A rapid in vitro protocol using direct somatic embryogenesis and microprojectile bombardment was investigated to establish the developmental phases most suitable for efficient sugarcane transformation. Immature leaf roll disc explants with and without pre-emergent inflorescence tissue were compared. It was shown that for effective transformation to occur, explants should be cultured for several days to allow initiation of embryo development prior to bombardment. Leaf roll discs with pre-emergent inflorescences showed a higher degree of embryogenic competence than non-flowering explants, and transformation efficiency was higher when explants containing floral initials were bombarded. Despite the occurrence of high numbers of phenotypically negative plants, combining the use of inflorescent leaf roll discs with direct embryogenic regeneration has the potential to improve the speed and efficiency of transgenesis in sugarcane.

Sugarcane breeding, while key to continued improvement of pest and disease resistance and to increasing sucrose and biomass yields, is constrained by the length of time taken to release a new cultivar (10-14 yr). Forty years of international research into sugarcane in vitro culture has delivered many well-developed systems that are routinely applied to research and commercial activities, namely: (a) micropropagation of genotypes; (b) production of disease-free material from excised apical meristems; (c) international germplasm exchange; (d) generation of somaclones; (e) rapid disease and pest resistance screening; and (f) germplasm conservation. This review outlines several in vitro techniques, discussing how protocols have been tailored to address pertinent research issues and exploring possible commercial applications in the sugar industry to reduce the time frame to release a new cultivar and decrease demands on resources such as land and labour.

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