The barley immune receptor Mla recognizes multiple pathogens and contributes to host range dynamics

Abstract

Crop losses caused by plant pathogens are a primary threat to stable food production. Stripe rust (Puccinia striiformis) is a fungal pathogen of cereal crops that causes significant, persistent yield loss. Stripe rust exhibits host species specificity, with lineages that have adapted to infect wheat and barley. While wheat stripe rust and barley stripe rust are commonly restricted to their corresponding hosts, the genes underlying this host specificity remain unknown. Here, we show that three resistance genes, Rps6, Rps7, and Rps8, contribute to immunity in barley to wheat stripe rust. Rps7 cosegregates with barley powdery mildew resistance at the Mla locus. Using transgenic complementation of different Mla alleles, we confirm allele-specific recognition of wheat stripe rust by Mla. Our results show that major resistance genes contribute to the host species specificity of wheat stripe rust on barley and that a shared genetic architecture underlies resistance to the adapted pathogen barley powdery mildew and non-adapted pathogen wheat stripe rust.

A lineage-specific Exo70 is required for receptor kinase–mediated immunity in barley

“…This host specialization shows evidence of durability, as Pst has been endemic for over 60 years in Australia, but has not undergone a host jump to barley despite both crops being grown in the same regions (26). Screening of diverse barley accessions has found that Pst is capable of infecting and reproducing on a small subset of barley accessions: primarily landraces and wild barley, as well as the hypersusceptible accession SusPtrit (27). Using a diverse panel of barley accessions, we previously identified three R gene loci designated Rps6, Rps7, and Rps8 as contributing to the nonadapted status of barley to Pst (27)(28)(29).…”

“…Using a diverse panel of barley accessions, we previously identified three R gene loci designated Rps6, Rps7, and Rps8 as contributing to the nonadapted status of barley to Pst (27)(28)(29). Rps8 was mapped to the long arm of chromosome 4H using a mapping population derived from SusPtrit × Golden Promise (SxGP) (27,30). In this work, we fine-mapped Rps8 to a 936-kb locus on chromosome 4H, which encompasses a presence/ absence variation across barley accessions.…”

Deep phenotyping platform for microscopic plant-pathogen interactions

“…Typically the plants are entirely immune against the non-adapted pathogens, e.g., barley is immune to Bgt and wheat to Bgh. However, some plant genotypes may allow microscopic growth of non-adapted pathogens, known as cryptic infection (Romero et al, 2018;Bourras et al, 2019;Bettgenhaeuser et al, 2021).…”

“…Typically the plants are entirely immune against the non-adapted pathogens, e.g., barley is immune to Bgt and wheat to Bgh. However, some plant genotypes may allow microscopic growth of non-adapted pathogens, known as cryptic infection (Romero et al ., 2018; Bourras et al ., 2019; Bettgenhaeuser et al ., 2021). The barley/wheat-powdery mildew model provides several advantages to the researchers: the fungus growth is fast and highly synchronized, the majority of the fungal biomass is located on the leaf surface, with straightforward to observe structures.…”

Postulation of Specific Disease Resistance Genes in Cereals: A Widely Used Method and Its Detailed Description

“…The primary importance of resistance genes is protecting barley against powdery mildew. However, their postulation has many other applications, including: (1) mapping the distribution of native resistance worldwide [ 13 , 14 , 15 ]; (2) the selection of genetic resources for crop breeding [ 16 , 17 ]; (3) the selection of well-characterized genotypes for evaluating partial resistance [ 18 ]; (4) assessing efficacy and expected durability of resistance of varieties including potential candidates for registration [ 19 ]; (5) description of new resistance in registered varieties [ 20 ]; (6) identifying varieties and confirming their authenticity and pedigrees [ 21 ]; (7) selection of differential varieties for studying pathogen populations [ 22 ] and their evolution [ 23 ]; (8) uncovering genotypic contamination [ 24 ]; and (9) basic research including the effect of Ml alleles on resistance to other pathogens [ 25 , 26 ].…”