Tolerance of Eruca sativa to Stress by Four Types of Salt

  Objectives  Eruca sativa seed germination and seedling tolerance to 4 types of salts were studied in a simulated experimentation for breeding and cultivar selection.

  Methods  Three lines of E. sativa cultivars, 15 Yunjie 4, 11 Yunjie 32-1, and 16 Yunjie 9, under the stress by 4 types of salt in varied concentrations, including 30-300 mmol·L⁻¹ NaCl, 30-150 mmol·L⁻¹ Na₂SO₄, 15-60 mmol·L⁻¹ NaHCO₃, and 5-30 mmol·L⁻¹ Na₂CO₃, were used in the experimentation. In the prepared media, the rate, potential, and index of seed germination as well as the weight, radicle length, and hypocotyl length of new shoots were determined. The critical salt concentration beyond which irrevocable damage occurred to the plant and the tolerance threshold to stress imposed by a specific salt at which a plant could still revert to normal conditions were obtained for a multiple indicator evaluation on the E. sativa lines.

  Results  (1) The least critical concentration and the tolerance threshold to the exposure of individual salt by E. sativa were found when these indicators were gauged by the radical seedling length. Therefore, the measurement was selected for the evaluation. (2) At either the alkaline Na⁺ was greater or equal to 30 mmol·L⁻¹ or the neutral Na⁺ greater or equal to 180 mmol·L⁻¹, the seed germination and seedling growth were significantly inhibited. (3) Under NaCl or Na₂SO₄ stress, 15 Yunjie 4 displayed the strongest tolerance, followed by 11 Yunjie 32-1 and 16 Yunjie 9. On Na₂CO₃, 15 Yunjie 4 was most tolerant, which was followed by 16 Yunjie 9 and 11 Yunjie 32-1. NaHCO₃ was best tolerated by 16 Yunjie 9 and followed by 15 Yunjie 4 and 11 Yunjie 32-1. And (4) among the 3 cultivars, 15 Yunjie 4 had the highest critical salt concentrations as well as tolerance thresholds in dealing with the various salts. It showed a threshold at 158 mmol·L⁻¹ on NaCl, 88 mmol·L⁻¹ on Na₂SO₄, and 16.3 mmol·L⁻¹ on Na₂CO₃, and a critical concentration on NaCl at 264 mmol·L⁻¹, on Na₂SO₄ at 30 mmol·L⁻¹, and on Na₂CO₃ at 23 mmol·L⁻¹. However, 16 Yunjie 9 exhibited a high tolerance to NaHCO₃ with the greatest threshold at 42 mmol·L⁻¹ and a critical concentration at 64 mmol·L⁻¹.

  Conclusion  The effect of stress exerted by NaCl on E. sativa seed germination was less sever than that by Na₂SO₄, and that by NaHCO₃ lower than Na₂CO₃. The NaCl and Na₂SO₄ tolerance of the cultivars were consistently ranked as 15 Yunjie 4＞11 Yunjie 32-1＞16 Yunjie 9; the NaHCO₃ tolerance as 16 Yunjie 9＞15 Yunjie 4＞11 Yunjie 32-1; and the Na₂CO₃ tolerance as 15 Yunjie 4＞16 Yunjie 9＞11 Yunjie 32-1. The information would provide a guideline for future studies on the cultivation and management of E. sativa farming on saline-alkali land.