Rapid Screening of Sugarcane Plantlets for In Vitro Mannitol-Induced Stress

Abstract

Six cultivars with a range of known field responses to drought were tested in vitro. Firstly, the two on each end of the drought tolerance scale (NCo376, most susceptible and N41, most tolerant) were screened on 204–1493 mM mannitol for  % re-rooting after 10 days, following plantlet root trimming. From the results, the LD₅₀ and LD₉₀ of re-rooting were calculated as 332 and 606 mM mannitol for NCo376 and 851 and 1493 mM mannitol for N41, respectively. These mannitol concentrations were then used as benchmarks for testing four other cultivars. At 606 mM mannitol, % re-rooting in vitro was: N41 (80 ± 10.7), N26 (80 ± 10.7), N36 (60 ± 13.1), N12 (60 ± 13.1), N19 (20 ± 10.7) and NCo376 (13.3 ± 9.1) (p < 0.05). The consequent ‘ranking’ in terms of mannitol tolerance in vitro matched well with those of field observations for drought tolerance, with N41 being the most drought tolerant and NCo376 the most susceptible. Other parameters assessed as possible drought indices such as leaf chlorophyll content (by soil plant analysis development measurements) and histochemical staining were difficult to perform on the small in vitro leaves, and relative electrolyte leakage did not distinguish drought tolerant from susceptible cultivars. Therefore, the re-rooting assessment provides a rapid (3 weeks) ranking measure and has potential application when screening mutagenic and genetically modified lines.