Increasing drought tolerance through selection for osmotic adjustment in wheat

In order to select successfully for complex traits involved in drought resistance, several requirements are necessary. The first objective of this work is to identify wheat lines that differ in the level of osmotic adjustment capacity using a method with which breeders can test rapidly and fairly accurately a large number of entries. The second objective was to analyse the relationship between osmotic adjustment and yield under drought stress. A spring bread wheat nursery of 144 genotypes was grown in the field under water stress and non stress conditions. The same genotypes were screened for Relative Water Content (RWC) at solute potential (Pi) of -2.5 MPa in a greenhouse experiment. An other methodology was tested in growth chamber to obtain a direct measurement of osmotic adjustment capacity. The results obtained show that (1) osmotic adjustment occurs in spring wheat in the field during drought (2) there is a genotypic variability within the nursery for solute potential at flowering (3) the correlation between yield and RWC at Pi = -2.5 MPa is low (4) the methodology of determination of osmotic adjustment capacity in growth chamber is more suitable than in the greenhouse because of the environmental effects. Furthermore, the growth chamber methodology allow the distinction between constitutive or adaptative characteristic of the osmotic adjustment. In this context, the research of molecular markers linked to osmotic adjustment capacity could be improved using this methodology.