Background Global wheat productivity is seriously challenged by a range of rust pathogens, especially leaf rust derived from Puccinia triticina. Since the most efficient approach to control leaf rust is genetic resistance, many efforts have been made to uncover resistance genes; however, it demands an ongoing exploration for effective resistance sources because of the advent of novel virulent races. Thus, the current study was focused on detecting leaf rust resistance-related genomic loci against the P. triticina prevalent races by GWAS in a set of Iranian cultivars and landraces. Results Evaluation of 320 Iranian bread wheat cultivars and landraces against four prevalent rust pathotypes of P. triticina (LR-99–2, LR-98–12, LR-98–22, and LR-97–12) indicated the diversity in wheat accessions responses to P. triticina. From GWAS results, 80 leaf rust resistance QTLs were located in the surrounding known QTLs/genes on almost chromosomes, except for 1D, 3D, 4D, and 7D. Of these, six MTAs (rs20781/rs20782 associated with resistance to LR-97–12; rs49543/rs52026 for LR-98–22; rs44885/rs44886 for LR-98–22/LR-98–1/LR-99–2) were found on genomic regions where no resistance genes previously reported, suggesting new loci conferring resistance to leaf rust. The GBLUP genomic prediction model appeared better than RR-BLUP and BRR, reflecting that GBLUP is a potent model for genomic selection in wheat accessions. Conclusions Overall, the newly identified MTAs as well as the highly resistant accessions in the recent work provide an opportunity towards improving leaf rust resistance.

Lr 34 is a vital gene in developing resistance to leaf rust, stripe rust, and powdery mildew of wheat. Providing simultaneous resistance to various pathogens has made this gene valuable in breeding for wheat resistance to many diseases. The present study investigates the csLV34 marker's capability in diagnosing this locus in130 wheat commercial cultivars and advanced wheat lines from Iran, and assesses the impact of this gene on disease severity in field conditions. To assess the reactions of cultivars and lines which contained Lr 34 under epidemic conditions of leaf rust, these cultivars were cultivated during the 2009 and 2010 cropping season. Of the 130 studied cultivars, 43 contained Lr 34 . Cultivars that were selected and studied in stress conditions had the most frequent presence of Lr 34 . It can be concluded that this gene plays a vital role in increasing the tolerance of cultivars under stress conditions. Lr 34 seems to cause active transition of materials out of the cell. In addition to being resistant to several important diseases of wheat, Lr 34 can increase tolerance to stresses such as salinity. Considering the calculated value for AUDPC (3% -440%/d) in cultivars containing Lr 34 , it seems that some cultivars contained additional resistance genes. The rate of infection in all cultivars, when presence of Lr 34 was detected through the molecular marker, was lower than in other cultivars. Field results confirmed the results of the analysis using the csLV34b molecular marker.

Leaf or brown rust caused by Puccinia triticina Eriks. (Pt) is a major biotic constraint threatening bread wheat production worldwide. The continued evolution of new races of Pt necessitates a constant search for the identification of new resistance genes, or QTLs, to enhance the resistance durability of bread varieties. On a panel of 320 bread wheat accessions, we used a genome-wide association study (GWAS) technique to map loci associated with Pt resistance using single-nucleotide polymorphism markers (SNPs) generated by genotyping-by-sequencing (GBS). The panel was tested with five Pt races gathered from different regions of IRAN to identify loci associated with seedling resistance. After estimating genetic relatedness and population structure among accessions, GWAS discovered a total of 19 SNPs on chromosomes 1B, 2B, 3A, 3B, 4A, 5B, 5D, 6A, 6B, 6D, 7B, and 7D that were significantly associated with seedling stage resistance. The three SNP markers rs12954, rs34220, and rs42447 on chromosomes 5D, 6A, and 7D, respectively, associated with resistance to Pt race PKTTS expressing potential new loci for leaf rust resistance. Overall, this research gives an integrated perspective of leaf rust resistance resources in Iranian bread wheat and recognizes new resistance loci that will be valuable to expand the set of resistance genes available to control this serious disease.

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