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Resistance traits are economically important in crops in terms of accessibility to promising resistant germplasm. This study was conducted to evaluate SNP marker-trait association for Cereal Cyst Nematode (CCN), Heterodera filipjevi, in a large number of natural bread wheat populations. Phenotypic data analyzed using GLM (Generalized Linear Model) indicated significant differences among the landrace accessions for resistance to H. filipjevi. The genotyping was performed by 152K SNP chip on 188 accessions. After filtering, 10,471 polymorphic SNPs were employed for Genome Wide Association Study (GWAS). Population structure among the wheat genotypes were investigated using 840 well distinct SNP markers. Two sub-populations were revealed by structure software, and eleven markers were found to be significantly (P-value< 0.001) associated with resistance to H. filipjevi on chromosomes 2A, 3B, 4A, 4B, 5A, 5B, 5D, and 6B. The linkage disequilibrium analysis for all significantly associated SNPs showed that markers on chromosomes 4A and 4B were in high intra-chromosomal linkage disequilibrium, and, consequently, eight markers were recommended as strongly associated with resistance to H. filipjevi. The present study demonstrated valuable sources of resistance in the studied wheat genotypes against a widespread and important species of CCNs. The associated markers could be used in molecular breeding programs of bread wheat. [ABSTRACT FROM AUTHOR]

The new stem rust race Ug99 is an alarming threat to the wheat (Triticum aestivum L.) production of the world for the very fact that it overcomes many of the known Sr genes including the most commonly used genes such as 5r31, Sr24, and Sr36. The wheat breeding program at the International Center for Agricultural Research in the Dry Areas (ICARDA) has distributed the first stem rust resistant spring wheat yield trials composed of 24 wheat genotypes for the Central and West Asia and North Africa (CWANA) region to identify high yielding wheat genotypes, which can be recommended for direct release and/or parentage purposes by the National Agricultural Research Systems (NARS5). The additive main effects and multiplicative interaction (AMMI) analysis of variance for grain yield (kg ha-1) of 24 wheat genotypes tested in 15 environments showed that wheat grain yield was significantly (p <0.01) affected by environments (E), genotypes (G), and genotype x environment interaction (GEl). From the total sum of squares due to treatments (G + E + GEl), E contributed 90.1% and GEl accounted for 8.3% while G effect represented only 1.6%. According to AMMI2 estimate, Baasha-14 and Amir-2 with mean grain yield levels of 5168 and 5127 kg ha-1, respectively, are identified as the best genotypes with high yield potential across a wide range of environments. Based on correlation and clustering analysis among environments, the Ghab site in Syria (E7) is identified as the highest yielding and best correlated site and therefore it is recommended as a key location for evaluation of wheat germplasm yield potential in ICARDA's wheat breeding program. We recommend the high yielding and Ug99 resistant genotypes identified in this study for direct release as replacement of the susceptible varieties by the respective NARS and/or to be used as parents at ICARDA and by NARS collaborators. [ABSTRACT FROM AUTHOR]