Development of CMD-resistant cassava varieties through mutation induction

Cassava is widely recognized as a crop of choice for climate change adaptation strategies, particularly in sub-Saharan Africa (SSA). Cassava cultivation provides an excellent opportunity to improve the income levels of small-scale farmers and is a food security crop. Despite cassava having great potential for food security and economic growth, it is bewildered by biotic and abiotic constraints such as diseases, pests, weeds, and drought. In addition to these constraints, its production has some other constraints, including toxic cyanogenic compounds, very low protein content (1–2 % dried weight) and a short fresh tissue shelf life of 1–3 days. Furthermore, traditional breeding techniques applied in cassava face several limitations; notably, high heterozygosity, allopolyploidy, low fertility, unsynchronized flowering and limited knowledge of inherited traits that have agronomic importance. All these factors make producing improved plant lines by conventional breeding a long and tedious process. In addition, the presence of an extremely narrow genetic base in some crop varieties is a significant impediment to breeding. Nevertheless, combined induced mutation techniques with in-vitro culture methods have excellent potential in breeding programs. This is an overview of the breeding techniques used for improving resistance against CMD in cassava, highlighting the biology, epidemiology, and control of CMD viruses. Other areas reviewed are the components of virus control and some strategies examined, including diagnostics and surveillance, prevention and control of infection, and management of disease through breeding and promoting varieties that inhibit virus replication and movement.