LINKAGE BETWEEN LEAF RUST RESISTANCE GENES AND MORPHOLOGICAL MARKERS IN BARLEY

Studies were undertaken to map the chromosome location of leaf rust resistance genes Rph3, Rph7, and Rph12 in the barley cultivars Estate, Cebada Capa, and Triumph using various morphological markers. Crosses were made between genotypes resistant to Puccinia hordei and leaf rust susceptible morphological marker stocks. F2 plants were evaluated for reaction (infection type) to P. hordei, and presence of morphological markeT characters. Segregation data indicated the position of the Rph3 allele in Estate barley on the long arm of chromosome 1. A linkage distance of 9.7 +/- 4.2% was found between the Rph3 and X(a) loci. The independence of segregation of Rph3 with n and lk2 suggests that the Rph3 locus is more distal than the X(a) locus on the long arm of chromosome 1. Linkage between Rph7 in Cebada Capa and markers on chromosomes 1 to 7 was not observed- A single resistance gene was identified in Triumph and was designated Rph12. The Rph12 locus was linked with the r and s loci on chromosome 7, with recombination values of 26.1 +/- 2.3% and 39.5 +/- 2.9%, respectively.