Characterisation of an ethyl methanesulfonate-derived drought-tolerant sugarcane mutant line

Sustainable sugarcane production in areas prone to frequent and severe drought can be achieved by creating resilient sugarcane varieties. In this study, a unique mutant line, M9.2, was generated from a drought susceptible commercial sugarcane cultivar, N19, through the exposure of callus cells to the ethyl methanesulfonate mutagen and subsequent in vitro osmotic selection on polyethylene glycol. The study aimed to characterise the M9.2 mutant, in comparison with the parental genotype, in terms of its physiological and biochemical performance and proteome profile when exposed to moderate (14 days without water) and severe (21 days without water) water deficit stress in glasshouse pot trials. In comparison to the parental counterparts, the mutant plants were able to sustain the quantum efficiency of photosystem II (Fv/Fm) throughout the stress. Under mild stress, the mutant plants displayed elevated stomatal conductance, high concentrations of proline, accumulated less H2O2 and phenotypically displayed limited wilting and no visible signs of leaf senescence. Under severe stress, the mutant plants accumulated less malondialdehyde and more antioxidant enzymes (superoxide dismutase and catalase) than the parental line. Differential protein expression was also observed according to two-dimensional difference gel electrophoresis patterns of proteins expressed in the M9.2 mutant versus the parental plants during moderate stress. Analysis revealed proteins related to photosynthesis (pyruvate orthophosphate dikinase, un-fragmented ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit and chlorophyll a/b-binding protein 3) and carbohydrate metabolism (sucrose synthase) were up-regulated in the mutant. Differentially expressed proteins were further linked to energy metabolism, methylation homeostasis and DNA repair. This study characterises the new M9.2 mutant with beneficial drought-tolerant traits which have the potential to be exploited in future sugarcane breeding programmes.

Automated summary

A mutant line, M9.2, was generated from a drought susceptible sugarcane cultivar and showed improved drought tolerance compared to the parental genotype. The mutant plants displayed higher photosynthetic efficiency, increased stomatal conductance, accumulation of proline, and enhanced antioxidant enzymes under water deficit stress. Differentially expressed proteins related to photosynthesis, carbohydrate metabolism, energy metabolism, methylation homeostasis, and DNA repair were observed. This study characterizes the new M9.2 mutant as a potential valuable resource for future sugarcane breeding programs.