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United States Department of Agriculture

Agricultural Research Service

Research Project: SUNFLOWER GERMPLASM DIVERSIFICATION AND CHARACTERIZATION UTILIZING WILD SUNFLOWER SPECIES, CYTOGENETICS, AND APPLIED GENOMICS

Location: Sunflower Research

Title: A novel Robertsonian translocation event leads to transfer of a stem rust resistance gene (Sr52) effective against race Ug99 from Dasypyrum villosum into bread wheat

Authors
item QI, LILI
item Pumphrey, M -
item Friebe, Bernd -
item Zhang, Peng -
item Qian, Chen -
item BOWDEN, ROBERT
item ROUSE, MATTHEW
item JIN, YUE
item Gill, Bikram -

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2011
Publication Date: March 25, 2011
Repository URL: http://naldc.nal.usda.gov/catalog/49605
Citation: Qi, L.L., Pumphrey, M.O., Friebe, B., Zhang, P., Qian, C., Bowden, R.L., Rouse, M.N., Jin, Y., Gill, B.S. 2011. A novel Robertsonian translocation event leads to transfer of a stem rust resistance gene (Sr52) effective against race Ug99 from Dasypyrum villosum into bread wheat. Theoretical and Applied Genetics. 123:159-167.

Interpretive Summary: Wheat stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn.) has successfully been controlled in most wheat production areas of the world by the use of genetic resistance in wheat cultivars for several decades. However, a new emerging race of stem rust, called Ug99 identified in Uganda in 1999 and its derivatives have defeated several important stem rust resistance genes widely used in wheat (Triticum aestivum L.) production, rendering much of the worldwide wheat acreage susceptible. Alarmingly, race Ug99 is virulent on most known major genes of wheat origin. Therefore, it is urgent to develop diverse germplasm that has effective resistance to this dangerous new race. Dasypyrum villosum (L.) Candargy Schur. is a diploid wild relative of bread wheat native to the Mediterranean region. The screening a large collection of wheat relatives and genetic stocks for resistance to Ug99 revealed that most accessions of the D. villosum were highly resistant. The further screening of a set of wheat-D. villosum chromosome addition lines, wheat stocks containing 21 pairs of wheat chromosomes and one pair of D. villosum chromosomes, to stem rust race Ug99 revealed that the wheat-D. villosum disomic addition line DA6V#3 was moderately resistant to race Ug99. The objective of the present study was to introduce stem rust resistance gene from D. villosum into wheat through producing compensating wheat-D. villosum whole arm translocations involving exchanges of chromosome arm 6V#3S to the wheat chromosome arm 6DL and 6V#3L to the wheat chromosome arm 6DS. Seven 6V#3-specific molecular markers were developed for screening F2 progeny derived from plants double-monosomic for chromosomes 6D and 6V#3 (20 pairs of wheat chromosomes plus one 6D chromosome and one 6V#3 chromosome). Surprisingly, although 6D was the target chromosome, all recovered whole arm translocations involved chromosome 6A. Homozygous translocations (T6AS.6V#3L and T6AL.6V#3S) with good plant vigor and full fertility were selected from F3 families. A stem rust resistance gene was mapped to the long arm 6V#3L in T6AS.6V#3L and was designated as Sr52. Sr52 is temperature-sensitive and is most effective at 16 C, partially effective at 24 C, and ineffective at 28 C. The T6AS.6V#3L stock is a new source of resistance to Ug99, is cytogenetically stable, and may be useful in wheat improvement.

Technical Abstract: Stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn.) (the causal agent of wheat stem rust) race Ug99 (also designated TTKSK) and its derivatives have defeated several important stem rust resistance genes widely used in wheat (Triticum aestivum L.) production, rendering much of the worldwide wheat acreage susceptible. In order to identify new resistance sources, a large collection of wheat relatives and genetic stocks maintained at the Wheat Genetic and Genomic Resources Center was screened. The results revealed that most accessions of the diploid relative Dasypyrum villosum (L.) Candargy were highly resistant. The screening of a set of wheat-D. villosum chromosome addition lines revealed that the wheat-D. villosum disomic addition line DA6V#3 was moderately resistant to race Ug99. The objective of the present study was to produce and characterize compensating wheat-D. villosum whole arm Robertsonian translocations (RobT) involving chromosomes 6D of wheat and 6V#3 of D. villosum through the mechanism of centric breakage-fusion. Seven 6V#3-specific EST-STS markers were developed for screening F2 progeny derived from plants double-monosomic for chromosomes 6D and 6V#3. Surprisingly, although 6D was the target chromosome, all recovered RobTs involved chromosome 6A implying a novel mechanism for the origin of RobTs. Homozygous translocations (T6AS.6V#3L and T6AL.6V#3S) with good plant vigor and full fertility were selected from F3 families. A stem rust resistance gene was mapped to the long arm 6V#3L in T6AS.6V#3L and was designated as Sr52. Sr52 is temperature-sensitive and is most effective at 16 C, partially effective at 24 C, and ineffective at 28 C. The T6AS.6V#3L stock is a new source of 1 resistance to Ug99, is cytogenetically stable, and may be useful in wheat improvement.

Last Modified: 9/29/2014
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