Introduction of new 1RS into translocation wheats

Research project P 13852 Introdution of new 1RS into translocation wheats Tamas LELLEY 11.10.1999 Wheat varieties with a 1BL.1RS translocation are grown world wide. It is generally believed, that the translocated rye chromatin (IRS) provides disease resistance to the host wheat variety, improves its yield potential and adaptation. At the same time, however, it reduces breadmaking quality. The source of IRS for most of the existing translocation varieties is the same German rye population "Petkus". It was introduced into wheat unconsciously in the 40s. Wheat breeding could profit greatly if the genetic variation available in rye could be used to enlarge the genetic base of future wheat varieties having IRS translocation. Unfortunately, the effect of a specific IRS on the phenotype of wheat can only be assessed after its transfer into wheat is succeeded, and proper comparisons with corresponding wheat lines without the translocation can be made. In the proposed experiment, transfer of new IRS from rye into wheat will be carried out in two ways (1) by homologous recombination using existing translocation varieties and (2) by translocations in wheat varieties monosomic for the homoeologous group one chromosomes. The main objectives of the work are: (1) creating genetic variation in IRS to overcome the limitations of the available variation in the present day translocation varieties; (2) to tap the vast genetic variation available in the gene pool of Secale cereale; (3) compare the two production methods with respect to their efficiency in producing new variation and new translocations respectively, and (4) preliminary testing the influence of the induced new variation on the phenotype of the recipient wheat genotype for its usefulness for wheat breeding.

Numerous wheat varieties world wide carry in their genome the half of a rye chromosome with the short designation 1RS. The originally complete rye chromosome was introduced into wheat unconsciously in the 40es of the last century. The prove of a spontaneous 1B/1R chromosome substitution (the complete 1B chromosome of wheat was replaced by 1R from rye) was presented only in the 70es. Soon, it was found that, along with the complete chromosome substitution, a translocation version of the two chromosome arose, composed of the long arm of 1B and the short arm of 1R, known today as the 1BL.1RS translocation. The benefit of this translocation for wheat was quickly realized, though, this benefit will often be controversially discussed. But a sign of a favorable effect of 1RS on wheat, can be recognized by the fact, that world wide several hundred wheat varieties have been and still are being released with 1RS bread deliberately but often enough without knowing about the presence of the translocation. A problem is caused by the fact, that its spontaneous introduction into wheat was a single event and therefore, due to lack of allelic variation, no genetic progress is possible for characters controlled by 1RS. The first target of our project was to change this situation and we indeed succeeded to introduce new allelic variation into conventional 1RS. As a next step we wanted to find out about the size of the chromosome part which we were able to exchange through recombination. For this purpose molecular markers are being used because their relative position along the chromosome are usually known. This part of the work turned out to be less successful, because the available marker covered only a small part of 1RS and therefore only exchange in this chromosome region was possible. We have decide to use a new type of marker, which we have had to develop by our self, which, however, was supposed to cover evenly the entire 1RS chromosome arm. We have succeeded to establish 30 such markers, with which it is now possible along the whole chromosome arm to detect a recombination. With this project we have proven, that new genetic variation can be introduced with relatively simple means into 1RS. For such introduction the whole gene reservoir of cultivated but also wild rye can be used. We have proven, that with the newly developed markers exchange can be detected along the total 1RS and this markers are also suitable for further studies concerning the genetic structure of this cereal chromosome, which can be considered as a model in a polyploid plant like wheat.