EXOTIC BARLEY GERMPLASMS IN BREEDING FOR RESISTANCE TO SOIL-BORNE VIRUSES

Soil-borne mosaic inducing viruses, i.e., barley mild mosaic virus (Ba MMV), barley yellow mosaic virus (BaYMV), and BaYMV-2, cause one of th e most important diseases of winter barley in Western Europe. Since re sistance of all commercial European barley cultivars is due to a singl e recessive gene (ym4) which is not effective against BaYMV-2, exotic barley germplasms (Hordeum vulgare L., H. spontaneum Koch) were screen ed for resistance to the different viruses and analyzed for genetic di versity concerning BaMMV resistance. In these studies it turned out th at resistance to BaMMV is entirely inherited recessively and that a hi gh degree of genetic diversity concerning resistance is present within the barley gene pool at least to BaMMV. Therefore, exotic barley germ plasms are a very useful source for the incorporation of different res istance genes into barley breeding lines, thereby enabling the breeder to create cultivars adapted to cultivation in the growing area of fie lds infested by soil-borne viruses. Furthermore, in order to obtain mo re information on these germplasms they were evaluated for agronomic t raits and isozyme, RFLP and RAPD analyses were carried out on these va rieties to detect markers linked to the respective resistance genes an d to obtain information on the genetic similarity between yellow mosai c resistant barley accessions derived from different parts of the worl d. Actual results of these studies are briefly reviewed.