Pathogens are a reason for low yield in common wheat (Triticum aestivum L.). Stripe rust (or yellow rust), caused by the fungus Puccinia striiformis f. sp. tritici (Pst), is one of the most important foliar diseases of wheat. One of the most cost-effective and environmentally sound ways to control stripe rust is to use plant varieties that are resistant to this pathogen. It is an important task for wheat breeders and pathologists to identify new genes and pyramid them in order to achieve high-level, durable resistance to stripe rust. One spring wheat germplasm, HRMSN-81, with resistance to the most dominant races in China, is identified from the CIMMYT breeding lines. To elucidate the genetic basis of its resistance, HRMSN-81 was crossed with susceptible wheat genotype Taichung 29. Seedlings of the parents were tested with Chinese Pst isolates CYR31, CYR32, and CYR33 under controlled greenhouse conditions, and adult plants of the parents and F1, F2, and F2:3 progeny were inoculated with the epidemic stripe rust mixed races, including CYR31, CYR32, and CYR33, in fields under natural infection.
Genetic analysis showed that HRMSN-81 has a single dominant gene conferring all-stage resistance, temporarily designated as YrHRMSN-81. Resistance gene analogue polymorphism (RGAP), simple sequence repeat (SSR), target region amplified polymorphism (TRAP), and sequence-related amplified polymorphism (SRAP) techniques in combination with bulked segregant analysis (BSA) were used to identify molecular markers linked to the resistance gene. A linkage map consisting of six RGAP, two SSR, one TRAP, and two SRAP markers was constructed for YrHRMSN-81 using 148 F2 plants. The gene was mapped to chromosome arm 2DS by testing the complete set of nulli-tetrasomic lines and selected ditelosomic lines with two RGAP markers and was further confirmed by two chromosome-specific SSR markers. The results of gene characteristics and chromosome locations indicated that YrHRMSN-81 was probably a new stripe rust resistance gene. The two flanking markers Xwgp-180bp (93% polymorphism rate) and Xwmc453 (91% polymorphism rate) detected 100% polymorphism of the 56 tested wheat genotypes when they were used in combination. The identification of the gene YrHRMSN-81 and the determination of the flanking markers should be useful for rapidly transferring it in wheat breeding programs.
Genome-Wide Association Mapping of Loci for Resistance to Stripe Rust in North American Elite Spring Wheat Germplasm
