Cytogenetic characterization and molecular marker development of a novel wheat-Thinopyrum ponticum 5E (5D) disomic substitution line with resistance to powdery mildew and stripe rust

Thinopyrum ponticum (2n=10x=70), a wild relative of common wheat (Triticum aestivum L.), is considered an invaluable genetic resource for wheat improvement due to its abundance of genes that confer resistance to biotic and abiotic stresses. This study focused on the CH97 line, derived from the BC1F7 progeny of a cross between wheat cv. 7182 and Th. ponticum. Cytological evidence showed that CH97 has 42 chromosomes, forming 21 bivalents at meiotic metaphase I, with the bivalents subsequently separating and moving to opposite poles during meiotic anaphase I. Through a combination of FISH (fluorescence in situ hybridization), GISH (genomic in situ hybridization), mc-GISH (multicolor genomic in situ hybridization), and liquid array analysis, it was determined that CH97 comprises 40 wheat chromosomes and two alien chromosomes from the Ee genome of Th. ponticum, featuring the absence of a pair of 5D chromosomes and variations in 1B, 6B, and 7B chromosomes. These findings confirm that CH97 is a stable wheat-Th. ponticum 5E (5D) alien disomic substitution line. Inoculation experiments revealed that CH97 exhibits high resistance to wheat powdery mildew and stripe rust throughout the growth period, in contrast to the highly susceptible common wheat parent 7182. Compared to 7182, CH97 displayed improvements in spikelets per spike, thousand-kernel weight, and kernel length. Additionally, utilizing SLAF-seq technology, chromosome 5E-specific molecular markers were developed and validated, achieving a 33.3% success rate, which facilitates marker-assisted selection to enhance disease resistance in wheat. Overall, the CH97 substitution line, with its resistance to diseases and improved agronomic traits represents valuable new germplasm for wheat chromosome engineering and breeding.