The Keys to Controlling Wheat Rusts: Identification and Deployment of Genetic Resistance.

Abstract

Rust diseases are among the major constraints for wheat production worldwide due to the emergence and spread of highly destructive races of Puccinia. The most common approach to minimise yield losses due to rust is to use cultivars that are genetically resistant. Modern wheat cultivars, landraces, and wild relatives can contain undiscovered resistance genes, which typically encode kinase or nucleotide-binding site leucine rich repeat domain containing receptor proteins. Recent research has shown these genes can provide either resistance in all growth stages (all-stage resistance; ASR) or specially in later growth stages (adult-plant resistance; APR). ASR genes are pathogen and race-specific, meaning they can function against selected races of the rust fungus due to the necessity to recognise specific avirulence molecules in the pathogen. APR genes are either pathogen specific or multipathogen resistant but often race-nonspecific. Prediction of resistance genes through rust infection screening alone remains complex when more than one resistance gene is present. However, breakthroughs during the past half century such as single nucleotide polymorphism (SNP) based genotyping techniques and resistance gene isolation strategies such as MutRenSeq (Mutagenesis, Resistance gene enrichment and Sequencing), MutChromSeq (Mutagenesis and Chromosome Sequencing), and AgRenSeq (Association genetics combined with RenSeq) enable rapid transfer of resistance from source to modern cultivars. There is a strong need for combining multiple genes for better efficacy and longer-lasting resistance. Hence techniques such gene cassette creation speed up the gene combination process, but their widespread adoption and commercial use is limited due to their transgenic nature.