Either embryogenesis or indirect organogenesis in sugarcane: are we missing the key points?

Abstract

Both in vitro establishment and callogenesis of sugarcane allow a production of quality regenerative material, which is necessary for in vitro clonal propagation and for genetic transformation. In this study, we establish the efficient production of calli from the RB855156, RB92579 and RB867515 cultivars and characterize their regenerative potential in relation to either an embryogenic or an organogenic origin both by morphology and by anatomy. Callogenesis was induced in MS medium with 3.0 mg L-1 2.4-D. Three antioxidants were tested: polyvinylpyrrolidone (150; 300; 600 mg L-1), citric acid (7.5; 15; 30; 60 mg L-1), and ascorbic acid (7.5; 15; 30; 60 mg L-1). The morphological characterization of the calli was performed by visual classification, and the anatomical analyses by light microscopy. The experimental design was completely randomized, containing 150 explants by cultivar to antioxidant evaluations and potential regenerative evaluation within three times of subcultures (84; 112; 140 days). We have attained the key points of our in vitro research. Calli regeneration depended on the oxidation level and genotype. Antioxidants only in the culture medium were not enough to prevent oxidation. However, citric acid (7.5 mg L-1) as a pretreatment of the explant minimized this problem. Bacterial contamination was developed for the three cultivars, inhibiting the establishment to RB867515. The disinfestation protocol was efficient for RB855156 and for RB92579 cultivars. Three varieties of calli differed in the regeneration potential. In addition, histological analysis of the calli unfolded not only that there were structural differences but also that their buds had an organogenic origin.