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Abstract Study on in vitro cultures of ten cassava cultivars cultivated mainly in China demonstrated the significant different capacities of somatic embryogenesis (SE) and shoot organogenesis (SO) among tested genotypes. Using apical and axillary buds as explants, SE was induced on induction medium containing 12 mg/L picloram under the dark condition. After 2 weeks culturing, their SE frequencies were recorded. Among tested cultivars, NZ188, SC124 and SC205 could be over 80%. For SE induction, the effect of 12 mg/L picloram was better than that of 6 mg/L 2,4-D. Secondary SE could be established during cyclic subculturing of primary somatic embryos. Mature somatic embryos with green cotyledons could germinate and develop plantlets. The maturation frequency of NZ188 and SC8 could reach more than 80%. Using the pieces of somatic cotyledons as explants, secondary SE and SO could be induced after culturing on SE and SO induction media, respectively. The SE frequencies from somatic cotyledons of all tested cultivars achieved more than 77%. On SO medium, shoot meristems and adventitious shoots were developed after 2 weeks. The induction frequencies are between 34.7% and 72.2% among tested cultivars, and the performance of NZ188, NZ199 and SC124 are better than other cultivars. Adding ethylene inhibitor AgNO3 to the regeneration medium significantly reduced callus formation and improved the development of shoots, including regeneration rate and average shoot number per explant. AgNO3 at 4 mg/L has been considered the most suitable concentration to be used in this study. The shoots regenerated from AgNO3-containing medium grew much better and were easy for planting into soil.
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Received: 20 January 2009
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