Diseases are the main problem for barley in Latin America. Spot blotch (caused by Cochliobolus sativus), stripe rust (caused by Puccinia striiformis f.sp. hordei) and leaf rust (caused by Puccinia hordei) are three of the most important diseases that attack the crop in the region. Chemical control of those diseases is both economically and environmentally inappropriate, making the development of durable resistant varieties a priority for breeding programs. However, the availability of new resistance sources is a limiting factor. The objective of this work was to map QTL associated to disease resistance in relevant germplasm. In order to identify genomic regions associated with quantitative resistance to these diseases we studied the association between disease severities measured in several environments across the Americas and 1536 SNPs (belonging to the Barley OPA1), using a population of 378 genotypes from ICARDA and national breeding programs. We compared several models for association mapping and used different re-parameterization of the original variables. The best model was trait dependent. We were able to detect candidate QTL for disease resistance for all the traits. Not all of the environments detected significant marker-trait associations. Additionally, not all of the environments that detected significant marker-trait associations identified the same candidate QTL.