Chromosomal locations of genes for stem rust resistance in monogenic lines derived from tetraploid wheat accession ST464

The genetics of resistance to stem rust (caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. and Henn.) in durum (Triticum turgidum L. ssp. durum) is not as well understood as for bread wheat (T. aestivum L). Our objective was to determine the chromosomal location of genes for stem rust resistance in four monogenic lines derived from the Ethiopian tetraploid landrace ST464. The four monogenic lines were crossed to a set of stem rust susceptible aneuploids based on the tetraploid line 47-1. We observed chromosome pairing in the hybrids and made testcrosses to 'Rusty' durum. Monogenic lines ST464-A1 and ST464-A2 were observed to carry a 2A/4B translocation, and subsequent crosses proved that the translocation was derived from ST464. Testcross F. seedlings were inoculated with one of three stem rust pathotypes and classified for segregation for resistance to identify the critical chromosome for each monogenic line. The stem rust resistance genes in monogenic lines ST464-A1, ST464-A2, and ST464-C1 were located to chromosomes 6A, 2B, and 6A, respectively. The gene in ST464-B1 may be located to chromosome 4A, because it appeared it was not located on any of the other 13 chromosomes. The four ST464 monogenic lines and hexaploid lines carrying Sr9e and Sr13 were then tested with eight stem rust pathotypes with the objective of postulating the genes present in the monogenic lines. The genes in ST464-A2 and ST464-C1 were postulated to be Sr9e and Sr13, respectively.