Abstract:

Wheat (Triticum aestivum L.) leaf rust, caused by Puccinia triticina (formerly P. recondita f. sp. tritici), is one of the most destructive diseases on wheat production throughout the world. The exploitation of markers and locations of leaf rust resistance (Lr series) genes will facilitate marker-assisted selection, and benefit the breeding of effective leaf rust resistant cultivars and the gene cloning. Lr45 is a resistant gene against wheat leaf rust disease originated from Secale cereale and is located on the chromosome 2A. No virulent isolate to the gene has been found to date. SSR are abundant, highly polymorphic, evenly distributed over the genome, and required only small amounts of genomic DNA for analysis. Therefore, it is highly suitable for genetic markers in wheat for mapping agronomically important genes. And it provides a robust tool for verification and localization of wheat target genes. In this study, SSR markers were employed to tag the gene Lr45 and four NILs (TcLr11, TcLr17, TcLr37, and TcLr45), the original parent Secale cereale, the susceptible line Thatcher and 157 individuals of F₂ progeny derived from a cross between TcLr45 and Thatcher were used to marker gene Lr45. The wheat seedlings of parents and F₂ generation were inoculated solely with leaf rust spora, and cultured in greenhouse. At the 14th days after inoculation, infection type of all plant materials were scored in six grades with Roelfs’s system. Genomic DNA of wheat was extracted by CTAB. Fifty-nine SSR and EST-SSR primer pairs located on wheat chromosome 2A were screened, and the PCR-amplified products were either checked on 3% agrose gel or on a denaturing 6.0% poly-acrylamide gel. Eleven primer pairs displayed polymorphism of TcLr45 and four SSR markers (Xgwm95, Xgwm47, Xgwm372, and Xgwm122) co-segregated with Lr45 were acquired. Xgwm95 gave difference bands in F₂ populations, and Xgwm47 have a resistance band of 133 bp. Resistance and susceptibility sequenced marker Xgwm95, resistance sequenced Xgwm47 showed that they include repeats of di-nucleotide. Xgwm372 and Xgwm122 gave a specific resistance band of 180 bp and 110 bp respectively, also in Secale cereale, the original parent of Lr45. They can be used in MAS directly. No EST-SSR marker for Lr45 was acquired in this study.

Key words: SSR, Wheat leaf rust, Resistance Gene, Lr45