Characterizing the Genetic Architecture of Nonhost Resistance in Barley Using Pathogenically Diverse Puccinia Isolates

Abstract

Barley is an intermediate or near-nonhost to many cereal rust pathogens that infect grasses, making it a highly suitable model to understand the evolution and genetic basis of nonhost resistance (NHR) in plants. To characterise the genetic architecture of NHR in barley, we used the Oregon Wolfe Barley doubled haploid (DH) and Morex x SusPtrit RIL mapping populations. To elicit a wide array of NHR responses, we tested 492 barley accessions and both mapping populations with pathogenically diverse cereal rust isolates representing distinct formae speciales adapted to Avena, Hordeum, Triticum and Lolium spp.: P. coronata f. sp. avenae (Pca; oat crown rust pathogen) and f. sp. lolii (Pcl; ryegrass crown rust pathogen); P. graminis f. sp. avenae (Pga; oat stem rust pathogen) and f. sp. lolii (Pgl; the ryegrass stem rust pathogen); and P. striiformis f. sp. tritici (Pst; wheat stripe rust pathogen) and f. sp. pseudo-hordei (Psph; barley grass stripe rust pathogen). With the exception of Pcl and Pca, susceptibility and segregation for NHR was observed in the barley accessions and both mapping populations. QTLs for NHR were mapped on all seven chromosomes. NHR in barley to the heterologous rusts tested was due to a combination of QTLs with either or both overlapping and distinct specificities. Across both mapping populations, broadly effective NHR loci were also identified that likely play a role in host specialisation.

Mapping of prehaustorial resistance against wheat leaf rust in einkorn (Triticum monococcum), a progenitor of wheat

“…Hence, a horizontal/race-independent resistance that has the character of nonhost resistance to leaf rust as a host-specific pathogen could be more durable. This nonhost–pathogen interaction was exemplarily described for barley— P. triticina ( Jafary et al., 2008 ; Haghdoust et al., 2021 ) and wheat— Blumeria hordei , P. hordei , and Magnaporthe oryzae ( Delventhal et al., 2017 ). Nonhost interactions result in prehaustorial resistance (phr) and have also been observed in T. monococcum–P.…”

Trends and Perspectives for the Use of Crop Wild Relatives in Crop Breeding

“…Hence, a horizontal/race-independent resistance that has the character of nonhost resistance to leaf rust as a host-specific pathogen could be more durable. This nonhost-pathogen interaction was exemplarily described for barley-P. triticina (Jafary et al, 2008;Haghdoust et al, 2021) and wheat-Blumeria hordei, P. hordei, and Magnaporthe oryzae (Delventhal et al, 2017). Nonhost interactions result in prehaustorial resistance (phr) and have also been observed in T. monococcum-P. triticina interactions (Serfling et al 2016;Anker et al 2001;Anker and Niks, 2001).…”

Genetic approaches to dissect plant nonhost resistance mechanisms

“…One common strategy for using near‐hosts to understand NHR is to find intraspecific or interspecific variation in NHR and identify genes underlying the differences through genetic mapping. For example, in a recent report, Haghdoust et al ( 2021 ) tested 492 barley accessions and two mapping populations with pathogenically diverse cereal rust ( Puccinia ) isolates representing distinct formae speciales adapted to different cereal species. The authors found that about 80% of the barley accessions were either immune or near immune to all pathogens tested and identified major quantitative trait loci (QTLs) in barley that may contribute to NHR (Haghdoust et al, 2021 ).…”

“…For example, in a recent report, Haghdoust et al ( 2021 ) tested 492 barley accessions and two mapping populations with pathogenically diverse cereal rust ( Puccinia ) isolates representing distinct formae speciales adapted to different cereal species. The authors found that about 80% of the barley accessions were either immune or near immune to all pathogens tested and identified major quantitative trait loci (QTLs) in barley that may contribute to NHR (Haghdoust et al, 2021 ). These observations support the notion that there is a continuum between NHR and host resistance, and in some cases the resistance phenotypes are quantitative traits (Bettgenhaeuser et al, 2014 ).…”