Genetic mapping of a leaf rust resistance gene in the former Yugoslavian barley landrace MBR1012

Leaf rust, caused by Puccinia hordei Otth, is an important disease of barley (Hordeum vulgare L.) in many areas of the world. The appearance of new virulent races necessitates the identification of new resistance genes in barley. Screening of spring barley landraces from former Yugoslavia led to the identification of an accession (MBR1012) carrying resistance to the most widespread virulent leaf rust pathotypes in Europe. Ninety-one doubled haploid lines derived from a cross between landrace MBR1012 and the susceptible German cultivar Scarlett were evaluated for resistance to P. hordei isolate I-80 and segregated 48 resistant: 43 susceptible (χ ² _1:1p = 0. 6), indicating a monogenic inheritance of resistance. Using simple sequence repeats (SSR) and single nucleotide polymorphism (SNP) markers, the resistance gene in MBR1012 was mapped to the telomeric region of chromosome 1HS. This gene is assigned the temporary locus designation of Rph _MBR1012 until it can be unequivocally determined to be different from all previously reported resistance genes. The closest flanking markers for Rph _MBR1012 are located 0. 8 cM distal (SNP marker GBS546 and SSR marker GBMS187) and 6. 0 cM proximal (SSR marker GMS21). The diagnostic value of the closest linked markers was assessed in a genetically diverse collection of 51 susceptible and resistant barley lines and cultivars. The SSR GBMS187 predicted the presence of Rph _MBR1012 with 100% accuracy. However, this marker could not be used singly for the rapid incorporation of resistance into high yielding barley cultivars, since it detects a null allele in MBR1012. Therefore, simultaneous use of the markers closely linked to Rph _MBR1012 is needed for transferring Rph _MBR1012 into adapted cultivars.