Virulence Characterization of Wheat Stripe Rust Fungus Puccinia striiformis f. sp. tritici in Ethiopia and Evaluation of Ethiopian Wheat Germplasm for Resistance to Races of the Pathogen from Ethiopia and the United States

Abstract

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most important diseases of wheat in Ethiopia. In total, 97 isolates were recovered from stripe rust samples collected in Ethiopia in 2013 and 2014. These isolates were tested on a set of 18 Yr single-gene differentials for characterization of races and 7 supplementary differentials for additional information of virulence. Of 18 P. striiformis f. sp. tritici races identified, the 5 most predominant races were PSTv-105 (21.7%), PSTv-106 (17.5%), PSTv-107 (11.3%), PSTv-76 (10.3%), and PSTv-41 (6.2%). High frequencies (>40%) were detected for virulence to resistance genes Yr1, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, Yr27, Yr28, Yr31, Yr43, Yr44, YrExp2, and YrA. Low frequencies (<40%) were detected for virulence to Yr10, Yr24, Yr32, YrTr1, Hybrid 46, and Vilmorin 23. None of the isolates were virulent to Yr5, Yr15, YrSP, and YrTye. Among the six collection regions, Arsi Robe and Tiyo had the highest virulence diversities, followed by Bekoji, while Bale and Holeta had the lowest. Evaluation of 178 Ethiopian wheat cultivars and landraces with two of the Ethiopian races and three races from the United States indicated that the Ethiopian races were more virulent on the germplasm than the predominant races of the United States. Thirteen wheat cultivars or landraces that were resistant or moderately resistant to all five tested races should be useful for breeding wheat cultivars with resistance to stripe rust in both countries.

Stripe rust resistance genes in a set of Ethiopian bread wheat cultivars and breeding lines

“…We identified 14 breeding lines and two cultivars that were resistant to all races. Wan et al (2017) also identified several genotypes resistant at the seedling stage among the tested material, using two additional Pst races from Ethiopia and three from the United States.…”

“…The seedlings were then transferred to a growth chamber with 16 h day at 16°C and 8 h night at 13°C. Six Chinese and one Ethiopian stripe rust races (culture EK3-12, Wan et al 2017) were used in the study. The virulence: avirulence profiles of the actual isolates of those races are given in Table 1.…”

Genome‐wide mapping of resistance to stripe rust caused by Puccinia striiformis f. sp. tritici in hexaploid winter wheat

“…( Pst ), the causal agent of wheat stripe rust, is a serious threat to global wheat production (Boyd, 2005; Chen, 2005; Wellings, 2011). Virulence shifts in Pst population due to the genetic changes in existing local pathogen populations or migration of new races are major challenges to resistance breeding in wheat (Burdon, Barrett, Rebetzke, & Thrall, 2014; Chen, 2007; Hovmøller, Sørensen, Walter, & Justesen, 2011; Wan & Chen, 2014; Wan et al., 2016). Nearly US$1 billion is lost to Pst annually (Beddow et al., 2015).…”

Characterizing and Validating Stripe Rust Resistance Loci in US Pacific Northwest Winter Wheat Accessions (Triticum aestivum L.) by Genome‐wide Association and Linkage Mapping

“…The post‐2000 group of Pst races has broad‐spectrum virulence and increased aggressiveness and adaptation in warmer environments (Markell and Milus, 2008; Milus et al, 2009; Chen et al, 2010). In the US PNW, new races have been identified every year and race compositions are more diverse than any other region of the U.S. (Chen et al, 2010; Wan and Chen, 2012, 2014; Wan et al, 2017). Historically, PNW wheat breeders have incorporated multiple resistance genes for all‐stage resistance and adult‐plant resistance (APR) to develop more durable rust resistant wheat cultivars.…”