Cytogenetic characterization of a novel wheat-rye 2R (2D) substitution line YT9 conferring powdery mildew resistance from the three-leaf stage and physical mapping of PmYT9

Abstract

A wheat-rye 2R (2D) substitution line with PmYT9 conferring powdery mildew resistance was characterized. PmYT9 was mapped to a 14. 55 Mb interval on 2RL. A homozygous translocation line carrying PmYT9 was developed. Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), poses a significant threat to wheat (Triticum aestivum L.) production. The identification and utilization of novel resistance genes from wheat relatives are an effective strategy for sustainable disease management. Rye (Secale cereale L. RR), a tertiary gene pool of wheat, harbors abundant genetic diversity. In this study, we developed a novel wheat-rye derivative line, YT9, by crossing hexaploid triticale 09R1-16 with wheat breeding line PB9. Genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and agronomic trait evaluations confirmed that YT9 was a stable 2R (2D) substitution and T1BL·1RS translocation line with favorable performance. Resistance phenotyping and microscopic observation of fungal growth revealed that YT9 exhibited resistance to Bgt from the three-leaf stage. Genetic analysis localized the resistance gene to chromosome arm 2RL of rye, designated PmYT9. To map PmYT9, ⁶⁰Coγ-ray irradiation was employed to induce chromosomal structure variants. Integrated GISH, molecular marker analysis, and disease response assessment delimited PmYT9 to a 14.55 Mb interval (831.45-846.00 Mb) on the Lo7 rye reference genome, flanked by markers SW11163 and X2RL78. Additionally, a homozygous T7DS·7DL-2RL translocation line carrying PmYT9 was developed. This study expands the genetic diversity of wheat powdery mildew resistance, provides elite germplasm for wheat resistance breeding, and establishes a foundation for the molecular cloning of PmYT9.