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Genetic Change in Farmer-Recycled Maize Seed:A Review of the EvidenceMichael L. Morris, Jean Risopoulos, and David BeckIntroductionObjectives of the paperThis paper summarizes what is known about farm-level maize seed management practicesand reviews the theoretical and empirical evidence regarding the relationship betweenfarmers’ seed recycling practices and the germplasm content (and agronomic performance)of maize cultivars. The focus is on farmers in developing countries, many of whom do notreplace their seed annually with newly purchased commercial seed but rely instead onrecycled seed saved from their own harvest or obtained from other farmers.The paper is divided into four parts. The remainder of this introductory section explainswhy the issue of seed recycling in maize merits attention. The second section reviews theliterature on farmers’ varietal and seed management practices in an effort to determinewhether maize seed recycling is widespread. The third section examines the relationshipbetween farmers’ seed management practices and the agronomic performance of maizecultivars, taking into account both the predictions of quantitative genetics theory, as well asempirical evidence collected in farmers’ fields. The fourth and final section summarizes themain findings. Implications for research impacts evaluation are spelled out in the appendix.Maize in the developing worldMaize is the world’s most widely grown cereal and is the primary food staple in manydeveloping countries. In 1990, of 58 million hectares planted to maize in non-temperateregions of the developing world, approximately 25 million hectares (43%) were planted tomodern varieties (MVs), including both improved open-pollinated varieties (OPVs) andhybrids (López-Pereira and Morris, 1994). 1 The widespread diffusion of maize MVs atteststo the success of the many organizations that are engaged in crop improvement andtechnology delivery, including national maize breeding programs, government agriculturalextension services, and public and private seed companies.While there is reason to be encouraged by the fact that half of the developing world’s nontemperatemaize area is planted to MVs, concerns can justifiably be raised by the fact thatthe other half is still planted to local varieties (also known as landraces) that have notbenefited from formal plant breeding efforts. Looking back over the global history ofchanges in the kinds of crop varieties that farmers grow, it is apparent that maize has1The term modern varieties (MVs) as used here refers to cultivars developed since 1960. For maize, this includes bothimproved open-pollinated varieties (OPVs) and hybrids. For rice and wheat, it includes mainly semidwarf varieties.Traditional varieties (TVs) refers to landraces (also known as local varieties) that have never been worked on by a formal plantbreeding program, as well as older improved OPVs and hybrids. As Byerlee (1994) has pointed out, the term modern varietyis something of a misnomer, since some MVs are now more than 30 years old. It is preserved here, however, to maintainconsistency with other publications. The term high-yielding varieties (HYVs), which is often used to refer to the samevarieties, is equally inaccurate, since many MVs were bred for characteristics other than yield potential.1