Selection of a mutation conferring high NaCl tolerance to gametophytes of Ceratopteris

Spores from a weakly salt tolerant strain of Ceratopteris richardii containing the mutation stl1 were irradiated and sown on nutrient medium supplemented with 200 mM NaCl. A single highly salt tolerant gametophyte was recovered and selfed to generate a homozygous sporophyte. Spores from this strain, 10a23, were used to document the sexual transmission of the trait and to monitor the inheritance of tolerance in crosses to both the wild type and to the parental salt tolerant strain. Genetic analysis showed the 10a23 strain to possess both the original stl1 mutation and an additional semi-dominant nuclear mutation, stl2, that individually conferred a high level of tolerance to gametophytes. In combination, both mutations had additive effects. Tolerance was also evident in sporophytes, but at a lower level than in gametophytes.