Mapping OTLs for Traits Associated with Barley Grain Malt in Drought Stress Conditions

Abstract

To investigate variation and detect the genomic regions controlling quality and quantity of malt extract in barely, a study was conducted using a set of 72 double haploid barley lines as well as their parents (Steptoe and Morex) in RCBD with two replications during the cropping season 2011-12. Different characteristics including germination energy, total percentage of germination, seed dormancy, seed protein, seed malt extract, seed hull, hectoliter weight, seed plumpness, plant height, days to heading, spike length, seeds per spike, peduncle length, one thousand kernels weight, grain yield and harvest index were measured. QTL analysis was done using composite interval mapping (CIM) method for each trait by means of two environments and multiple interval mapping (MIM) method was exploited for assessment of significant interactions between loci, additive × additive epistasis and testing major effects of detected QTLs at a multiple regression model. For most of traits, transgressive segregation was observed in both positive and negative directions. A total total of forty-nine QTLs with LOD ≥ 2.5 (LR ≥11.5) were identified. Explained genetic variance by these QTLs varied from 27.74 to 81.42% and maximum LOD for the QTL controlling seed plumpness was obtained on chromosome 3H (Qplum3H) with a LOD = 9.08. The largest single QTLs belonging to the quantity and quality of barley grains malt were located on chromosomes 1H, 2H, 3H, 4H and 7H. Seven additive × additive epistatic effects between identified QTLs were significant. The results revealed that water deficit compared with the location, had a significant role in the manifestation of malt quality traits. Meanwhile, in the studied haploids and their parents great variation was observed in terms of quantity and quality characteristics of barley malt. This variation can be exploited for different breeding purposes. In addition, identified stable and clustered QTLs could be used for qualitative and quantitative traits of barley malt in marker assisted selection (MAS). However, some detected markers can be identified as an informative marker for selection and increment of the concentration in the final malt extract and malt performance.