Regulation of somatic embryogenesis in long-tern callus cultures of sugarcane (<em>Saccharum officinarum</em> L.).

Embryogenically competent callus was induced from in vitro grown Saccharum officinarum L. (NCo 310) plantlets by plating young leaf segments on MS basal medium supplemented with 30 μM dicamba for 21 d in darkness, and subsequently transferring to a medium (EFDM) on which embryos could form and develop. Embryogenic response was improved if the EFDM was supplemented with 1 or 5 μM dicamba, casein hydrolysate (1 g l-1), and 6% maltose or 6-9% corn syrup. Calli maintained their embryogenic competence for up to 16 months under these conditions, and with alternate weekly subcultures on to fresh media containing 20 μM and 30 μM dicamba in the dark, embryogenic callus proliferation could be further increased. Additional improvements in embryogenic competence were optimized to over 40 months when primary callus was alternately precultured at weekly intervals either with 10-5 M ABA or 5% sorbitol and then transferred to a medium containing 20 or 30 μM dicamba during maintenance. In general, medium plant growth regulator and nutritional cues, especially dicamba concentration, maltose/corn syrup levels and ABA/sorbitol preconditioning, were observed to influence critically both embryogenic callus proliferation and the frequency of somatic embryogenesis. The data are discussed within the context that these treatments can be successfully manipulated to enhance long-term embryogenic competence and high-frequency somatic embryogenesis in sugarcane. [ABSTRACT FROM AUTHOR]