摘要：Improving smallholder access to new crop varieties haslong been recognized as a critical step for increasing agricultural productivity insub-Saharan Africa. Adoption of improved varieties that resist pests and droughtcan often raise yields even when farmers are unable to adopt more costly inputssuch as chemical fertilizer. Over the past 30 years, substantial resources have been invested in crop breedingprograms at international and national research centers serving Africa, andhundreds of new varieties have been released. However, except for a fewcommodities such as hybrid maize in southern Africa, sustained adoption ofimproved varieties has been very limited.One explanation given for the lack of adoption is the inefficiency of seed supplysystems put in place by governments in the 1970s and 1980s. These usuallyconsisted of single distribution channels dominated by public agriculturaldepartments, parastatals, or large private seed companies. Beginning in the late1980s, many countries introduced economic reforms that included liberalizationof the seed industry. Little is known about how these reforms have affected seedsector structure and performance, in particular how smallholder access toimproved seed has changed.
