Simultaneous Transfer of Leaf Rust and Powdery Mildew Resistance Genes from Hexaploid Triticale Cultivar Sorento into Bread Wheat

Abstract

Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici, and wheat leaf rust, caused by Puccinia triticina Eriks, are two important diseases that severely threaten wheat production. Sorento, a hexaploid triticale cultivar from Poland, shows high resistance to the wheat powdery mildew isolate E09 and the leaf rust isolate PHT in Beijing, China. To introduce resistance genes into common wheat, Sorento was crossed with wheat line Xuezao, which is susceptible to both diseases, and the F₁ hybrids were then backcrossed with Xuezao as the recurrent male parent. By marker analysis, we demonstrate that the long arm of the 2R (2RL) chromosome confers resistance to both the leaf rust and powdery mildew isolates at adult-plant and seedling stages, while the long arm of 4R (4RL) confers resistance only to powdery mildew at both stages. The chromosomal composition of BC₂F₃ plants containing 2R or 2RL and 4R or 4RL in the form of substitution and translocation were confirmed by GISH (genomic in situ hybridization) and FISH (fluorescence in situ hybridization). Monosomic and disomic substitutions of a wheat chromosome with chromosome 2R or 4R, as well as one 4RS-4DL/4DS-4RL reciprocal translocation homozigote and one 2RL-1DL translocation hemizigote, were recovered. Such germplasms are of great value in wheat improvement.

Keywords: FISH; GISH; hexaploid triticale; leaf rust; marker analysis; powdery mildew; resistance.

Figure 1

Procedure for transferring resistance from Sorento into Xuezao.

Figure 2

Marker analysis of BC₂F₂ plants segregating for 4R using rye-specific markers (GRM0022, MAG1424, and GRM1178) on the long arm of 4R chromosome and markers ((TAG)7, REMS1160, and GRM0215) on the short arm of 4R chromosome. Ten plants (lane 3–12) resistant to powdery mildew at the seedling stage and 10 susceptible plants (lane 13–22) were analyzed. Lane 3–7 and 18–22 show plants with entire 4R and without 4R chromosome, respectively. Lane 8–12 and 13–17 signify the presence of 4RL and 4RS alone, respectively. Lane 1 and lane 2 signify the resistant parent (Sorento) and susceptible parent (Xuezao), respectively.

Figure 3

Marker analysis of BC₂F₂ plants segregating for 2R using rye-specific markers (CGG9, SCM149, and REMS1251) on the long arm of 2R chromosome and markers (CGG62, SCM153, and REMS1203) on the short arm of 2R chromosome. Ten plants (lane 3–12) resistant to powdery mildew at the seedling stage and 10 susceptible plants (lane 13–22) were analyzed. Lane 3–7 and 18–22 show plants with entire 2R and without 2R chromosome, respectively. Lane 8–12 and 13–17 signify the presence of 2RL and 2RS alone, respectively. Lane 1 and lane 2 signify the resistant parent (Sorento) and susceptible parent (Xuezao), respectively.

Figure 4

Chromosome composition of BC₂F₃ line 1289 by FISH (B) and GISH (A) using probe pAs1 (red) and probe pSc119.2 (green). A pair of 2R chromosomes from Sorento have been introduced into wheat.

Figure 5

Chromosome composition of BC₂F₃ line 1419 by FISH (B) and GISH (A) using probe pAs1 (red) and probe pSc119.2 (green). Line 1,419 contains a pair of 4R chromosomes from Sorento.

Figure 6

Chromosome composition of BC₂F₃ line 1204 by FISH (B) and GISH (A) using probe pAs1 (red) and probe pSc119.2 (green). Line 1,204 shows to be a 4R-4D reciprocal translocation in which the short arm of 4R chromosome was translocated to the long arm of 4D chromosome and the long arm of 4R chromosome was translocated to the short arm of 4D chromosome.

Figure 7

Chromosome composition of BC₂F₃ line 1,887 by FISH (B) and GISH (A) using probe pAs1 (red) and probe pSc119.2 (green). Line 1,887 was shown to be a monosomic 2RL-1DL translocation line in which the long arm of 2R was translocated to the long arm of 1D chromosome.