manihot esculenta starch crops 221 cultivation 105 development 95 marketing 91 productivity 90 research 85 variedades 81 economics 80 production 77 root productivity 69 processing 67 cultivars 62 fitomejoramiento 60 producción 60 pests 56 mercadeo 55 processed products 55 cassava products 54 cultivo 48 costs 47 cultivation systems 47 uses 46 plant anatomy 45 productividad de raices 45 roots 44 technology 42 varieties 41 drying 40 pest control 40