QTL for induced resistance against leaf rust in barley

Area of Science:

• Plant pathology
• Microbial ecology
• Genetics

Background:

• Leaf rust, caused by *Puccinia hordei*, significantly reduces barley (*Hordeum vulgare*) yield.
• Existing resistance genes are often overcome, necessitating alternative resistance strategies like priming.
• Bacterial quorum sensing molecules, specifically *N*-acyl homoserine-lactones (AHLs), can induce plant resistance.

Purpose of the Study:

• To investigate genotypic variation in barley's response to AHL-mediated priming.
• To identify genomic regions in barley associated with enhanced resistance to *P. hordei* after priming.
• To explore the potential of bacterial priming for durable disease resistance in barley.

Main Methods:

• Treatment of 198 spring barley accessions with *Ensifer meliloti* strains engineered for AHL production or degradation.
• Phenotypic evaluation of leaf rust severity (diseased leaf area, infection type) 12 days post-inoculation.
• Genome-wide association study (GWAS) using SNP data to identify quantitative trait loci (QTL) linked to priming efficiency.

Main Results:

• Bacterial treatment significantly improved barley resistance to *P. hordei* (p<0.001), demonstrating effective priming.
• Eleven QTL associated with enhanced *P. hordei* resistance were identified, with a hotspot on barley chromosome 6H.
• The identified QTL regions contain candidate genes potentially involved in plant-microbe interactions and priming.

Conclusions:

• Bacterial priming using AHLs is a viable strategy to enhance barley resistance against leaf rust.
• The identified QTL on chromosome 6H provide targets for breeding improved disease-resistant barley varieties.
• Further research into the identified candidate genes can elucidate mechanisms of priming-induced resistance.