Molecular cytogenetic identification of two wheat–Thinopyrum ponticum substitution lines conferring stripe rust resistance

Distant hybridizations are important for developing common wheat germplasm. Thinopyrum ponticum (2n = 10x = 70), which is a wild relative of wheat, has numerous advantages for enhancing the tolerance of plants to biotic and abiotic stresses. ES-11 and ES-12 are two stable lines derived from a cross between the Triticum aestivum–Th. ponticum partial amphiploid line Xiaoyan784 (2n = 8x = 56) and the wheat Abbondanza nullisomic lines (2n = 40) involving consecutive self-crosses and cytological marker-assisted selection. Lines ES-11 and ES-12 were characterized by a cytogenetic analysis, a sequential fluorescence in situ hybridization (FISH)–genomic in situ hybridization (GISH), and a multicolor GISH (mc-GISH) combined with an analysis of functional molecular markers. Moreover, their agronomic traits and disease resistance were evaluated. The cytogenetic results suggested that ES-11 and ES-12 contained 42 chromosomes. In ES-12, wheat chromosome 3D was replaced by a pair of Th. ponticum 3St chromosomes for a genome composition of 14A + 14B + 12D + 2(3St). In ES-11, wheat chromosome 3B and 4D were replaced by chromosomes 3St and 4 J, respectively, for a genome composition of 14A + 12B + 12D + 2(3St) +2(4J). The detected recombination between chromosomes 3St and 4J and the structural variation of chromosome 2A were due to the introduction of two pairs of Th. ponticum chromosomes. Additionally, ES-11 and ES-12 were resistant to stripe rust at the seedling and adult stages. Thus, the highly disease-resistant wheat–Th. ponticum disomic substitution line (ES-12) and double substitution line (ES-11) are potentially useful germplasms for breeding disease-resistant wheat lines.