Transfer of stem rust resistance gene SrB from Thinopyrum ponticum into wheat and development of a closely linked PCR-based marker
We report transfer of a rust resistance gene named SrB, on the 6Ae#3 chromosome, to wheat by recombination with the 6Ae#1 segment carrying Sr26 and development of a linked marker.
A stem rust resistance gene from a South African wheat W3757, temporarily named SrB, has been transferred onto chromosome 6A. Line W3757 is a 6Ae#3 (6D) substitution line in which the Thinopyrum ponticum chromosomes carry SrB. Crosses were made between W3757 and a T6AS·6AL-6Ae#1 recombinant line named WA-5 carrying the stem rust resistance gene Sr26 on a chromosome segment from another accession of Th. ponticum. The 6Ae#1 and 6Ae#3 chromosomes had previously been shown to pair at meiosis and were polymorphic for the distally located RFLP probes BCD001 and MWG798. A recombinant plant (Type A) was identified carrying a distal chromosome segment from the 6Ae#3 chromosome and a sub-terminal segment from the 6Ae#1 chromosome. Rust tests on the recombinant Type A showed the infection type for SrB. Segregation and linkage data combined with genomic in situ hybridization studies demonstrated that SrB had been transferred to wheat chromosome arm 6AL by recombination between the Thinopyrum chromosome segments. A recombinant positive for the 6Ae#1–6Ae#3 chromosome showed enhanced stem rust resistance compared to the 6Ae#3 addition line in repeated rust tests. A diagnostic PCR-based marker was developed for the 6Ae#3 chromosome segment on the Type A recombinant carrying SrB that distinguishes it from the Sr26-containing segment. A stem rust resistant line which combines SrB with Sr26 would be a great addition to the pool of resistant germplasm for wheat breeders to achieve more durable and effective control of stem rust because virulence has not been found for either of these two genes.
This research was supported by the Grains Research and Development Corporation, Australia. We thank Dr. Kenneth Shepherd (The University of Adelaide, retired) for suggesting the project. The laboratory technical assistance of Ms. Dawn Verlin and Dr. Julia Humphries of The University of Adelaide is gratefully acknowledged.
Author contribution statement
ID made the initial crosses and identified the new 6Ae#1-6Ae#3 recombinant using a unique RFLP probe developed by AG. PZ and SH verified the presence of the SrB gene and linked the PCR marker to SrB resistance. PZ performed GISH analysis. RM and XX developed the PCR-based marker specific for the 6Ae#3 segment, while JZ and EL contributed to analyzing and interpreting data (some unpublished) which pointed to the likely inclusion of Sr26 as an additional gene in the recombinant. RM, PZ and ID wrote the manuscript. All authors reviewed the manuscript.
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Conflict of interest
The authors state that they have no conflict of interest.
The authors state that all research activities comply with ethical standards of their respective institutions and funding organizations.
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