Durum wheat (Triticum turgidum L. cv. durum) is the raw material by excellence for the manufacture of dry pasta, due to the hardness and vitreosity of its grain. In Argentina, the growing area of the crop is 129,255 ha (2020/21), distributed among the southeast of Buenos Aires province and the central and north-west regions of the country. Crop yield is frequently reduced due to the occurrence of biotic stresses such as rusts. Among them, the stripe rust or yellow rust (YR) caused by the fungus Puccinia striiformis f.sp. tritici (Pst) has caused yield losses of 5 to 25%. The occurrence of new highly virulent races has made it a severe disease for durum wheat. One of the most effective strategies to prevent these losses is the development of resistant cultivars with high yield potential. In this study, a diverse collection of 197 cultivars and advanced breeding lines was evaluated for resistance to YR at field conditions, under natural and controlled infection in four environments (Argentina and Mexico). In addition, the response to seedling stage infection was evaluated using locally collected races. To study the linkage disequilibrium (LD), population structure and association mapping a matrix of 4,854 neutral SNPs and 9 SNPs located in genes were used. The critical LD decay value was 11.8 Mb along the genome. Five subpopulations were identified using a discriminant analysis of principal components (DAPC). Eleven genotypes showed high levels of resistance in at least 3 environments and only 3 in the total of the environments. Fifteen SNPs distributed in chromosomes 1A, 1B, 2A, 2B, 3A, 5B, 6A and 7B associated with resistance in adult plants were identified in at least 3 environments, using a mixed linear model (MLM). Two out of these SNPs, located on chromosomes 2B and 7B were mapped in all four environments. Nine SNP markers located on chromosomes 1A, 2A, 4B and 7B were associated with race-specific resistance at seedling stage and under field conditions. Four out of the five SNPs associated to YR in 1B were located within an interval of 2.18 Mb. The SNPs associated on the distal region of 7BL chromosome were close to a gene cluster encoding resistance RPM1 and NBS-LRR proteins. These results contribute to the better understanding of the genetic basis of resistance to YR, providing potential markers for genetic improvement through their use in marker assisted selection.
