**7. Varieties and planting material**

Stakes cut from healthy stems free of pests and diseases have a higher rate of sprouting and produce higher root yields. As a result, many farmers do not save

cassava stems for planting and frequently source cuttings from neighbors or in local markets; under such conditions, assuring the quality of planting material is practically impossible. Effective systems for routine multiplication and distribution of disease-free planting material of improved varieties is essential for sustainable intensification. Although several protocols have been developed for the rapid multiplication of cassava, and could be scaled up for the dedicated production of material that meets quality standards [6], very few countries have a formal seed system for cassava multiplication.

For the production of cassava, it is essential to maintain genetic purity and use high quality planting materials that are free of diseases and pathogens. Because cassava propagates vegetatively (**Figure 4**), diseases and pests can continue for several generations.

This is a negligible problem with plant seeds. In addition, cassava cuttings are perishable, bulky, and cumbersome to transport and require significant storage space. Subsistence farmers usually harvest in small portions over a year, so storing stakes until the next planting is logistically challenging. Stakes cut from healthy stems free of pests and diseases have high germination rates and high root yields. As a result, many farmers do not preserve cassava stalks for planting and often procure cuttings from their neighbors or local markets. In such situations, it is virtually impossible to guarantee the quality of the planting material. An effective system for the daily reproduction and distribution of disease-free planting materials of improved cultivars is essential for sustainable production. Several protocols have been developed for rapid breeding of cassava and can be extended for targeted production of materials that meet quality standards [6]. Few countries have a formal stem multiplication system for cassava breeding.

To increase the efficiency of cassava stem production, IITA and Nigeria's National Root Crops Research Institute have developed a rapid multiplication technology, which involves cutting cassava stems into stakes with 2 or 3 nodes, rather than the usual 5–7. With efficient field management, cassava stems can be harvested twice a year, at 6 and 12 months after planting, yielding around 50 times more stems than were used for planting [7]. In the absence of a national cassava seed system, cassava development programmes in a number of African countries have used a 3-tier

**Figure 4.** *(a) Cassava stem (b) Planted cassava stem cuttings.*

#### *Cassava Production Enterprise in the Tropics DOI: http://dx.doi.org/10.5772/intechopen.104677*

community-based system of rapid multiplication to supply farmers with improved, healthy planting material [8]. At the top level, material from breeders is multiplied under optimal agronomic conditions on research stations and government farms to produce disease-free foundation seed. The secondary level involves further multiplication on farms often run by farmer groups, community organizations and NGOs. Certified material is then distributed to tertiary multiplication sites, which are the main and most readily accessible source of stems [9].

High participation in grassroots growth was achieved through the Great Lakes Cassava Initiative, managed by the Catholic Relief Services Foundation and supported by the Bill & Melinda Gates Foundation. It established a network of 6500 small breeding plots with an average size of 0.3 ha, each serving about 350 local farmers and contributing to the breeding of a total of 33.6 million stems. This initiative also introduced a low-cost quality control protocol based on visual assessments to assess variety purity and pest and disease assessments. The use of poor-quality planting material will remain one of the major causes of low cassava yields, especially in Latin America and Africa for some time to come. In the absence of efficient systems of multiplication and distribution, farmers can help to improve the situation using some simple local practices:


Rainfall is the only source of water for almost 80% of the world's cropland. Rainfed cassava production accounts for up to 60% of worldwide agricultural output, and millions of the world's poorest farmers rely on it for their livelihoods and food security. Irrigated agriculture produces up to three times more from the same unit area of land due to higher cultivation intensities and average yields. Agriculture, both rainfed and irrigated, faces significant obstacles. Irrigation is

under increasing pressure to produce more crops with fewer drops and to lessen its negative environmental implications, such as soil salinization and nitrate poisoning of drinking water, as competition for increasingly precious water resources intensifies. More precise water-saving methods, including drip and micro-irrigation, should be used. Rainfed agricultural production is in grave danger as a result of climate change. By 2050, most scenarios predict a 30% or more decrease in rainfall runoff across large areas of Sub-Saharan Africa, South Asia, and Latin America. Crop yields are expected to drop in many developing countries as water flows grow more erratic, and the frequency of droughts and floods rises [12]. Nonetheless, a comprehensive review of agricultural water management indicated that rainfed areas have the highest potential for productivity gains [13]. However, better and drought-tolerant cultivars should be cultivated. In addition, widespread adoption of conservation tillage, mulching, and other soil management measures, as well as land deterioration and irrigation reversal should be practiced. Cassava, unlike most other food crops, does not have a crucial period for blooming and seed formation during which adequate soil moisture is required. It also has various water-saving defense mechanisms, and its roots can reach enormous depths to access subterranean moisture stores [14]. Therefore, cassava can tolerate droughts for a long period of time [6].
