Wheat is the world"s most widely cultivated cereal. By 2050, global demand for wheat is projected to increase by 60%. In the CWANA region which ICARDA is tasked to serve, wheat is the basic staple and food security crop, contributing over 60% of people"s daily calorific and protein needs. Due to the large proportion of subsistence farmers, wheat production also has a major impact on household food security. Despite this, the productivity of wheat in the region is very low (less than 2.5 t/ha) due largely to the major abiotic (drought, cold, heat, salinity) and biotic (stripe rust, leaf rust, stem rust and Hessian fly) stresses encountered. Most countries in the region are net importers of wheat for human consumption, with regional demand predicted to continue rising. Egypt alone currently imports 9 million tons annually. The situation is further complicated by food production shortfalls associated with climate change which can cause food crises, civil unrest and even migration. The wheat breeding program at ICARDA has developed high yielding and heat tolerant wheat genotypes which have been tested and released as cultivars by many countries in the CWANA region. Out-scaling and intensification of wheat cultivars combined with other improved crop management practices have been carried out by ICARDA in partnership with the national programs in Algeria, Egypt, Iraq, Jordan, Morocco, Sudan, Syria, Tunisia and Yemen resulting with an average increase of wheat production by 28%. The result clearly indicates that development and utilization of climate smart wheat technologies including high yielding and stress tolerant cultivars; integrated crop management systems; establishment of conducive policies and infrastructures are crucial to increase productivity and ensure food and nutrition security.
Septoria tritici blotch (STB) of wheat, caused by the ascomycete Zymoseptoria tritici (formerly Mycosphaerella graminicola), is one of the most important foliar diseases of wheat. In Morocco, STB is a devastating disease in temperate wheat-growing regions, and the yield losses can exceed up to 50% under favorable conditions. The aims of this study were to identify sources of resistance to STB in Septoria Association Mapping Panel (SAMP), which is composed of 377 advanced breeding lines (ABLs) from spring bread wheat breeding program of ICARDA, and to identify loci associated with resistance to STB at seedling (SRT) as well as at the adult plant (APS) stages using genome-wide association mapping (GWAM). Seedling resistance was evaluated under controlled conditions with two virulent isolates of STB (SAT-2 and 71-R3) from Morocco, whereas adult plant resistance was assessed at two hot spot locations in Morocco (Sidi Allal Tazi, Marchouch) under artificial inoculation with a mixture of STB isolates. At seedling stage, 45 and 32 ABLs were found to be resistant to 71-R3 and SAT-2 isolates of STB, respectively. At adult plant stage, 50 ABLs were found to be resistant at hot spot locations in Morocco. Furthermore, 10 genotypes showed resistance in both locations during two cropping seasons. GWAM was conducted with 9,988 SNP markers using phenotypic data for seedling and the adult plant stage. MLM model was employed in TASSEL 5 (v 5.2.53) using principal component analysis and Kinship Matrix as covariates. The GWAM analysis indicated 14 quantitative trait loci (QTL) at the seedling stage (8 for isolate SAT-2 and 6 for isolate 71-R3), while 23 QTL were detected at the adult plant stage resistance (4 at MCH-17, 16 at SAT-17, and 3 at SAT-18). SRT QTL explained together 33.3% of the phenotypic variance for seedling resistance to STB isolate SAT-2 and 28.3% for 71-R3, respectively. QTL for adult plant stage resistance explained together 13.1, 68.6, and 11.9% of the phenotypic variance for MCH-17, SAT-17, and SAT-18, respectively. Identification of STB-resistant spring bread wheat germplasm in combination with QTL detected both at SRT and APS stage will serve as an important resource in STB resistance breeding efforts.
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