Barley (Hordeum vulgare) ranks as the world’s fourth most widely cultivated cereal crop, making it a valuable object for genetic research [1]. Understanding barley inflorescence development is crucial for improving grain yield and creating new varieties [2]. During the pinnacle of mutational breeding, a large collection of mutants that have no direct economic value but are interesting as a source for genetic mapping and gene function identification were created [3]. About 50 years ago, a series of barley developmental mutants were created using chemical mutagenesis at Vilnius University Department of Botany and Genetics. These mutants feature gradient inflorescence development and spikelet-free gaps in spikes, hyperdeveloped spike tips, and the most interesting feature is genome instability in the remote generations [4]. Genetic mapping of tw (tweaky spike) mutants can offer new insights into barley inflorescence development.
This study aimed to explore the genetic background of barley tw phenotype by creating two F\(_{2}\) recombinant populations possessing the tw phenotype, tw x WT (tw-rF\(_{2}\)) and tw\(_{2}\) x WT (tw\(_{2}\)-rF\(_{2}\)). Segregation analysis revealed tw mutation to be monogenic. To identify candidate genes responsible for the tw phenotype, whole genome sequencing was performed on WT, tw-rF\(_{2}\) and tw\(_{2}\)-rF\(_{2}\). SNP ratio analysis determined the same non-recombinant region in both populations, tw-rF\(_{2}\) had 65 genes with deleterious mutations, whereas tw\(_{2}\)-rF\(_{2}\) had 27 genes. 7 genes with deleterious mutations were common between both populations: 2 of them were already annotated, 3 – SIFT [5] algorithm predicted as tolerated substitutions, 1 gene with exon deletion (candidate gene 1) and 1 gene with whole gene deletion (candidate gene 2). Two candidate genes were later investigated in other tw allelic mutants (tw\(_{1}\), tw\(_{4}\), tw\(_{5}\), tw\(_{6}\), tw\(_{8}\), tw\(_{9}\), tw\(_{10}\)) using Sanger sequencing. Only one candidate gene (2) had disrupted gene function in all allelic mutants, making it responsible for the tw phenotype. This hypothesis will be validated by creating gene knockout in WT later on. This research was was supported by the Research Council of Lithuania (LMTLT) under grant No. P-MIP-24-109 “Genetic mapping and characterization of barley developmental flower/inflorescence tweaky spike (tw) mutation”