SEVERAL QTLS INVOLVED IN OSMOTIC ADJUSTMENT TRAIT VARIATION IN BARLEY(HORDEUM-VULGARE L.)

Osmotic adjustment (OA) was previously demonstrated to be an important adaptive mechanism of drought tolerance in cereals. In order to deter mine which genomic regions are involved in OA variation, 187 barley (H ordeum vulgare L.) recombinant inbred lines (RILs) derived from a cros s between Tadmor (drought tolerant) and Er/Apm (susceptible) were stud ied in a growth chamber for their OA capacity (through correlated trai ts and by calculation), at an early growth stage and under two water t reatments (soil moisture of 14% and 100% of field capacity). The conti nuous distribution of the traits and their broad-sense line heritabili ties. ranging from 0.04 to 0.44, indicated that OA and related traits should have a polygenic nature. A subset of 167 RILs were also genotyp ed using 78 RFLP, 32 RAPD and three morphological markers and a linkag e map was constructed. Despite strong environmental effects acting on the traits, interval mapping and single-marker ANOVA allowed the detec tion of three QTLs for relative water content (RWC), four QTLs for osm otic potential (psi(pi)), two QTLs of osmotic potential at full turgor (psi(pi)100) and one QTL for osmotic adjustment at a soil moisture of 14% field capacity. For the irrigated treatment, only two QTLs were d etected: one for RWC and one for psi(pi)100. Two chromosomal regions w ere involved in several OA-related trait variations and could be consi dered as regions controlling OA; these were present on chromosome 1 (7 H) and chromosome 6 (6H), whereas other regions were specific for one trait. No major QTL was found. However, the genomic region involved in OA-related traits on chromosome 1 (7H) in barley seemed to be conserv ed for OA variation among cereals. Epistatic effects, with or without additive effects, acted on the traits.