N. Haq

Evidence for anthropic selection of the Sheanut tree (Vitellaria paradoxa)

The Sheanut tree (Vitellaria paradoxa Gaertn.), a multi-purpose species highly valued for the oil obtained from its seeds, is commonly maintained in the semi-arid parklands of sub-Saharan West Africa. An inventory in the West Gonja District, Northern Region, Ghana, revealed that on intensively farmed land this species constituted 79.7 ± 7.2% (Basal area = 2.19 ± 0.64 m2 ha−1) of the woody biomass, on low intensity farmland 84.2 ± 10.0% (2.16 ± 0.57 m2 ha−1) and only 10.2 ± 3.3% (0.92 ± 0.23 m2 ha−1) in unmanaged woodland, with similar environmental characteristics. No significant differences were found between total Sheanut tree densities on different land use intensities, although as a proportion of all trees surveyed, large trees were more common on farmed land. Participatory surveys revealed that these populations are a direct result of anthropic selection as local farmers eliminate unwanted woody species on farmland, leaving only those Sheanut trees that meet criteria based on spacing, size, growth, health, age and yield. Characteristics that could affect population dynamics during traditional management and harvesting including short viability seeds and cryptogeal germination are also discussed with reference to unconscious selection. Tree improvement is currently constrained, as true to type varieties are difficult to propagate. It is proposed that Sheanut trees on farmland are semi-domesticated having been subject to long-term anthropic selection during cycles of traditional fallow and crop cultivation.

Underutilised crops: trends, challenges and opportunities in the 21st Century

Plant biodiversity represents the primary source for food, feed, shelter, medicines and many other products and means that make life on Earth possible and enjoyable (WCMC, 1992; UNEP 1995). The number of plant species used by humans around the world (Table 1) is only one third of the number of species which generations of diverse cultures around the world have drawn upon to develop crops that would meet specific needs. The centres of diversification of most common cultivated species are known today (Zeven and de Wet, 1982), but for many other species of local importance, the knowledge on the distribution of their genetic diversity and use patterns are still largely limited. Increased reliance on major food crops has been accompanied by a shrinking of the food basket which humankind has been relying upon for generations (Prescott-Allen and Prescott-Allen, 1990). This nutritional paradox (Ogle and Grivetti, 1995) has its roots in the agricultural “simplification”, a process that favoured some crops instead of others on the basis of their comparative advantages for growing in a wider range of habitats, their simple cultivation requirements, easier processing and storability, nutritional properties, taste, etc.

Diversity of the Sheanut tree (Vitellaria paradoxa C.F. Gaertn.) in Ghana.

The Sheanut tree (Vitellaria paradoxa C.F. Gaertn.) is highly valued for oil obtained from its seeds and frequently maintained in the semi-arid parklands of sub-Saharan Africa from Senegal to Uganda. Although variation has been noted for V. paradoxa subsp. paradoxa, few studies have been undertaken on patterns of phenotypic or genotypic diversity. Results are presented from 294 accessions collected in Ghana, using easily quantifiable morphological parameters. Productive mature trees varied from shrubby multi-stemmed individuals (height <5 m) to 30-m straight-boled trees with high compact canopies. The leaf lamina (tree mean ±% coefficient of variation of total mean) varied from 9.2 to 22.5 cm (±15.0%); seed length from 1.74 to 3.74 cm (±11.7%); and fat content from 29.1 to 61.9% of dry kernel weight (±9.4%). Clinal trends significantly correlated with location parameters that in turn related to environmental variation. Population variation of seed characteristics increased to the Northeast, perpendicular to the annual movement of the inter-tropical convergence zone. It is proposed that this is a consequence of past climatic changes, coupled with a lack of methodical selection for seed type when trees are maintained on agricultural land. Isozyme analysis revealed moderate to high levels of heterozygosity (He 0.2142) and high geneflow (Fst = 0.0124, Nm = 19.9), supporting results obtained from morphological studies. Isozyme and multivariate morphology analyses showed similar but weak geographical separation patterns.

Identifying the global potential for baobab tree cultivation using ecological niche modelling

The benefits provided by underutilised fruit tree species such as baobab (Adansonia digitata L.) in combating increasing malnutrition and poverty become more apparent as awareness grows regarding concerns of climate change and food security. Due to its multiple uses, its high nutritional and medicinal value, drought tolerance and relatively easy cultivation, baobab has been identified as one of the most important edible forest trees to be conserved, domesticated and valued in Africa. In order to contribute towards the cultivation of the species, suitability of sites in Africa and worldwide was evaluated for potential cultivation using species’ locality data and spatial environmental data in MAXENT modelling framework. A total of 450 geo-referenced records of the baobab tree were assembled from herbarium records, commercial firm’s databases and fieldwork for modelling site suitability for global cultivation of the baobab tree. Climatic and topographic data were acquired from the Worldclim data while soil data was obtained from the Harmonized World Soil Database. MAXENT was found to be a successful modelling method for studying cultivation potential. The main variables that contributed towards predicting baobab’s global cultivation potential were annual precipitation and temperature seasonality. Results suggest that baobab tree could be widely cultivated in most countries in southern Africa and in the Sudano-Sahelian zone of West Africa from Senegal to Sudan. Angola and Somalia were found to be highly suitable for cultivating baobab in Africa. Model suggests, India, where the baobab tree already exists and is used, to be the most suitable country for baobab cultivation outside Africa. North-west Australia, Madagascar, north-east Brazil and Mexico resulted to be other suitable places for cultivating the tree species. Although it is recommended model results be validated with in situ seedling experiments, there seems to be a great potential for the cultivation of this species globally.

