Ethyl Methanesulfonate Mutagenesis and In Vitro Polyethylene Glycol Selection for Drought Tolerance in Sugarcane (Saccharum spp.)

Abstract

Drought is a serious agronomic problem, and urgent attention to overcome drought stress is vital to eradicate or minimize its effects on crop production. Random induction of genomic mutation is a technique that can enhance genetic diversity leading to useful traits such as enhanced drought tolerance. In this study, sugarcane callus was exposed to different concentrations of the chemical mutagen, ethyl methanesulfonate (EMS). Concentrations of 20 mM and lower were identified as useful to induce genomic mutations without compromising in vitro sugarcane plant regeneration abilities. Furthermore, sugarcane callus was exposed to varying concentrations of polyethylene glycol (PEG) for different time periods in order to identify a suitable in vitro osmotic selection regime to simulate drought stress in vitro. The optimal in vitro osmotic selection treatment was identified as callus exposed to 20% (w/v) PEG6000 for 8 weeks, followed by a 2 weeks osmotic recovery period without PEG and ending with a further 8 week PEG selection period during somatic embryo regenerations. Sugarcane callus from the NCo310 cultivar was subsequently mutagenized with 16 mM EMS and in vitro selected on 20% (w/v) PEG6000, which resulted in the survival of 18 plantlets. These in vitro selected lines were subjected to preliminary greenhouse pot trials to confirm drought tolerance. Pot trials identified seven lines that outlived NCo310 control plants. In addition, when re-watered after the drought stress period, plants from one mutant line recovered and were able to form new shoots. The results from this study indicate, therefore, that EMS mutagenesis and in vitro selection for osmotic pressure using PEG can be successfully applied to cultivate sugarcane plants with improved morphological and physiological responses to water stress.