AbstractGreenbug [Schizaphis graminum (Rondani)] is a destructive pest of wheat (Triticum aestivum L.) worldwide. Incorporation of wheat greenbug resistance genes in wheat‐breeding pipelines is critical to improve wheat production. The greenbug resistance gene Gb5, originally identified in Triticum speltoides chromosome 7S and transferred to wheat chromosome 7A, confers resistance to several economically important greenbug biotypes. The T. speltoides chromosome segment carrying Gb5 was previously shortened by means of homoeologous recombination induced by the ph1b gene, which minimized linkage drag and made Gb5 a useful gene for improvement of greenbug resistance in wheat. This study characterized the shortened T. speltoides chromosome segment in PI 603919 and developed kompetitive allele‐specific polymerase chain reaction (KASP) markers to facilitate its introgression in wheat breeding. A set of 21 simple sequence repeat (SSR) markers specific to wheat 7AL chromosome were developed to determine the length and location of the T. speltoides chromosome segment. The T. speltoides segment in PI 603919 was estimated to be about 79.5–87.8 Mb in the Chinese Spring reference sequence IWGSC RefSeq v.1.0. A recombinant inbred line (RIL) population derived from a cross between CI 17884, which carries the original wheat‐T. speltoides 7A‐7S translocation chromosome segment, and Bainong 418 was genotyped using the genotyping‐by‐sequencing (GBS) approach and evaluated for responses to greenbug biotype E. Three GBS‐derived single nucleotide polymorphisms (SNPs) on the shortened translocation segment were converted to KASP markers. These KASP markers were evaluated for efficacy to select Gb5 in wheat breeding.