determine and compare the levels of genetic diversities, heterozygosity, and differentiation among different molecular groups and countries, and (3) track migrations among Pst populations among different countries. Using the molecular data, we also inferred reproduction mode and the correlation between the molecular data and previously published virulence data [51,52]. The results should provide a better understanding of stripe rust epidemiology and distribution, and the migration of the pathogen populations, as well as mechanisms of pathogen evolution.…”

“…Correlation analysis was conducted with the marker data obtained from this study and the virulence data of a separate study [52] using Mantel tests with 1000 permutations. When all isolates were considered without any grouping, the overall correlation coefficient was 0.235 (P < 0.001) between the marker genotypes and virulence phenotypes (Tables 6 and 7), indicating a low but significant correlation between the two data sets.…”

“…To determine the correlations between the molecular data obtained in the present study with the virulence data in a previous study from our group [52], a distance matrix was generated for each country population with each of the two data sets using GenAlEx 6.5 [78]. The regression analysis was used to obtain the correlation coefficient based on the distance matrix generated from the two datasets, and the significance of correlation was determined using P = 0.05.…”