Introgression of Wheat Chromosomes into Diploid Rye by Use of a Hexaploid Triticale with an ABRRRR Genome

The objective of this study was to continue attempts to introduce wheat chromosomes, particularly those from the B genome, into diploid rye. An allohexaploid having 2 wheat mixogenomes (1B, 2A, 3B, 4B, 5B, 6A and 7B) and 4 rye genomes (RRRR) was crossed with substitution 2× rye containing the chromosomes of the wheat Agenome except 3A, and next backcrossed with substitution rye. Karyotypes were analysed by C-banding in the produced plants of the generations F 1, BC 1 -F 1, and BC 1 -F 2. In nearly all plants of the F 1 generation (except one), 4–12 wheat chromosomes were found, mainly those of the B genome. A comparison of 2 successive generations indicates that both the mean and range of numbers of wheat chromosomes in the offspring of substitution plants and substitution-addition plants changed sometimes to the advantage of wheat chromosomes but sometimes to their disadvantage. A decline was observed in the contribution of B chromosomes and of chromosomes 2A and 6A, but pollen introduced some wheat chromosomes from the male parent: 1A, 4A, 5A and 7A. Wheat B chromosomes contributed to disturbances in plant development (lack of the spike emergence stage), but usually caused spike sterility, and even the single grains produced were usually unable to germinate. As a result, wheat chromosomes of the B genome were finally completely eliminated from the analysed material. The presence of wheat chromosomes of the A genome in fertile 2× rye plants, as well as their transfer to the next generations, indicate that the A genome is more closely related to the rye genome than the B genome. Positive introgression of wheat chromatin from the A genome into 2× rye depends to a large extent on chromosome engineering by means of appropriate crossing combinations, as A chromosomes from the male parent were much better tolerated than those from the female parent.