Protoplast isolation, culture and plant regeneration in the winged bean, Psophocarpus tetragonolobus (L) D.C.

Protoplasts have been isolated from winged bean (Psophocarpus tetragonolobus) suspension culture cells using a 2-mercaptoethanol supplemented enzyme solution. These protoplasts can be induced to divide and by continued proliferation give rise to callus colonies. Shoots have been regenerated from this callus. These shoots can be rooted and subsequently the plantlets develop to maturity.

Comparative study on baobab fruit morphological variation between western and south-eastern Africa: opportunities for domestication

The baobab tree (Adansonia digitata L.) is one of the key species for domestication in the semi-arid regions of Africa. In order to help select superior materials for cultivation, fruit morphological variation focussing on pulp content was studied in two physically isolated genetically different baobab populations: Mali and Malawi (West and south-eastern Africa, respectively). In each country eight study sites were selected following a climatic gradient, and their fruit characteristics were measured. Fruit morphology was correlated with climatic and soil data. Significant differences in fruit characteristics between countries and study sites within one country were observed. In general, fruits from Mali tended to be more elongated and their seeds were lighter than those from Malawi. Some sites had significantly high fruit weight and pulp percentage. The general trend (in both countries) was the hotter the environment the lower the pulp percentage, the more spherical the fruits and the smaller the seeds. Moreover, the wetter the environment, the higher the pulp percentage. Results from this study suggest that both genetics and the environment play roles in baobab fruit morphology. Although further research is needed to confirm whether baobabs producing desirable fruits keep producing the same fruits when grown in another environment, it seems that there is room for selecting high quality planting materials.

Variation in baobab ( Adansonia digitata L.) leaf morphology and its relation to drought tolerance

The baobab tree (Adansonia digitata L.) is a valued savannah tree. Although variation in fruit characteristics of this tree have been studied, no studies to our knowledge have been carried out on variation of leaf morphology which can be linked to drought adaptation mechanisms. Accessions of baobab from different ecosystems in Benin were characterised for leaf size and thickness, stomata size and density on the abaxial surface of leaves. Significant variation was found in leaf size and stomata characteristics. Trees from northern study sites had higher stomata density and smaller guard cell length than those from southern study sites. The results show that pruning has a significant effect on leaf size, but not on stomatal characteristics. Trees from northern study sites showed more xerophytic characteristics than those from the south. It seems that genetic and physiological effects may play a role in baobab drought adaptation.

Fertility and segregation of the amphidiploid Phaseolus vulgaris L. x P. coccineus L. and its behaviour in backcrosses

SummaryAmphidiploidy was induced by colchicine treatment of cuttings from the F1 interspecific hybrid Phaseolus vulgaris L.♀ x Ph. coccineus L.♂. Pollen stainability rose from about 50% in the raw amphidiploid to 76% in some C5 individuals; similar improvement in seed fertility was also observed. It is suggested that both genic and chromosomal factors are implicated in the control of fertility in the amphidiploid.The amphidiploid is apparently unable to cross successfully with either parental species; difference in ploidy level is apparently an effective isolating mechanism between the amphidiploid and its parents.

Variation of pomelo (Citrus grandis (L.) Osbeck) in Nepal and participatory selection of strains for further improvement

A farmers’ participatory survey was carried out in the mid-hill and plain (Terai) regions of Nepal to assess the diversity, consumers’ preference for fruit quality and potential for selection of elite pomelo clones. A wide variation of morphological characters of tree, fruit, leaf and seed was identified from information gathered and from laboratory analysis. Multivariate analysis of the data produced five discrete groups, which were represented by plants from different agro-ecological regions and soil types. The groups differed significantly in yield efficiency, fruit shape and size, pulp, juice, total soluble solids and acid content, seed number, leaf shape and size. Some fruit characters, such as yield, size and acid content were found to be affected by environment and genotype, whereas others, such as fruit shape, pulp colour, seed number, bitterness were not affected by environment. Leaf shape and petiole wing shape were also not affected by the environment. Farmers were more interested in quality characteristics rather than to aspects of yield. Six superior types were identified.

Assessing morphological and isozyme variation of jackfruit (Artocarpus heterophyllus Lam.) in Bangladesh

A farmers’ participatory survey was carried out in five different agroecosystems of Bangladesh to obtain information on the genetic diversity, consumers preferences for fruit quality and to assess the data to select potentially superior genotypes of jackfruit (Artocarpus heterophyllus Lam.). A wide variation in morpho-agronomic characters was identified from farmers’ information and also from laboratory analyses. Multivariate analysis of the data produced four discrete groups, represented by trees from different agroecological zones and soil types. Characteristics such as weight; length; diameter; girth of fruits; number of bulbs per fruit; percentage of pulp; percentage of rachis (core); and percentage of rind (peel) were found to be poorly correlated with environmental factors indicating that these characters may be genetically controlled. Other characters, such as seed weight, bulb weight, and brix (%) were found to be affected by environmental and genetic factors. Isozyme analysis of 50 accessions confirmed results obtained from field studies of morpho-agronomic characters. Ten potentially superior types were selected on the basis of yield, fruiting season, flesh colour, texture, sweetness, and farmers’ preference for recommendation to producers.