Characterisation of barley resistance to rhynchosporium on chromosome 6HS

Key Message: Major resistance gene to rhynchosporium, Rrs18, maps close to the telomere on the short arm of chromosome 6H in barley. Rhynchosporium or barley scald caused by a fungal pathogen Rhynchosporium commune is one of the most destructive and economically important diseases of barley in the world. Testing of Steptoe × Morex and CIho 3515 × Alexis doubled haploid populations has revealed a large effect QTL for resistance to R. commune close to the telomere on the short arm of chromosome 6H, present in both populations. Mapping markers flanking the QTL from both populations onto the 2017 Morex genome assembly revealed a rhynchosporium resistance locus independent of Rrs13 that we named Rrs18. The causal gene was fine mapped to an interval of 660 Kb using Steptoe × Morex backcross 1 S₂ and S₃ lines with molecular markers developed from Steptoe exome capture variant calling. Sequencing RNA from CIho 3515 and Alexis revealed that only 4 genes within the Rrs18 interval were transcribed in leaf tissue with a serine/threonine protein kinase being the most likely candidate for Rrs18.Max Coulter, Bianca Büttner, Kerstin Hofmann, Micha Bayer, Luke Ramsay, Günther Schweizer, Robbie Waugh, Mark E. Looseley, Anna Avrov

Novel genes from wild barley hordeum spontaneum for barley improvement

Narrowing genetic basis is the bottleneck for modern plant improvement. Genetic variation in wild barley Hordeum spontaneum is much greater than that of either cultivated or landrace H. vulgare gene pool. It represents a valuable but underutilised gene pool for barley improvement as no biological isolation barriers exist between H. spontaneum and cultivated barley. Novel sources of new genes were identified from H. spontaneum for yield, quality, disease resistance and abiotic tolerance. Quantitative trait loci (QTLs) were mapped to all barley chromosomes. A QTL on chromosome 4H from the wild barley consistently increased yield by 7.7% across six test environments. Wild barley H. spontaneum was demonstrated as key genetic resource for drought and salinity tolerance. Two QTLs on chromosomes 2H and 5H increased grain yield by 12–22% under drought conditions. Several QTL clusters were present on chromosomes 1H, 2H, 4H, 6H and 7H from H. spontaneum for drought and salinity tolerance. Numerous candidate genes were identified to associate with tolerance to drought or salinity, and some of the candidate genes co-located with the QTLs for drought tolerance. QTLs/genes for resistance to powdery mildew, leaf rust and scald were mapped to all chromosomes. Scald resistance was found in at least five chromosome locations (1HS, 3H, 6HS, 7HL and 7HS) from H. spontaneum, and simple molecular markers were developed to accelerate transferring of these genes into cultivated barley. Novel beta-amylase allele from H. spontaneum was used to improve barley malting quality. Advanced backcross QTL provides an efficiency approach to transfer novel genes from H. spontaneum to cultivated barley