Shoot nodal culture and virus indexing of selected local and improved genotypes of cassava (Manihot esculenta) from Sierra Leone

摘要

Cassava (Manihotes culenta Crantz) is among major food and income security crops in sub-Saharan Africa. However, high seed dormancy and delayed germination limit seed propagation. Using traditional stem cutting causes loss of superior genotypes and decreases productivity as a result of low multiplication ratio (1:10) and viral and bacterial diseases.Thus, the aim of this study was to optimize and screen efficient in vitro protocols for rapid multiplication and production of disease-free cassava planting materials through nodal culture technique. The experiment was laid out in a 5 x 5 factorial arrangement in Completely Randomized Design with five cassava genotypes (Warima, Munafa, SLICASS 6, Coco cassada and SLICASS 7) and? five BAP supplemented MS medium (0, 0.02, 0.1, 1.0 and 2.0 mg/L), replicated three times. Results revealed that, BAP supplement significantly (p<0.001) influenced numbers of leaves and shoots compared to plantlet height growth traits of nodal cassava explants in culture. Virus indexing of infected plants from screen house using species specific primer pairs, OjaRep/EACVMRep and OjaRep/ACMVRep, confirmed the presence of East Africa Cassava Mosaic Virus (EACMV) and the African Cassava Mosaic Virus (ACMV) at an amplicon of approximately 650bp and 400bp, respectively. The study demonstrated the effectiveness of cytokinin supplemented MS medium in enhancing growth of cassava; and the adequacy and effectiveness of the PCR technique in identifying ACMV and EACMV using nodal cuttings. Future studies will involve molecular characterization of the EACMV strain(s) existing in the country.