In vitro selection, regeneration and characterization of NaCl-tolerant plants of Sapindus trifoliatus: an important multipurpose tree

The present study demonstrates the selection of NaCl tolerant callus line and regeneration of NaCl tolerant plants of Sapindus trifoliatus L. from selected callus via somatic embryogenesis. Callus induced from leaf disc explants was subjected to the selection of NaCl-tolerant callus line on MS medium containing NaCl. The exposure of embryogenic callus to NaCl (0–250 mM) allowed the selection of callus to tolerate 100 mM NaCl, and it confirms with stability test by the three consecutive transfers of 100 mM NaCl tolerant callus to a medium devoid of NaCl and re-transfer to 100 mM NaCl supplemented medium. NaCl selected and non-selected embryogenic callus lines were characterized by the analysis of callus growth, tolerance index, and accumulation of both inorganic (Na+ and K+) and organic (proline, glycine betaine and soluble sugars) content. 100 mM NaCl-tolerant callus showed the formation of globular structure, which differentiated different stages of somatic embryos on a maintenance medium containing NaCl (0-200 mM). Mature cotyledonary stage somatic embryos developed from 100 mM NaCl tolerant globular structure were germinated on germination medium containing NaCl. About 67 and 38% NaCl tolerant somatic embryos were germinated on a medium without NaCl and containing 100 mM NaCl, respectively. NaCl tolerant plants developed on different germination medium with NaCl survived when transplanted to 0.2 or 0.3% (w/w) NaCl mixed potting mixture. Six-month-old established 100 mM NaCl tolerant plants were characterized by analyzing various physiological and biochemical parameters i.e., chlorophyll, carotenoid, L-proline content and antioxidative (MDA, SOD, CAT and APx) activities. The results suggest that in vitro selection technique offers an efficient way to develop NaCl tolerant plants of S. trifoliatus.