In West Africa, moringa leaves are mixed with other vegetables to make sauce. The use of the fresh and dried leaves as staple foods is very common in Burkina Faso. Leaves contain high amounts of total phenols and proteins and are a good source of vitamins and minerals: perhaps more than any other tropical vegetable (Ferreira et al., 2008). Moringa is used in many African feeding programs to fight malnutrition and its associated diseases, including blindness (Mulh et al., 2011). Fragrant flowers of moringa are also used as a source of vegetables and bee forage; twigs with leaves as fodder; green leaves as mulch and solid wood as energy source (Smith and Eyzaguirre, 2007).

Moringa is cultivated in tropical and sub-tropical areas with annual rainfall varying from less than 100 to over 1500 mm and different soils types (Nouman et al., 2012). It has been introduced into gardening systems because of its versatility (Palada and Chang, 2003; Nduwayezu et al., 2007).

Although moringa is grown throughout numerous agro systems, no large-scale commercial plantings have been reported, possibly as a result of the limited scientific data that is currently available on the morphological characteristics that control its survival and productivity. Therefore, further insights into the morphological characteristics of this species are needed before recommending its large scale introduction to home gardens of smallholders’ growers (Scott and Sullivan, 2007). At present, data are not available to make reliable recommendations to garden landowners on the best seed sources and how the species might perform in various agroforestry systems. Therefore, the objective of this study was to evaluate the variations in morphological characteristics of the growth of M. oleifera at nursery stage for selection of seed sources suitable for plantation establishment under different geoclimatic environmental conditions.

Study site

The study was conducted at the women gardening center “Amicale des Forestières du Burkina Faso (AMIFOB)” located at Ouagadougou, Burkina Faso (12°7’32’’N, 01°40’24’’W). The rainfall is uni-modal with a mean annual rainfall of the last 15 years data from the nearest meteorological station in Ouagadougou, of 950 mm year^-1, with the mean potential evapotranspiration of 177 mm. month^-1 and the mean temperature of 29.2°C month^-1 (Figure 1a and b). Soils are sandy clay to clay-sandy ferruginous leached with very low nutrient content according to French soil classification (Pallo et al., 2009). The common natural vegetation found at Ouagadougou is described as semi-deciduous open woodland. Main genera include, Eucalyptus, Azadirachta, Mangifera, Vitellaria, Lannea, Piliostigma, Acacia., Ziziphus, Tamarindus and Combretum.

Seed sources, experimental design and establishment

The experiment included eleven Moringa oleifera provenances of Ouahigouya (P1), Ségou (P2), Centre National de Semences Forestières (CNSF) (P3), Ouagadougou (P4), Koudougou (P5), Fada N’Gourma (P6), Bobo Dioulasso (P7), Dano (P8), Gaoua (P9), Tamalé (P10) and Niangon-Lokoua (P11) (Table 1). These provenances were selected from four countries, Burkina Faso, Mali, Ghana, and Ivory Coast and four climate areas according to their agro-ecological characteristics (Sahelian, Sub Equatorial, South and North Sudan). Seeds were collected in 2014 in plantation farmland from at least 12 mother trees per provenance. The experimental design was a randomized complete block design (RCBD) with three replications, and each plot represented a provenance planted at 5 x 6 rows in a contiguous arrangement of 20 x 20 cm (Figure 2). Plot measured 10 x 1 m and contained 30 trees and the distances between blocks were 2 m. Seed samples were pretreated with water for 24 h and sown in June 1^st 2014. Weeding was done twice during the rainy season. The seedlings were grown without fertilizers and pesticide.

Morphological measurements

The morphological measurements were performed on two-week and two-month old M. oleifera. Twenty seedlings from each provenance per block were selected randomly and their heights were assessed from root collar up to the terminal shoot using a measuring tape. At the age of two months, 20 randomly selected plants from each provenance in each block were labeled for counting the total number of branches per plant and pinnae per leaf.

Dry matter production

After two months from germination, all trees were harvested for dry matter measurements using an analytical balance. Each was separated into aboveground biomass (leaves, buds and stems) and underground biomass (roots), and dried at 70°C for 48 h using an oven.

Data analysis

All statistical analysis were carried out using ANOVA performed with JMP® Pro 11.1.1 (SAS Institute, Cary, NC, USA). Normality and homoscedasticity were graphically verified on residual plots of the linear models (Quinn and Keough, 2002). When effects were significant, the Duncan test was used for multiple mean comparisons to detect the significant differences between the means. Statistical significance was fixed at 0.05. The correlation between the morphological characteristic variables and the geoclimatic data (altitude, longitude and average rainfall) of each provenance seed origin was assessed using scattered diagram to determine the linearity and the trend of the relationships.

The underground biomass dry weight of the provenances varied from 1.0 to 7.4 g. The provenance P9 had the highest underground biomass dry weight, which was not significantly different from that produced by P3, P4, P5 and P6. However, significant difference appeared when they were compared with P1, P2 P7, P8 and P10, which produced the smallest underground biomass dry weight (Table 2). The underground biomass: above-ground ratio of the provenances varied from 0.4 to 0.9, and the highest ratio was shown by P10, but it was only significantly different from that of P1 and P8 (Table 2). Provenance P9 was also superior in total dry weight, which was significantly greater than the total dry weights produced by P1, P2, P5, P7, P8, P10 and P11 (Table 2).

The significant differences in biomass production among the different parts of the provenances are consistent with the findings by Kundu and Tigerstedt (1998) in Azadirachta indica and Hardiyanto et al. (2004) in A. mangium. The good performance in above and underground biomass production of the provenances Gaoua (P9), Fada N’Gourma (P6), Ouagadougou (P4) and CNSF (P3) was attributed to its advantages in good growth in height, number of branches, pinnae and leaves at the study site.

The results of this study indicate the existence of strong variations in seedling morphological characteristics and biomass production among the studied provenances. The climatic conditions prevailing in the seeds origins had no effect on the seedling's morphology and biomass production. The absence of significant correlations between the wide range of provenances from diverse geoclimatic conditions and the morphological traits and biomass production of M. oleifera was attributed to the ability of the species to grow on a wide variety of climate and soil types.

The authors have not declared any conflict of interest.

The authors are very grateful to the support provided by the technician Zeba Abinatou from the Forestry Department of the Research Institute of Agriculture and Environment of Burkina Faso, Denis Walsh for the useful help in statistics and the members of women association (AMIFOB) for their tireless efforts in making this work a success.