S Kicherer1, U Walther1 and A Graner2

1Federal Centre for Breeding Research on Cultivated Plants, Institute for Epidemiology and Resistance, Theodor-Roemer-Weg 4, 06449 Aschersleben, Germany; 2Institute of Plant Genetics and Crop Plant Research, Corrensstraße 3, 06466 Gatersleben, Germany

Background and objectives
Resistance of barley against leaf rust (Puccinia hordei) based on single major genes has been overcome to a great extent by new races of the pathogen, because the genes are widely used in barley breeding programmes. In addition to these Rph genes deriving from Hordeum vulgare, there is increasing interest in genes from wild barley species such as Hordeum spontaneum [1]. The creation of dense molecular maps of the barley genome provides a tool for effective searching for new resistance genes (fe2).

Materials and methods
F2 progenies deriving from crosses of highly resistant H. spontaneum lines with a susceptible barley cultivar have been investigated for leaf rust attack during the seedling stage and for segregation. Ten F2 populations, most segregating according to a single resistance gene, were subjected to bulked segregant analysis in order to identify RFLP markers for leaf rust resistance deriving from H. spontaneum. Two F2 progenies consisting of double haploid lines have been used for mapping new resistance genes.

Results and conclusions
Six F2 populations were found to possess marker loci causing polymorphism between DNA bulks derived from susceptible and resistant plants, respectively. The locus on the short arm of chromosome 2H appears to be associated with leaf rust resistance of three populations. A marker locus on chromosome 5H was determined in the progeny of three H. spontaneum lines differrent from those mentioned above. A single resistance gene was mapped on the short arm of chromosome 2H using doubled-haploid populations deriving from two other H. spontaneum lines. The results show that the resistance of several lines is connected with the same chromosome region. Populations suitable to tests for allelism are available. Chromosome 2H is known to carry the major gene, Rph1, not coding resistance against the leaf rust isolates used for inoculation. The same phenomenon is found on chromosome 5H, carrying Rph11 deriving from barley cv. Trumpf, so that there are at least two new genes for leaf rust resistance deriving from H. spontaneum.

1. Moseman JG, Nevo E, El-Morishdy MA, 1990. Reactions of Hordeum spontaneum to infection with two cultures of Puccinia hordei from Israel and United States. Euphytica 49, 169-175.
2. Graner A, Jahoor A, Schondelmaier J et al., 1991. Construction of an RFLP map in barley. Theoretical and Applied Genetics 83, 250-256.