Potential of Somatic Embryogenesis in Elimination of East Africa Cassava Mosaic Virus from Infected Cassava Cultivars in Kenya

Cassava mosaic disease (CMD) is an economically important disease limiting production of cassava (Manihot esculenta Crantz) in sub-Saharan Africa. Use of virus-free planting material is among the strategies for management of CMD. However, obtaining clean planting material for farmer-preferred varieties is often difficult. This study evaluated the efficacy of somatic embryogenesis to produce disease-free cassava planting materials from CMD-infected cultivars TME 14, Ex-Mariakani, Sagalato, Kibandameno and TMS 60444. Axillary buds of East Africa cassava mosaic virus (EACMV)-infected cassava nodal cuttings were cultured on MS salts with vitamins supplemented with 12 mg/l picloram for generation of primary somatic embryos (SE) which were subcultured onto the same fresh medium for generation of secondary SE. Primary and secondary SE were cultured separately onto MS supplemented with 1 mg/l naphthaleneacetic acid (NAA) for induction of cotyledons and subsequent regeneration of plants on MS supplemented with 0.4 mg/l 6-benzylaminopurine (BAP). Polymerase chain reaction (PCR) was used to discern the presence of EACMV in regenerated plants. Plants regenerated from primary and secondary somatic embryos were 87.6% and 93.5% virus free, respectively, with the PCR technique of viral particle detection. The virus-free plants acclimatized in the glasshouse showed absence of viral symptoms morphologically. These findings demonstrated the effectiveness of somatic embryogenesis in elimination of EACMV from infected cassava plants to produce clean planting materials.