An in vitro radiation induced mutagenesis-selection system for salinity tolerance in sugarcane

Abstract

In vitro radiation induced mutagenesis-selection was employed for salt tolerance in popular Indian sugarcane cv. Co 86032. Radiosensitivity characterized in terms of growth rate and cell viability indicated 20 Gy as LD50 for embryogenic sugarcane callus cultures. Response of embryogenic calli exposed to different NaCl concentrations (85.6, 128.3, 171.1, 213.9 or 256.7 mM) indicated significant progressive decrease in cell viability and increase in membrane damage rate with increasing salt concentration. Based on these results, 20 Gy irradiated calli were stressed with 85.6 or 171.1 mM NaCl for selection for salt tolerance. Both irradiated or non-irradiated calli exhibited reduced growth rate compared to their respective controls, however, the extent of growth rate reduction was more in un-irradiated stressed calli. Further, in order to study the effect of auxin on salt selection, the calli were cultured on NaCl selection medium supplemented with or without auxin (2, 4-D). The growth rate was higher when NaCl media was supplemented with the auxin than that of without auxin. The calli exposed to 171.1 mM NaCl accumulated more proline than the control and 85.6 mM NaCl stressed irradiated or nonirradiated calli. Proline accumulation in the calli exposed to 85.6 mM NaCl without 2, 4-D was significantly higher than that of the calli stressed at the same salt concentration with 2, 4-D. The irradiated calli stressed with 85.6 mM NaCl medium with or without 2, 4-D accumulated more proline than the nonirradiated calli exposed to the respective salt treatments. Thus, the results suggest in vitro mutagenesis-selection as a powerful tool for enhanced tolerance to abiotic stresses, which may improve the competitiveness of the popular sugarcane cultivars and their commercial cultivation in saline areas.