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

Jan Bettgenhaeuser,Brande B H Wulff,Inmaculada HernáNdez-PinzóN,Phon Green,Andrew M Dawson,John N Ferguson,Robbie Waugh,Jodie Taylor,Brian J Steffenson,Eric R Ward,Rosemary Bayles,Antonín Dreiseitl,Peter Emmrich,Matthew Smoker,Matthew Gardiner,Amelia Hubbard,Matthew J Moscou

doi:10.1038/s41467-021-27288-3

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.

Highlights

Crop losses caused by plant pathogens are a primary threat to stable food production
Puccinia striiformis only infected Triticeae species from which they were originally isolated. This host species specificity appeared to be common among diverse rust pathogens of grasses. These specialized forms, designated formae speciales, were later observed in several filamentous pathogen systems, such as the powdery mildews of cereals (Blumeria graminis)[4] and smuts (Ustilago spp.)[5] on the Triticeae, vascular wilt caused by Fusarium oxysporum[6], blast (Magnaporthe spp.) of grasses[7], the downy mildews (Bremia spp.) of Asteraceae[8], and white rusts (Albugo spp.) of Brassiceae[9]
DH lines that lack all three loci display a fully susceptible interaction similar to SusPtrit, whereas strong resistance in Golden Promise is recapitulated in DH lines that possess all three loci. These results demonstrate that a simple genetic architecture of three genes underlies resistance in Golden Promise: Rps[6] and Rps[7] confer resistance to early hyphal colonization, whereas Rps[8] restricts the pathogen during pustule formation

Summary

Introduction

Crop losses caused by plant pathogens are a primary threat to stable food production. These specialized forms, designated formae speciales, were later observed in several filamentous pathogen systems, such as the powdery mildews of cereals (Blumeria graminis)[4] and smuts (Ustilago spp.)[5] on the Triticeae, vascular wilt caused by Fusarium oxysporum[6], blast (Magnaporthe spp.) of grasses[7], the downy mildews (Bremia spp.) of Asteraceae[8], and white rusts (Albugo spp.) of Brassiceae[9] From these early observations of host adapted lineages in diverse plant-pathogen systems, considerable progress has been made in understanding the genetic architecture underlying resistance to non-adapted pathogens. The plant immune system is composed of successive layers of passive and active barriers that provide resistance to pathogens[12]

Methods

Results

Conclusion