Bananas, plantains, cassava, potato and sweet-potato, as well as other indigenous African root vegetables are key in solving Africa’s food and income security challenges. The total production of these crops almost doubles that of maize, rice and wheat in Africa. These vegetatively propagated crops are an excellent source of cheap energy and are a key staple foods in Sub-Saharan Africa. The importance of these crops is well known for example East African Highland bananas in the African Great Lakes region, and Cassava and Plantains in West Africa. Some cultivars are very nutritious because they are rich in vitamins or essential minerals. Research shows that a family of five could meet their annual vitamin A requirements from only a small 10 x 50 meter plot of recently developed orange flesh sweet-potato, even at low yield levels of around 5 tonnes per hectare.
Root and vegetative crops such as these are mostly produced, processed, and traded in farm households or locally, making them less vulnerable than grain to abrupt price changes in international markets. Cassava and sweet-potato can be grown in marginal conditions and nontraditional areas, and can be produced with relatively few inputs because of their ability to tolerate many abiotic stresses such as drought or heat or poor soils. In some agro-ecosystems, they often complement cereals to cut risk and make more efficient use of resources by providing food earlier in the farming calendar or by be planted in otherwise fallow periods between grain crops. They are also known as “famine crops” because of their particular role during the “lean or hunger season” when their tuberous roots can be harvested as needed to meet shortfalls in grain. and other vegetative crops. A uniquely African Green Revolution requires urgent improvements in the supply of new and improved cultivars of these vegetative crops.
Multiplication and dissemination of new varieties requires new innovation in greenhouse, tissue-culture, micro-propagation and decentralized field multiplications of healthy planting materials. In Africa today, farmer or commercial multiplication of these crops is very low compared with multiplication of cereal and pulse seed. Most planting materials used by farmers are often of poor quality because they are infected with pests and diseases, which perpetuate (and exacerbate) pest losses through successive growth cycles. Newly developed higher yielding, or disease and pest tolerant cultivars, have not been made available in sufficient and reliable quantities to satisfy the demands of African growers.
The best strategy to deliver healthy planting materials for vegetatively propagated crops includes micro-propagation of healthy propagules of selected germplasm along with multiplication in greenhouses, shade-houses and field plots. Micro-propagation is the process of growing tissue culture for plant shoot-tips in a laboratory until they are ready for transplant into the field. This propagation system significantly reduces pathogen incidence and may dramatically improve yield when coupled with good agronomic practices. Micro-propagation systems can easily include quality control to ensure certification and delivery of “clean” propagules. Tissue culture-derived materials can rapidly grow, helping the introduction of newly bred germplasm at reasonable cost and speed. They are also amenable to biological enhancement (e.g. with endophytes that extend the benefits of “clean” planting material) before delivery to farmers. Macro-propagation will be further use to multiply additional clean planting material locally and at a lower cost. However, when re‐infection rates are high, a continual supply of new planting material will be a must for annual or biennial replanting or these vegetatively propagated crops.
Phytosanitary testing to support schemes for certifying the quality of such materials throughout the production chain will be also a key element for this rapid multiplication system. The production, conditioning, and marketing of certified planting materials will be the responsibility of the public or private grower but the certifying agency must verify that they follow the approved regulations outlined by the national authority to meet the required standards for certification.