Semi‐arid and subhumid West Africa is characterized by high inter‐annual rainfall variability, with variable onset of the rainy season, somewhat more predictable endings, and drought or excess water occurrence at any time during the growing season. Climate change is predicted to increase this variability. This article summarizes options for plant breeders to enhance the adaptation of pearl millet (Pennisetum glaucum [L.] R. Br.) and sorghum (Sorghum bicolor [L.] Moench) to climate variability in West Africa. Developing variety types with high degrees of heterozygosity and genetic heterogeneity for adaptation traits helps achieving better individual and population buffering capacity. Traits that potentially enhance adaptive phenotypic plasticity or yield stability in variable climates include photoperiod‐sensitive flowering, plastic tillering, flooding tolerance, seedling heat tolerance and phosphorus efficiency. Farmer‐participatory dynamic gene pool management using broad‐based populations and diverse selection environments is useful to develop new diverse germplasm adapted to specific production constraints including climate variability. For sustainable productivity increase, improved cultivars should respond to farmer‐adoptable soil fertility management and water harvesting techniques. Larger‐scale, on‐farm participatory testing will enable assessments of varietal performance under evolving climatic variability, provide perspective on needs and opportunities and enhance adoption. Strengthening seed systems will be required to achieve sustainable impacts.

No abstract

Diversity among 124 sorghum landraces from 10 villages surveyed in 3 regions of Burkina Faso covering different agroecological zones was assessed by 28 agromorphological traits and 29 microsatellite markers. 94.4% of the landraces collected belonged to the botanical race guinea (consisting of 96.6% guinea gambicum and 3.4% guinea margaritiferum), 74.2% had white kernels, 13.7% had orange and 12.1% had red kernels. Compared to the "village nested within zone" factor, the "variety nested within village within zone" factor predominately contributed to the diversity pattern for all nine statistically analysed quantitative traits. The multivariate analyses performed on ten morphological traits identified five landrace groups, and of these, the red kernel sorghum types appeared the most homogenous. 2 to 17 alleles were detected per locus with a mean 4.9 alleles per locus and a gene diversity (He) of 0.37. Landraces from the sub-Sahelian zone had the highest gene diversity (He = 0.38). Cluster analysis revealed that the diversity was weakly stratified and could not be explained by any biophysical criteria. One homogenous guinea margaritiferum group was distinguished from other guinea landraces. The red kernel type appeared to be genetically distinct from all other guinea landraces. The kernel colour was the principal structuring factor. This is an example of a homogeneous group of varieties selected for a specific use (for local beer preparation), mainly grown around the households in compound fields, and presenting particular agromorphological and genetic traits. This is the most original feature of sorghum diversity in Burkina Faso and should be the focus of special conservation efforts.

Africa do not adequately reflect the landraces' discrete genetic identities. Pearl millet [Pennisetum glaucum (L.) R. Br.] landraces provide To understand the dynamics of local crop diversity, nutritional quality and security under the harsh environmental conditions of Rajasthan, India. Using amplified fragment length polymor-an interdisciplinary approach is required in which the phism (AFLP), this study investigated pearl millet genetic diversity disparate elements of population genetics, environmenpatterns and related the results to farmers' local knowledge and seed tal and social aspects, farmers' own local knowledge, systems. Thirty-nine cultivars were assessed: 14 farmer landraces from and the circumstances of their seed systems, are all intewestern Rajasthan, 13 farmer landraces from eastern Rajasthan, and grated (Brown, 2000). By this approach, effective in 12 control cultivars. Shannons' information index for western (H ϭ situ conservation strategies can be developed that will 0.34) and eastern (H ϭ 0.32) Rajasthan landraces was up to 14% prevent loss of diversity in farmers' fields and help sushigher than in composite-based improved cultivars. Analysis of moletain the processes of evolution, namely, the adaptation cular variance (AMOVA) revealed that variation within landrace popuof crops to their changing environments (Brush, 1991).lations was much higher than between regional samples. In the west, intra-village variation was higher than inter-village variation. In the Pearl millet is a hermaphroditic species with strong east, variation between landrace groups bearing a specific name was protogyny and cross pollination of up to 82% (Burton, higher than intra-group variation. Gene flow, inferred from genetic 1974). Leuck and Burton (1966) have shown that wind distances between populations, was used as an indicator for seed is the main factor responsible for pollen dispersal. Pearl exchange between farmers. In western Rajasthan, seed exchange apmillet is the staple food of the semiarid state of Rajaspears to be especially dynamic, as gene flow was greater than N e m ϭ than in northwest India. The adoption rate of improved 25 among most of its populations. Farmers' knowledge of local culticultivars in Rajasthan has been relatively slow, particuvars and seed systems was, for the most part, supported by the AFLP larly in the dry western region which lies in the transition analysis. These results are relevant for in situ maintenance and breedzone of the Thar Desert (Kelley et al., 1996; Tripp and ing strategies with a view to improving traditional cultivars, specifically performance and yielding stability. K. vom Brocke, Centre de Coopé ration Internationale en Recherche Agronomique pour le Dé veloppement (CIRAD) 01 BP. 596, Ouaga-