Towards a domestication strategy for indigenous fruit trees in the tropics

[Extract] Increasingly, agroforestry trees are being improved in quality and productivity through the processes of market-driven domestication {Simons, 1996; Simons and Leakey, 2004; Leakey et al., 2005d}, based on strategies which consider: (i) the needs of the farmers, their priorities for domestication (Maghembe et al.,1998; Franzel et al., Chapter 1, this volume) and an inventory of the natural resource {Shackleton et al., 2003a}; (ii) the sustainable production of agroforestry tree products, including fruits, nuts, medicinals and nutriceuticals,timber, etc.; (iii) the restoration of degraded land and reduction of deforestation; and (IV) the wise use and conservation of genetic resources. These approaches to tree domestication are being implemented in southern Africa (Akinnifesi et al., 2006)

On-farm evaluation of soybean and cassava intercropping in south-west Nigeria

Farmer-participatory and researcher-managed trials were conducted at Ayepe, in south-west Nigeria, between July, 1991 and October, 1992, to determine the biophysical compatibility of soybean and cassava intercrop and the optimum time for introducing cassava (Manihot esculenta Crantz) in soybean-based intercropping systems. Soybean (Glycine max L.) was planted in monoculture and also intercropped with cassava at varying stages of soybean development. Results indicated that seed yield of soybean was depressed by intercropping. Land equivalent ratio (LER) increased with growth stage of soybean prior to introduction of the cassava intercrop. Yield of soybean ranged from 327 kg ha-1 to 642 kg ha-1 in farmers' fields, and from 723 kg ha-1 to 1201 kg -1 in the researcher managed field. Intercropping caused slight etiolation during the early growth of cassava but this disappeared after soybean harvest. Tuberous root yield of cassava was improved by intercropping irrespective of the stage of development of soybean. Relative total yield increased with growth stage of soybean prior to introduction of cassava. Both crops were least competitive with each other when intercropped at 6 weeks after sowing soybean. Introducing cassava into soybean in a relay-intercropping system is advantageous for this agroecological zone.Des essais en collaboration avec des fermiers et geres par des chercheurs ont ete menee entre juillet 1991 et octobre 1992 e eyepe (sud-est du Nigeria) afin de dAterminer la compatibilite biophysique du soya et du manioc pour la culture intercalaire et le temps optimal pour introduire le manioc (Manhiot esculenta Crantz) dans un systeme intercalaire e base de soya. Le soya (Glycine max L.) etait plante en monoculture ainsi qu'en culture intercalaire avec manioc e des stades variables du soya. Les resultats indiquaient que le rendement du soya est diminue par la culture intercalaire. La proportion d'equivalence de terre (LER) augmente avec le stade de developpement du soya au moment de l'introduction de la culture intercalaire. Le rendement de soya variait de 327 kg par ha jusque 642/ha sur les champs des fermiers, et de 723 jusque 1201 sur les champs geres par les chercheurs. La culture intercalaire causait un etiolement pendant la croissance initiale du manioc, mais ceci disparait apres la recolte du soya. Le rendement des racines tubereuses de manioc augmentait en culture intercalaire et ceci etait independant du stade de developpement du soya. Le rendement relatif total augmentait avec le stade de developpement du soya avant l'introduction du manioc. La concurrence entre les deux cultures atteignait son niveau le plus bas quand l'intercalation se faisait 6 semaines apres le semis de soya. L'introduction du manioc en intercalation avec la culture du soya est avantageuse dans cette zone agroecologique

Spatial rooting patterns of gliricidia, pigeon pea and maize intercrops and effect on profile soil N and P distribution in southern Malawi

