Ex vitro Morpho-Physiological Screening of Drought Tolerant Sugarcane Epimutants Generated Via 5-Azacytidine and Imidacloprid Treatments

Abstract

The present study evaluated the drought tolerance potential of ten epimutants generated in vitro via 5-Azacytidine (Azac) demethylation, followed by re-methylation in the presence of imidacloprid (IMI), both under polyethylene glycol (PEG) osmotic pressure and heat stress. Ex vitro chimera dissolution involved four rounds of repeated drought stress in the glasshouse. Most epimutant lines had significantly high Fv/Fm values (up to 0.46, 0.76, and 0.78 respectively for V2, V3 and V4 stress rounds) when compared with the stressed parent cultivar N41 control (S N41) with 0.12, 0.21, and 0.59 ratios respectively. Significant rapid growth rates (0.25 cm height increase per day) were observed in the GP4, MP1, MP5, and SP5 lines while S N41 had 0.10 cm stalk height gain per day during stress. Moreover, the percent green leaf area (GLA) values were higher (57.2–73.0%) for the epimutant lines than drought sensitive MP6 (12.4%) and S N41 (47.3%) during stress. The GP1, MP5 and SP5 lines maintained high relative water content (43–51%) than S N41 (38%) under drought conditions. Principal component and cluster analyses of morpho-physiological traits separated trait indices data and revealed that the epimutants with highest drought stress tolerance were the MP2, MP5, GP2, GP4, GP5, and SP5, and these same lines recuperated rapidly from stress. This study has laid a foundation for an alternative method of assessing sugarcane phenotypes for drought tolerance using morpho-physiological traits.