Salt-Tolerant California Bulrush (Schoenoplectus californicus) From Repetitive Cellular Selections: New Plant Type for Brackish Marsh Restoration.

California bulrush (Schoenoplectus californicus), a deep water marsh plant species, has been used for erosion control along shorelines, canal banks, levees, and other areas of soil-water interface. The great potential of California bulrush for erosion control, however, is limited to freshwater marshes. It can only tolerate salt concentrations of up to 6 ppt (part per thousand). The objectives of this study were to 1) develop improved salt-tolerant lines through repetitive cellular selections and 2) evaluate levels of salt tolerance among new plant types recovered from the treatments. Repetitive cellular selections involving progressive exposures to elevated salt concentrations of four successive generations of in-vitro plants have yielded viable new California bulrush lines with improved tolerance to salinity. The initial selection was done by treating individual cells to salt concentrations of 9 ppt for one month followed by regeneration of surviving cells into the plants. Viable plants were screened in the same salinity regime for three continuous months in the greenhouse. The best plant was selected to enter the same cellular collections using an elevated level of salt concentration (12 ppt). The screening process was repeated to obtain four consecutive generations. A total of 25 salt-tolerant plants capable of tolerating salt concentrations of 16 ppt was recovered. These plants are phenotypically normal. Under an average sea salinity level of 34 ppt, a typical California bulrush line could only survive for a period of 2 to 3 weeks. Even though their growth was severely affected in 34 ppt salt, these salt-tolerant lines were capable of maintaining green stems for 2 months and resume their normal growth when transferred to salt concentrations of 16 ppt or less. The availability of improved salt-tolerant California bulrush will enhance the capability to control erosion and restore degraded habitat in brackish marshes.