The concept of competition or complementarity between tree and crop roots for below ground resources have been a major debate in simultaneous systems. Root studies were conducted in three cropping systems, namely: sole maize, pigeon pea/maize intercropping and Gliricidia sepium (Gliricidia)/maize intercropping, with the objective of understanding the potential for competition or otherwise. Pigeon pea and maize root development was monitored at 21, 42 and 63 days after planting (DAP). Also soil mineral N and Olsen P were assessed along the soil profile up to 200 cm depth. Maize roots developed faster than those of pigeon pea during the first 42 days after planting and there was little overlapping of maize and pigeon pea roots. However, the roots of both pigeon pea and maize had its peaks at 63 DAP, suggesting potential competition during reproductive growth stage of maize. In Gliricidia/maize intercropping, maize had the highest root density averaging 1.02 cm cm(-3) in the top 0 -4 0 cm soil layer, whereas gliricidia had lower root length density (0.38 cm cm(-3)) in the top 0 - 40 cm soil layer compared to 0.65 cm cm(-3) in the subsoil (40 - 100 cm). In Gliricidia/maize intercropping, mineral N was increased by 34 - 44 kg ha(-1) in the 0 - 100 cm soil layer, whereas Olsen P decreased by 32 kg ha(-1) in the entire 0-200 cm soil profile compared to the sole maize plot. Pigeon pea may be the "loser" in an association that involved both maize and Gliricidia. Because maize had more roots growing within 0 40 cm soil layer than Gliricidia it is able to take advantage of the nutrients from the applied Gliricidia prunings in the ridges. The study confirmed root compatibility between Gliricidia and maize and nutrient pumping from deep soil layers

Effect of agroforestry woody species on earthwarm activities and physicochemical properties of warm casts

The effects of five agroforestry woody species (Dactyladenia barteri, Gliricidia sepium, Leucaena leucocephala, Senna siamea andTreculia africana) on the surface aasting activity ofHyperiodrilus africanus were studied in an Alfisol (Oxic Paleustalf) in southwestern Nigeria. Casting activity under the woody species decreased in the following order:Dactyladenia sp. (26.4 Mg ha-1 year-1)>Gliricidia sp. (24.4 Mg ha-1 year-1)>Treculia sp. (22.9 Mg ha-1 year-1)>Leucaena sp. (18.6 Mg ha-1 year-1)>Senna sp. (18.3 Mg ha-1 year-1). These differences in casting activity were partly explained by microclimatic effects. Irrespective of the woody species, the worm casts were higher in clay and silt contents, bulk density, water-stable aggregates, pH, organic C, exchangeable cations, effective cation exchange capacity, and extractable P levels than the corresponding surface soils. The woody species did affect the physicochemical properties and P sorption of the worm casts. The content of water-stable aggregates of worm casts decreased in the following order:Dactyladenia sp.>Treculia sp.>Senna sp.>Leucaena sp.>Gliricidia sp. Large differences in extractable P levels were observed.Senna sp. was associated with the highest extractable P level (11.5 mg kg-1) andTreculia sp. the lowest (4.9 mg kg-1). P sorption was highest on worm casts underDactyladenia sp. and lowest on those underTreculia sp. Without fertilizer application, there were no significant differences in the dry weight of maize grown in the different worm casts. With NPK applications, the dry weight of maize grown in worm casts associated withTreculia sp. was significantly lower than that of maize grown in the other worm casts, mainly due to the low extractable P level. Despite a high organic C and exchangeable K status, maize grown in the worm casts still responded significantly to N and K applications. The N uptake by maize grown in worm casts associated withTreculia sp. was lower than that in the other treatments

Genetic variation among and within provenances of Adansonia digitata L. (Baobab) in seed germination and seedling growth from selected natural populations in Malawi

Baobab (Adansonia digitata L.) trees have a wide variety of subsistence and economic values across sub-Saharan Africa. Knowledge of the genetic variation within and between the species is essential for management and designing domestication, improvement and conservation strategies. Fifty-nine half-sib families were evaluated in the nursery to determine the genetic variation and control within and between the populations from four silvicultural zones. Seed germination and seven seedling growth parameters were assessed. Total phenotypic variance, family variance, within family variance, individual narrow sense heritability, and additive genetic coefficient of variation (AGCV) were derived from observed and expected mean squares. There were highly significant differences in seed germination, plant height, root collar diameter, number of leaves, shoot height and diameter, tuber diameter and weight. Provenance variation in germination ranged from 46.7 ± 3.3 to 68.7 ± 3.3% while tree-to-tree variation ranged from 6.3 ± 8.6 to 95.5 ± 8.6%. Coefficient of variation in seedling growth variables ranged from 18.6 to 43.6%. Individual narrow sense heritabilities (h 2) ranged from 0.07 to 0.71. AGCV ranged from 3.21 to 14.67%. Morphological traits showed that mainland populations were genetically distant from the island one. High and moderate additive genetic control of traits and AGCV show the potential that Baobab can also respond well to tree improvement. High phenotypic variation found in the study offers an opportunity to effect selection of superior attributes at both provenance and individual tree-to-tree level. © 2012 Springer Science+Business Media B.V

