Wild plants can contribute valuable genes to their domesticated relatives, but reproductive barriers and a lack of genomic resources have long hindered the effective use of crop-wild gene introgression. Recently, an international research team led by the IPK Leibniz Institute achieved a major breakthrough by constructing the pan-genome of bulbous barley (Hordeum bulbosum), a close relative of barley. The research results were published in the journal Nature.
Wild relatives of cultivated plants are valuable resources for improving crop genetic diversity and resistance to biotic and abiotic stresses. Although their value has been known for decades, technical barriers have long restricted exploration. Now, advances in high-throughput genomic research have enabled the application of the same tools to both crops and their wild relatives.
The international research team focused on the structural genome evolution of barley (Hordeum vulgare) and bulbous barley (Hordeum bulbosum). First author of the study Jiawu Feng explained that Dr. Frank Blattner collected bulbous barley genotypes from natural populations in the Mediterranean region and combined them with genebank accessions to form a collection of 263 diverse genotypes, covering diploid and tetraploid cytotypes. After analyzing population structure, the team assembled and annotated ten chromosome-scale reference-quality bulbous barley genomes.
Feng noted that tetraploid bulbous barley has two centers of origin: one in Asia dating back one to two million years, and another in Greece that emerged only about 100,000 years ago. The two types are currently hybridizing, providing a pathway to enrich genomic diversity in polyploids. Although bulbous barley diverged from barley approximately 4.5 million years ago, their gene evolution differs markedly, with barley's genome having undergone expansion, primarily at the chromosome ends.
A common method for introducing genes from wild relatives into domesticated plants is the creation of introgression lines, which result from crosses between crops and their wild relatives and contain small segments of wild parent genomes in a cultivated plant background. Based on the reference genomes, the research group deciphered the structure of the Ryd4 resistance locus. This locus, introgressed from H. bulbosum into barley about 40 years ago, effectively resists the highly destructive barley yellow dwarf virus and is one of the most promising and the only near-commercialized crop-wild gene introgression in barley.
Dr. Martin Mascher, head of the Domestication Genomics research group at IPK, stated that having genome sequences of wild relatives of crops will help enable more targeted introgression breeding in the future. Professor Nils Stein, head of the Leibniz IPK Federal Ex Situ Genebank for Agricultural and Horticultural Crops, emphasized that the systematic genomic characterization of crops and their wild relatives is fundamental research that helps make more effective use of plant genetic resources for crop improvement and promotes the development of genebanks from seed banks into bio-digital resource centers.
