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Abstract: Rethinking the logic of institutional environments aiming to facilitate agroforestry smallholders in economic development, this article compares smallholder input supply systems for crop and tree seeds in sub‐Saharan Africa and reflects on two basic challenges: (1) how to develop a large number of relevant tree crops for different agroecologies, (2) how to reach smallholders in rural areas. Policy options for improving agroforestry input supply systems are discussed, whereby our article concludes with suggestions how sectoral approaches for crop seed systems can be modified to agroforestry seed‐seedling systems. Biophysical differences have practical implications for how the logic of the ‘African green revolution’ would be translated into a corresponding revolution for agroforestry. [ABSTRACT FROM AUTHOR]

The article focuses on the role and challenges faced agro forestry in supporting food and nutritional security. Topics discussed include adoption of improvement in the productivity of staple food crops and cultivation of varieties of edible plans for diverse diets, decline in availability of forest food due to deforestation, and increasing the yield and quality of production through genetic improvement and on-farm management.

Agroforestry ecosystems may be an important resource for conservation and sustainable use of tropical trees, but little is known of the genetic diversity they contain.Inga edulis, a widespread indigenous fruit tree in South America, is used as a model to assess the maintenance of genetic diversity in five planted vs. five natural stands in the Peruvian Amazon. Analysis of five SSR (simple sequence repeat) loci indicated lower allelic variation in planted stands[mean corrected allelic richness 31.3 (planted) and 39.3 (natural),P = 0.009]. Concerns regarding genetic erosion in planted Amazonian tree stands appear valid, although allelic variation on-farm is still relatively high. [ABSTRACT FROM AUTHOR]

An understanding of the level, structure and origin of genetic variation within and among populations of tropical trees is essential for devising optimum management strategies for their sustainable utilization and conservation. Here, amplified fragment length polymorphism (AFLP) analysis was used to partition genetic variation within and among nine populations of the predominantly riverine tree, Calycophyllum spruceanum, sampled across a wide geographical range along river tributaries of the Peruvian Amazon Basin. Analysis of molecular variance (AMOVA) employed 65 AFLP markers and revealed most variation among individuals within populations (91%), although variation among populations was highly significant (P < 0.001). Calculation of genetic distances and nested AMOVA indicated a degree of structuring among populations based on geographical proximity, although clustering did not depend on geographical distance alone. No firm evidence was obtained for unidirectional seed dispersal by water playing an important role in determining genetic structure over the geographical range sampled. Implications of data for optimising genetic management of the species are discussed and areas for further study identified. [ABSTRACT FROM AUTHOR]

Gliricidia sepium provides a variety of products important for rural communities in tropical countries. Native populations in Meso-America currently form an important source of seed for distribution to farmers, but concerns centre on mechanisms which may lead to their genetic erosion, including anthropogenic dispersal and subsequent introgression from the related species, G. maculata. Populations of Gliricidia were examined genetically using approaches based on the polymerase chain reaction to test for interspecific hybridization and introgression between G. sepium and G. maculata. Analysis involved 13 RAPD and two RFLP-PCR markers which were identified to have species-diagnostic distributions. Data from both approaches corresponded and indicated three locations where multilocus genotypes were consistent with an hybrid origin. Data at one of these sites was consistent with introgression following hybridization. The hybrid origin of populations was supported by the intermediate geographical location of these sites to 'pure' populations of each species. Analysis of maternally inherited organellar DNA, which involved the detection of SSCPs in mitochondrial DNA amplification products, allowed further delineation of genetic structure among Gliricidia populations. Mitochondria1 data indicated a high degree of organelle differentiation between sampled locations and identified G. sepium- and G. maculate-diagnostic haplotypes. This data supported the interpretation of genetic structure based on RAPDs and RFLP-PCR. In addition, cytonuclear analysis allowed the directionality of gene transfer during the formation of hybrid populations to be described. Despite evidence for the occurrence of interspecific hybridization and introgression in Gliricidia, important resource populations of G. sepium on the Pacific coast appear to have retained their genetic integrity. Implications in terms of the conservation and utilization of genetic resources within the genus are discussed. [ABSTRACT FROM AUTHOR]

Presents observations about the cleaved amplified polymorphic sequence in Irvingia gabonensis and Irvingia wombolu, fruit trees indigenous to Africa. How the trees are viewed as economically important; Impact of high rates of deforestation and incorporation in agroforestry systems; View that genetic research can inform evaluation and conservation programs; Consideration of a study designed to describe the development of anonymous, nuclear, cleaved amplified polymorphic sequences (CAPS), which have been successfully applied to a range of phylogeographic and population genetic questions for I. gabonensis and I. wombolu.

An understanding of the processes that determine the observed patterns of genetic variation in natural plant populations is an important factor in the management of biodiversity. Pollen-mediated gene dispersal is recognized as a major determinant of population genetic structure. Here, the utility of simple sequence repeat (SSR) analysis was investigated for the measurement of pollen-mediated gene transfer by paternity exclusion in a restricted, fragmented and endangered population of the insect-pollinated tropical leguminous tree Gliricidia sepium located in Guatemala. Data at a single SSR locus, which revealed six allelic variants, were employed to generate minimum distance curves of pollen dispersal. Combined data from all six alleles indicated that a minimum of 1.8 percent of transfer events occurred over a distance of greater than 75 m. However, this value represents an underestimate because of the exclusion approach employed for analysis. Considering the four rarest alleles in the population only (combined frequency = 0.196), which provides a less biased indicator of gene transfer,a minimum of 6.1 percent of pollen movements could be attributed to greater than 75 m. One extreme example of gene transfer of over 275 mwas recorded. Estimates of pollen transfer suggest a homogenizing effect on genetic structure over the spatial scale of the study population and provide an important indicator for the genetic management of natural and exotic stands of G. sepium. This study provides the firstexample of SSR analysis being employed to estimate directly pollen movement in a natural stand of any tree species. [ABSTRACT FROM AUTHOR]