A Rapid Adaptation to Low Salinity of Inland-Colonizing Populations of the Littoral Grass Leymus arenarius

Ecological studies on salt tolerance in plants have focused mainly on population differentiation with limited information on the timescale and genetic basis of this adaptation. This study reports on rapid adaptation of the littoral grass Leymus arenarius (lymegrass) to low salinity that has been found since 1967 to colonize the roadsides studied in Finland. Roadsides offer an open microenvironment similar to that of the beach. Thirty-four roadside and littoral populations were differentiated by germinating seeds at 300 mM NaCl, ca. half-strength seawater. Seeds of inland and sub-maritime populations had significantly (P < .001) less salt tolerance than littoral populations. The shortest distances of the habitats from the seashores showed significant (P < .001) negative correlation with the germination ability at 300 mM NaCl. Electrophoretic patterns of endospermal glycosylated proteins of high-molar-mass leymins were significantly (P < .01) correlated to total germination at 300 mM NaCl. Inland populations usually had three bands of the high-molar-mass leymins, but six bands of leymins were found in seeds of the most salt tolerant population. The rapid adaptation of lymegrass seed germination to low salinity indicates that only a few genes are involved in its salt tolerance and that the activity of such genes provides a load where salt tolerance is unnecessary. Alternatively, salinity in the habitat may control the expression of some genes.