QTL for induced resistance against leaf rust in barley.

Leaf rust caused by is one of the major diseases of barley ( L.) leading to yield losses up to 60%. Even though, resistance genes 1 to 28 are known, most of these are already overcome. In this context, priming may promote enhanced resistance to . Several bacterial communities such as the soil bacterium (syn. ) are reported to induce resistance by priming. During quorum sensing in populations of gram negative bacteria, they produce -acyl homoserine-lactones (AHL), which induce resistance in plants in a species- and genotype-specific manner. Therefore, the present study aims to detect genotypic differences in the response of barley to AHL, followed by the identification of genomic regions involved in priming efficiency of barley. A diverse set of 198 spring barley accessions was treated with a repaired natural mutant strain + producing a substantial amount of AHL and a transformed strain carrying the lactonase gene from . For resistance the diseased leaf area and the infection type were scored 12 dpi (days post-inoculation), and the corresponding relative infection and priming efficiency were calculated. Results revealed significant effects (p<0.001) of the bacterial treatment indicating a positive effect of priming on resistance to . In a genome-wide association study (GWAS), based on the observed phenotypic differences and 493,846 filtered SNPs derived from the Illumina 9k iSelect chip, genotyping by sequencing (GBS), and exome capture data, 11 quantitative trait loci (QTL) were identified with a hot spot on the short arm of the barley chromosome 6H, associated to improved resistance to after priming with +. Genes in these QTL regions represent promising candidates for future research on the mechanisms of plant-microbe interactions.