manihot esculenta starch crops cultivation 66 development 65 economics 63 productivity 61 production 54 marketing 53 root productivity 49 research 41 producción 40 cassava products 38 cultivation systems 38 pests 37 processed products 37 cultivars 33 productividad de raices 33 costs 31 plant anatomy 31 processing 29 trade 28 diseases and pathogens 27 technology 27 uses 26 mercadeo 24 prices 24 roots 24 intercropping 23 feeds and feeding 22 composition 21