Genome-wide association analysis of agronomic traits in wheat under supplemental irrigation and rain-fed conditions

The yield and efficiency of wheat decreases affected by drought stress. Breeding for drought tolerance is one of the key components that enhance sustainable wheat production. Association mapping with SNP markers can be used to identify loci controlling quantitative traits (QTLs). For this purpose, 249 landraces of Iranian bread wheat from throughout Iran were collected and compared under supplemental irrigation and rain-fed conditions at the Dryland Agriculture Research Station (Kermanshah, Iran). During the growing season and after harvesting, data related to phonological, morphological and physiological traits were recorded and measured. Association analysis with MLM method identified 64 and 61 QTLs numbers in supplementary irrigation and rainfed conditions, respectively. The results showed that the linkage disequilibrium among chromosomes is variable and with increasing genetic distance, the linkage disequilibrium decreasing. Some traits were controlled by common QTLs, which is a proof of the existence of pleiotropic effects of a gene, and simultaneous selection can be done for those traits. The markers identified in this study (in supplemental irrigation conditions QTL for plant height 1125680 F|0--7:A>G|, Peduncle length 1092041 F|0--8:G>A| with 153 and 164 cM, respectively on chromosome 2B and in rain-fed conditions QTL for number of seed per spike 1087201 F|0--8:G>A|, Grain yield 2256346 F|0--21:C>T| with 251 and 15 cM, respectively on chromosome 5A) are useful genomic resources and after genotyping so that we can initiate marker-assisted selection (MAS) in wheat under drought-stressed and non-stressed conditions, and for fine mapping and cloning of the underlying genes and QTL.