Characterization of rust-resistant wheat-Agropyron intermedium derivatives by C-banding, in situ hybridization and isozyme analysis.

Chromosome constitutions of three wheat-Agropyron intermedium derivatives were identified by C-banding analysis, in situ hybridization using biotin-labeled genomic Ag. intermedium DNA as a probe and isozyme analysis. Lines W44 and W52 were identified as 7Ai-2(7D) and 7Ai-2(7A) chromosome substitution lines carrying the same chromosome pair of Ag. intermedium. The alien chromosome was found to be homoeologous to group 7 based on C-banding, meiotic pairing and isozyme analyses. Line W49 was identified as a wheat Ag. intermedium chromosome translocation line. The breakpoint of the T2AS · 2AL-7Ai-2L translocation is located in the long arm at a fraction length of 0.62, and the transferred Ag. intermedium segment has a size of about 2.4 μm. Lines W44 and W52 expressed Ag. intermedium genes for resistance to leaf rust, stripe rust and stem rust, but only leaf rust resistance was expressed in W49. The results show that the leaf rust resistance gene(s), designated Lr38, is located in the distal half of the long arm of chromosome 7Ai-2, whereas the genes for resistance to stem rust and stripe rust are located either in the short arm or in the proximal region of the long arm of this chromosome.