Yellow rust, caused by Puccinia striiformis f. sp. tritici, is a common and serious fungal disease of wheat (Triticum aestivum L.) all over the world and particularly in the Central and West Asia and North Africa region. A cultivars’ resistance can break down quickly when new virulent pathotypes evolve in the ongoing arms race between host plant and pathogen. We investigated the disease development of 196 bread wheat genotypes under field conditions for two years 2014-2015 at ICARDA station, Marchouch, Morocco. The severity and the response rating were scored for adult plant field reaction following modified Cobb’s scale. The Warrior (PstS7) race was prevalent in 2013 in Morocco while the virulence in the next two years was unknown. However, in 2016, a sampling was done systematically, and a new distinct race (PstS14) was detected along with PstS10 known as Warrior (-) previously reported in Algeria and Spain in 2014 and perhaps in Morocco as well but no data is available to confirm. Given that the breakdown of the resistance to stripe rust in a widely grown cultivar “Arrihane” in Morocco, which used to have moderate resistance to stripe rust in the past few years, became highly susceptible and scored 70-90S, and the resistance rating that dropped from 147 resistant genotypes in 2014 to 96 in 2015 might indicate that PstS10 and PstS14 (or may be other unknown races) possibly contributed to variation in the reaction type and the resistance in 2015. GWAS using mixed linear model identified 23 markers on chromosomes 2A, 2B, 2D and 7B significantly associated with adult plant resistance at false discovery rate (FDR-adjusted ≤ 0.05). BLAST analysis confirmed that YrR61 and Yr17 were mostly the candidate genes linked to the marker Tdurum_contig29983_490 on chromosome 2A and the marker Ku_c7740_879 overlapped with the QTL QYr.cim-2BS _Francolin designed as YrF previously reported on chromosome 2B.
