The phenotypic variation in osmotic adjustment (OA) capacity of five Bulgarian winter durum wheat genotypes and their progenies was determined using a modified method based on the measurement of seedling growth suppression after three-day exposure to osmotic stress induced by 1 mol/L sucrose. The genetic parameters of the studied trait in a diallel crossing scheme, including the selected genotypes and the microsatellite polymorphism at 43 loci, were determined. The old Bulgarian cultivar Apulicum 233 and all hybrid combinations involving this genotype showed higher OA. In the heritability of osmoregulation ability, the non-additive gene effects (specific combining ability) strongly predominated over the additive ones and had a significant impact on the observed high heterosis effect. Distinct polymorphisms were identified between the studied genotypes. Cluster analysis of the phenotypic data obtained from a multiyear test under water-limited conditions and the molecular data, both based on Euclidean distance, showed similar grouping of the genotypes with specific separation of cultivar Apulicum 233 (high OA) in a single cluster. Principal component analysis revealed not only interrelationships between the important agronomic and morpho-physiological traits in Bulgarian durum wheat under water-limited conditions, but also presence of relations between them and some microsatellite loci located near or within known quantitative trait loci (QTLs) for these traits. Further studies based on segregating population between genotypes with contrasting levels of OA will allow mapping QTLs for phenotypic traits expressed under water deficit and isolation of genes that can be used as potential markers in marker-assisted selection for drought tolerance.
Keywords: SSR markers; durum wheat (Triticum durum Desf.); heritability; osmoregulation; principal component analysis (PCA).