Aspects of Salt Tolerance in a NaCl-Selected Stable Cell Line of Citrus sinensis

Abstract

A NaCi-tolerant cell lne which was selected from ovular callus of 'Shamouti' orange (Citrus sinensis L. Osbeck) proved to be a true cell lne variant. This conclusion is based on the following observations. (a) Cells which have been removed from the selection pressure for at least four passages retain the same NaCI tolerance as do cells which are kept constantly on 0.2 molar NaCI. (b) Na+ and Cl uptake are considerably lower in salt-tolerant cells (R-10) than in salt-sensitive cells (L-5) (2,3,25,28,30). Selection has commonly been practiced following exposure to salt, drought, cold, and herbicides. Of these agriculturally useful traits, resistance or tolerance to salt is becoming increasingly important among crops of agricultural value grown in arid zones. Selection of cell lines which exhibit tolerance to salt stress has been reported before (6,7,11,21)

Displacement of Ca2+ by Na+ from the Plasmalemma of Root Cells

“…Whether or not this holds true for other cultivars or species remains to be verified. Recently, differential growth responses to salinity as affected by external calcium have been observed within a species (1,24). It would be interesting to know if these differences can be attributed to differences in displacement of membrane-associated Ca2`or to some other factor.…”

Adaptation of Tobacco Cells to NaCl

“…For instance, while salt tolerant cells of tobacco accumulate Nae and Cl- (20,44), salt tolerant citrus cells accumulate less Nae and Cl-than do salt sensitive cells (1). Although most reports claim stability of the salt tolerance trait through prolonged periods of culture in the absence ofsalt (1,9,30,31,44), there are reports where tolerance was only stable in some lines (35) and we have reported a lack of stability of the salt tolerance phenotype of cells isolated in medium with 10 g L-`NaCl (18).…”

“…Cell lines with enhanced tolerance to NaCl have been isolated from many glycophytic species (1,7,9,18,24,30,31,33,35,40,44) and various physiological processes appear to contribute to the adaptation of cells to salinity. For instance, while salt tolerant cells of tobacco accumulate Nae and Cl- (20,44), salt tolerant citrus cells accumulate less Nae and Cl-than do salt sensitive cells (1).…”

“…Many of these mechanisms utilize numerous cells and tissues in a coordinated series of processes in order to effect salinity tolerance and therefore require the anatomical organization which exists in intact plants. These growing cells (1 1,13). Many halophytes have anatomical structures such as salt glands or bladders, or specialized trichomes which serve as repositories for accumulated salt and thus limit exposure ofgrowing cells to NaCl (1 1).…”

Screening of citrus rootstocks for salt tolerance in semi-arid climates - A review

“…They further reported that embryoids regenerated from salt tolerant callus survived and grew better in saline media than embryoids regenerated from the original salt sensitive callus. Further, Ben-Hayyim and Kochba (1983) determined that the NaCl tolerant ovular callus line of Shamouti orange proved to be a true cell line variant. Matsumoto & Yamaguchi (1984) studied on the development of seven salt tolerant lines from EMS treated material and found that the lines with the highest salt tolerance were derived from the material which had undergone the highest exposure to EMS.…”