A total of ten kinds of callus were screened on 1.2% (12 g/l) and 1.6% (16 g/l) NaCl selection mediums to investigate the viable clone frequency at each passage. The relationship between the viable clone frequency and the number of the passages on the selection medium demonstrated that in one type, the viable clone frequency became stabilised at passage three or passage four, while in another type, the viable clone frequency decreased from passage one to passage five. At least two types of cell, (instantly dying cell (ID) with its frequency about 99.99% and salt adapted cell (SA) with its frequency ranging from 10-5 to 10-6) existed in all the calli studied. An additional type of cell (salt tolerant cell (ST)) was found in two calli on 1.2%, NaCl selection medium with its frequencies 0.88 x 10-6 and 12.99 x 10-6 respectively. A revised in vitro salt tolerant cell selection protocol was proposed.
Liua, P., & Baob, W. (1998). Cell types in the wild type callus of rice (Oryza sativa L.) as revealed by screening for salt tolerant lines with selection pressure. Plant Science, 131(2), 195–202. https://doi.org/10.1016/S0168-9452(97)00212-4