Cytogenetic and molecular identification of a novel solid-stem wheat line carrying a T3JS·4JL translocation chromosome of Thinopyrum bessarabicum

Stem solidness is a key agronomic trait in wheat, conferring resistance to both lodging and infestation by the wheat stem sawfly ( Cephus cinctus Norton). This study reports the cytological and molecular characterization of a novel solid-stemmed wheat line, XX301, derived from a cross between common wheat ( Triticum aestivum L. cv. Chinese Spring, CS) and Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve. Cytogenetic analyses confirmed XX301 as a disomic addition line with 44 chromosomes, forming 22 bivalents at meiotic metaphase I. Genomic in situ hybridization (GISH) identified two alien chromosomes from Th. bessarabicum , which were further defined by oligonucleotide fluorescence in situ hybridization (FISH) as a pair of T3JS·4JL translocation chromosomes. This karyotypic structure was corroborated by InDel markers specific to chromosome arms 4JS (X27S3, X27S6) and 3JL (X27L4, X27L5), which amplified unique Th. bessarabicum fragments in XX301. Phenotypic evaluation revealed that the stem solidness of XX301 was comparable to that of the parental CS- Th. bessarabicum amphidiploid. Furthermore, crosses between XX301 and nine elite hollow-stemmed wheat germplasms produced F₁ progeny with completely solid stems, demonstrating the dominance of this trait and its potential for efficient introgression into breeding programs. The line XX301 thus represents a valuable genetic resource for improving stem solidness in wheat.