Wheat seedlings growth response to water deficiency and how it correlates with adult plant tolerance to drought

Improving resistance to water and osmotic stresses at the seedling stage is becoming a much more important target for wheat breeders due to an increase in the frequency and severity of drought occurrences at the crop establishment and tillering phases in many wheat growing areas of the world. Ninety-six diverse wheat genotypes were laboratory tested for germination and growth response under osmotic stress induced by polyethylene glycol (PEG). Germination percentage, mean germination time, coleoptile length, shoot length and shoot growth rate were compared under stress (-0.4 MPa) and control (0.0 MPa) conditions. The same genotypes were previously grown in field trials exposed to drought stress during the anthesis and/or grain filling growth stage along with control (optimum) conditions. Grain yield (GY) and 19 other traits of agronomic importance (earliness, stem-related traits, number of kernels, mass of 1000 grains, etc.) were recorded. All seedling traits under PEG-induced water stress showed the highest relationship with the stem and stem-related traits of adult plants. To study the correlation between stress tolerance in the seedling and reproductive stages, three stress indices (tolerance index (TOL), stress susceptibility index (SSI) and stress tolerance index (STI)) for the seedling traits and GY under pre- and post-anthesis drought stress were calculated, based on a mean trait value obtained under stress and the corresponding trait value under control conditions. The ranking of the genotypes based on TOL and STI from seedling traits was found in most cases to be significantly correlated with the ranking of genotypes based on TOL and STI from GY, respectively