Priming Is a Suitable Strategy to Enhance Resistance Towards Leaf Rust in Barley

Priming allows plants to respond faster and stronger to abiotic or biotic stresses. Leaf rust (Puccinia hordei) is an important pathogen of barley (Hordeum vulgare), for which resistance genes are known, but mostly overcome. Therefore, the aims of this study were (i) to establish a priming system in barley, based on bacterial N-acyl homoserine lactone (AHL), and (ii) to get information on the effect of priming on the reaction to leaf rust. Plants were inoculated with bacteria, i.e., Ensifer meliloti with repaired expR copy, producing the oxo-C14-homoserine lactone (AHL) and an E. meliloti strain carrying the attM lactonase gene from Agrobacterium tumefaciens, which cleaves the AHL and acts here as negative control. After three bacterial inoculations, plants were challenged with P. hordei strain I-80 at the three leaves stage. Twelve days after infection, scoring of the leaf area diseased and the infection type was conducted followed by the calculation of the relative susceptibility. First results indicate a significantly (P < 0.001) higher resistance level to P. hordei after inoculation with E. meliloti. Furthermore, significant (P < 0.001) differences were detected between the accessions tested for priming efficiency, which can be the basis to screen a larger set of barley accessions to detect quantitative trait loci or candidate genes involved in priming.