Phenotypic variation in fruit and seed morphology of Adansonia digitata L. (baobab) in five selected wild populations in Malawi

Adansoniadigitata L. (Baobab) is widely distributed throughout Sub-Saharan Africa stretching from Senegal to Sudan, and from Ethiopia to Natal. Information of phenotypic and genetic variation is a prerequisite for the domestication and improvement of baobab fruits from the wild. A study was done to determine within and between provenance variability in fruit and seed characteristics of five populations selected from four silvicultural zones and assess whether morphometric traits could delineate populations from different zones into land races. Fruits were characterized from 55 trees representing a wide geographical range. Six fruit traits and three individual seed traits were assessed. Results showed highly significant differences (P ≤ 0.001) in fruit, pulp, and seed weight, fruit length and width, number of seed, individual seed weight, seed length and width within and between populations. Mean fruit weight ranged from 125.8 ± 3.25 to 162.9 ± 3.25 g, seed weight ranged from 38.6 ± 2.5 to 66 ± 2.01 g and pulp weight ranged from 28.7 ± 1.33 to 41.4 ± 1.33 g. Single seed weight showed pronounced evidence of divergence of populations into ecotypes. The rich diversity found between and within populations is important for domestication purposes and tree improvement through selection and breeding. All populations could be used for seed source but distribution should be consciously done recognizing existence of races. © 2012 Springer Science+Business Media B.V

Performance of selected woody agroforestry species grown on an Alfisol and an Ultisol in the humid lowland of West Africa, and their effects on on soil properties

Performance of commonly grown agroforestry woody species was assessed at two locations in southern Nigeria, on an Alfisol (Oxic Paleustalf) at Ibadan in the forest-savanna transition zone and on an Ultisol (Typic Paleudult) at Onne in the forest zone, with annual rainfall of 1280 and 2400 mm respectively. The improvement effect of the wood species on soil properties appeared to be more pronounced on the Alfisol than on the acidic and nutrient poor Ultisol. Cordia alliodora and Gmelina arborea performed equally well on both sites, but Cardia alliodora seemed to be more suitable for use in an agroforestry system. Leucoma leucocephala and Pterocarpus soyauxii, which performed better on the Alfisol, were more suitable for use in agroforestry systems in this ecozone. Dialium guiñéense, Irvingia gabonensis, and Treculia africana had more potential for use in agroforestry systems on the Ultisol in the humid forest zone. Fruit productivity in these wild fruit species was found to differ between sites; substantial between-tree variations were observed. Indicative productivity values for future economic evaluations of Irvingia gabonensis plantations are presented

Pioneer woody species in Leucaena leucocephala and senna siamea hedgerows in a forest ecoysystem in southern Nigeria

Floral richness is an important feature of the tropical forest ecosystem. Large numbers of potentially useful volunteer species are usually present in crop fields in traditional farming systems. However; traditional farm lands are undergoing rapid deterioration as a result of increasing population pressure, with the resulting practice of continuous cultivation with little or no fallow. Consequently, many valuable woody species are at the verge of extinction. Work reported in the present study involved the phytosociology of pioneer woody species within hedgerows of Leucaena leucocephala. (Lam.) de Wit and Senna siamea (Irwin & Barnedy) from 16 dispersed farmer-managed alley cropped fields in southwestern Nigeria. The 31 different woody species encountered in the survey had 72.6% similarity coefficient between hedgerows of Leucaena and Senna. Effects of hedgerow species on microsite conditions, and inter-specific associations among volunteer species were discussed in the context of sustainability