Evaluation of Barley—Introgression Lines Between Annual Barley and the Perennial Hordeum bulbosum in a Cold-Temperate Climate

Perennial wild relatives of annual crops possess traits associated with stress tolerance, efficient nutrient uptake, and increased soil carbon sequestration. They therefore represent valuable genetic resources for developing perennial crops that may reduce environmental and climate impacts and enhance food security. We evaluated 151 introgression lines (ILs) derived from crosses between barley and the perennial relative Hordeum bulbosum, each carrying unique H. bulbosum chromosome segments in a barley genetic background. Growth and regrowth after harvest were evaluated in two field trials, established by spring and fall planting in separate years in central Sweden, and under simulated two-year seasonal cycles in a climate chamber. In the climate chamber, 54% of the ILs exhibited strong regrowth, and two-thirds of these ILs showed reproductive growth across two seasonal cycles. In the field, most ILs showed regrowth after harvest but did not survive the cold winter. The parental genetic background had a strong effect from the barley parent on several growth and reproductive traits, but some ILs exhibited phenotypes not expected based on the barley parent. Of the divergent ILs with high regrowth, identified by PCA combining all studied traits, H. bulbosum introgressions at chromosome arms 2HL and 4HL were highly represented among ILs with cultivar Emir as a barley parent, and introgressions at 1HL among ILs with cultivar Morex as a parent. Perennial growth was observed only under mild conditions, indicating that perenniality of these ILs in a cold-temperate climate requires not only regrowth capacity but also adaptation to photoperiod, vernalization, and frost. ILs with high regrowth and reproductive growth may be used in crossing efforts with cold-tolerant germplasm to support the development of perennial barley.