starch crops manihot esculenta 221 development 68 cultivation 67 economics 65 productivity 64 production 56 marketing 55 root productivity 50 cassava products 44 processed products 42 research 42 producción 40 cultivation systems 39 pests 37 cultivars 33 plant anatomy 33 productividad de raices 33 costs 32 processing 31 trade 30 uses 30 technology 28 diseases and pathogens 27 roots 26 feeds and feeding 25 prices 25 intercropping 24 mercadeo 24 composition 22