Drought-adaptive mechanisms involved in the escape/tolerance strategies ofArabidopsis Landsberg erecta and Columbia ecotypes and their F1 reciprocalprogeny

Arabidopsis ecotypes. Landsberg erecta (Ler) and Columbia (Col) display dif ferential drought-adaptive strategies when subjected to a progressive droug ht stress, a procedure designed to address specific, genetically determined , adaptive potentialities: Ler exhibits an escape strategy (early flowering and bolting, high sensitivity of the rosette leaves to water deficit leadi ng to leaf senescence), whereas Col withstands water stress by drought tole rance (higher biomass allocation to vegetative organs, root to shoot ratio, drought rhizogenesis Intensity, RWC, and WUE). The traits characterising t he escape strategy in Ler, like the traits associated with Col drought tole rance, were inherited as phenotypically dominant in one or both of their F1 progeny. Reciprocal effects, often paternal, were observed in the F1s. The hybrids thus displayed both types of parental strategies which could have conferred enhanced drought adaptability upon them. The pattern of inheritan ce of the drought-adaptive traits in the F1s demonstrated that the differen tial strategies, escape/tolerance, of the parental lines cannot be attribut ed to their differential programme of development. Our results highlight a wide phenotypic plasticity of Col.