The 2012 ASHS Annual Conference

Cassava is one of the most important foods in the human diet in the tropics, where it ranks fifth as a source of energy, after rice, sugar cane and maize. Since it is a vegetative propagated crop, the use of in vitro propagation is very important to preserve germplasm free of pest and diseases. Micropropagation protocols published so far indicate large differences in shoot and root development for different accessions in response to a specific medium. The establishment of a culture medium efficient for a large number of genotypes remains one of the great challenges. The objective of this study was to evaluate the performance of different cassava genotypes under different culture media in order to establish a comprehensive protocol. Six contrasting cassava genotypes were cultured on ten different media, with different combinations of hormone concentrations (IAA 0 and 1 mg/L; NAA 0, and 0.02 mg/L; BA 0.1, 0.01, and 0.05 mg/L; GA 0, 0.1, and 0.05 mg/L) and the addition of adenine sulfate (50 and 100 mg/L). For each genotype and medium, apical and axillary node explants from approximately two-month-old in vitro cultures were placed in six magenta vessels; three vessels with apical nodes and three vessels with axillary nodes. The cultures were evaluated for different phenotypic characteristics after six week. The genotypes showed different performance with significant growth differences among the different media. The apical explants grew faster and produced more biomass in the roots and shoots than the axillary explants. The different behavior of genotypes can be attributed to their origin, different genetic structure (native and improved accessions), contrasting levels of hormones (NAA, BA, and GA), and absence or presence of adenine sulfate. Two different medium compositions appeared to produce similar numbers of roots and shoots in all six accessions used in that study. The suitability for other genotypes will be tested in future experiments.