QTL analysis for agronomic traits in a barley doubled haploids population grown in Iran

Seventy-two doubled haploid (DH) barley lines and their two parents 'Steptoe' and 'Morex' were planted in a randomized complete block design with three replications at the research farm of the University of Tehran, Faculty of Agriculture, Karaj, Iran, for two growing seasons. Each plot consisted of a 2 m row and was scored for 10 agronomic traits. Analysis of variance showed that the main effects of genotype and environment (year) were significant for all studied traits. Genotype by environment interaction was also significant for all the traits except for plant height and seed/spike. Heritability estimates were more than 0.6 for all of the traits. A genetic map comprising 327 molecular markers was recovered from Grain Gene and used for quantitative trait loci (QTL) mapping. This map is fairly saturated with a total length of 1226 cM and an average marker spacing of 3.75 cM. Twenty-three QTLs controlling different studied traits were identified. Phenotypic variance explained by these QTLs varies from 11.9 to 61.1%. QTLs were identified for all traits on all chromosomes except chromosome 6H. Highest LOD scores were obtained for the dates of spike initiation and flowering on chromosome 2H, and for plant height and spike length on chromosome 3H. QTLs for 1000-seed weight, an indicator of drought tolerance, were found on chromosomes 1H and 5H, with positive alleles from 'Morex', and on chromosome 7H with positive alleles from 'Steptoe'. The specificity of the QTLs for Iranian conditions as well as their usefulness for marker-assisted selection in dry conditions is discussed.