Genotyping-by-Sequencing Uncovers a Thinopyrum 4St.1Jvs Robertsonian translocation Linked to Multiple Stress Tolerances in bread wheat

Agropyron glael, a hybrid derived from Thinopyrum intermedium and Th. ponticum, serves as a valuable genetic resource for enhancing rust resistance in wheat. Despite its potential, limited knowledge of its chromosome structure and homoeologous relationships with hexaploid wheat has restricted the full exploitation of A. glael's genetic diversity in breeding programs. In this study, we present the development of a 44-chromosome wheat/A. glael addition line (GLA7). Multicolor genomic in situ hybridization identified one chromosome arm from the St genome, while the other arm remained unclassified, showing FISH patterns that did not align with any known wheat chromosomes.Genotyping-by-sequencing (GBS) read coverage analysis revealed a unique Robertsonian translocation between two distinct Thinopyrum subgenomes, identified as 4StS.1JvsS. Additionally, GBS analysis indicated that the Thinopyrum subgenomes in A. glael have a closer relationship with the D genome of wheat than with the A and B genomes, alongside notable differences in read densities along the wheatgrass in silico chromosomes, and a 47 Mb deletion in the wheat crossing partner.The GLA7 line demonstrated strong adult-plant resistance to both leaf rust and stripe rust under natural and artificial infection conditions. Automated phenotyping of drought stress prior to flowering showed that the GLA7 line exhibited greater tolerance compared to its wheat genotypes. In field trials, the GLA7 maintained yield-determining traits on par with the wheat parents.This unique addition line holds promise for enhancing wheat's tolerance to multiple stresses through the introduction of new resistance genes, as well as its ability to mitigate the effects of temporary water limitation during flowering, all without negatively impacting wheat performance.