Sugarcane Plants from Temporary Immersion Culture: Acclimating for Commercial Production

The South African Sugarcane Institute Research Institute (SASRI) has developed the technology to produce sugarcane plants via direct somatic embryogenesis in the RITA (R) temporary immersion system. After disease indexing stalks, transverse sections of the apical meristem region from each stalk are used as explants. Although the RITA (R) technology produces on average 3,000 plants/leaf roll, acclimation of the plants on a large-scale has not been fully optimized. Using Saccharum sp. hybrid N41 as a model, this study aimed to assess plant survival at SASRI and two commercial seedling nurseries. The sequence of the acclimation protocol for the RITA (R)-derived plants at SASRI was: (1) misting chamber (3 days; watered 2 min. every 3 h); (2) growth chamber (2 weeks; watered 3 min. twice a day); (3) shade tunnel (2 weeks; watered 3 min. twice a day); and (4) open air nursery (watered 5 min. twice a day). At the commercial facilities time intervals and watering regimes within this protocol were varied slightly in accordance with existing seedling acclimation methodologies. Plant survival at the SASRI site was 52% (n=465), while 35% (n=5,000) and 52% (n=3,800) survival was recorded at the two commercial seedling nurseries. Large numbers of small plants with glassy leaves and limited or no roots were produced in the RITA (R) system. These plants remained approximately 2 cm in height during subsequent growth and acclimation. Such plants may have contributed to the mortality observed in this study. Consequently, the removal of small, hyperhydrated plants would be an essential step in the commercial-scale acclimation of sugarcane produced by temporary immersion culture technology.