Polyethylene Glycol (Peg) Mediated In Vitro Characterization of Sugarcane (CP-77/400) Calli and Regenerated Plantlets

Abstract

Drought stress negatively affects sugarcane growth and productivity. Polyethylene glycol (PEG) serves as an indicator and inducer of osmotic stress in plants. In the present research, PEG stress was applied to sugarcane calli of CP-77/400 and the physiological and biochemical responses of the stressed and the control calli were measured. The calli were grown on MS media and were then transferred to different PEG concentrations (0%, 2.5%, 5% and 7.5%). Data was taken after 30 and 60 days of treatment. Relative growth of call showed significant decrease after 30 and 60 days. Control had maximum relative growth (3.33), while calli on 7.5% PEG showed the least growth rate i.e 1.33. Similarly, non-stressed control calli had higher water content i.e. (20%) while 7.5% stressed calli showed lowest water content i.e. (5%). Catalase activity was not significantly different between control and the stressed calli after 30 days at all PEG%. However, the catalase activity was significantly increased (0.14 µMole ml-1 min-1) as compared to that of the control (0.06 µMole ml-1 min-1) at 7.5% PEG media after 60 days of stress application. PEG stress showed a significant increase in proline content. Control calli showed less amount of proline content i.e. 1.34 µMg-¹ and 1.4 µMg-¹ while 7.5% PEG had high amount of proline i.e. 4.2 µMg-¹ and 7 µMg-¹ after 30 and 60 days, respectively. In case of sugar, a significant increase was observed when calli were exposed to PEG stress. Control calli had less sugar content (1.3 µMg-¹ and 1.5 µMg¹) while 7.5% PEG had significantly high sugar content (20 µMg-1and 27 µMg-¹, respectively). Moreover, the plantlets regenerated from the selected calli showed improved root and shoot growth on media containing 7.5% PEG. Our results revealed that invitro analysis of sugarcane calli against PEG may be a useful strategy for initial screening and selection of stress tolerant sugarcane lines to be used in the future breeding programs.