Asian Journal of Research in Agriculture and Forestry 1(2): 1-12, 2018; Article no.AJRAF.41234
Morphological Variability of Detarium microcarpum Guill. & Perr. (Caesalpiniaceae) in Benin, West Africa Agbo Ignace Relique1,2*, Missihoun Antoine Abel1,2, Dagba Aladé Rollande1,2, Assogbadjo Ephrem Achille3 and Agbangla Clément1,2 1
Laboratoire de Génétique Moléculaire et d’Analyse des Génomes, Faculté des Sciences et Techniques, Université d’Abomey-Calavi, 01BP 526, Cotonou, Bénin. 2 Laboratoire de Génétique et des Biotechnologies, Université d’Abomey-Calavi, 01BP 526, Cotonou, Bénin. 3 Laboratoire d’Ecologie Appliquée, Facultés des Sciences Agronomiques, Université d’AbomeyCalavi, 01 BP 526 Cotonou, Bénin. Authors’ contributions This work was carried out in collaboration between all authors. Author AIR proposed the idea of research, carried out the field data collection, analysed and proposed the manuscript. Authors MAA and DAR read the protocol and improved the manuscript drafted. Authors AEA and AC validated the research project and significantly contributed to the manuscript. All authors have read and approved the final manuscript. Article Information DOI: 10.9734/AJRAF/2018/41234 Editor(s): (1) Cengiz Yucedag, Professor, Department of Landscape Architecture, Mehmet AkifErsoy University, Turkey. Reviewers: (1) Frane Strikić, University of Split, Croatia. (2) Tiga Neya, Kwame Nkrumah University of Science and Technology, Burkina Faso. Complete Peer review History: http://www.sciencedomain.org/review-history/24745
nd
Original Research Article
Received 2 February 2018 Accepted 8th May 2018 rd Published 23 May 2018
ABSTRACT Aims: The present study aims to evaluate the morphological diversity of Detarium microcarpum populations in Benin for the conservation purpose. Methodology: Twelve quantitative and two qualitative variables were used in the phenotypic diversity based on the phytodistrict and soils groups of 78 D. microcarpum trees sampled in six phytodistrict of Benin. In order to access the phenotypic variability of the trees, the morphological variables were subjected to ANOVA one-way. Hierarchical ascending classification was also performed to group D. microcarpum populations based on the degree of similarity. Results: Results showed that the leaves and fruits of D. microcarpum trees were highly polymorphic. The phytodistrict and soil group significantly influence the variability of the _____________________________________________________________________________________________________ *Corresponding author: E-mail:
[email protected];
Agbo et al.; AJRAF, 1(2): 1-12, 2018; Article no.AJRAF.41234
morphological descriptors used. Three morphotypes were obtained from D. microcarpum population used, with an important inter-groups variability for the descriptors. Conclusion: The phenotypic variability observed suggested a fairly large genetic diversity of Detarium microcarpum. Trees belonging to subpopulation I (trees from Bassila and North Borgou phytodistricts) had the best fruit characteristics and could be used for varietal selection in Benin.
Keywords: Morphological variability; Detarium microcarpum; phytodistrict; Benin; West Africa. step in the characterization of the trees is the determination of the most discriminated morphological descriptors [12,13]. In addition, the soil parameters related to morphological variability is also essential for successful conservation of a forest species. The morphological descriptors were largely related to the quality of the soil being used support for its growth [12]. The morphological variation between population provides information on the variability due to the environment of the species' range. This informs about the possibilities of genetic erosion according to the genetic variability. The present study aims mainly to evaluate the morphological diversity of Detarium microcarpum in Benin. Specifically, this involved: (i) describe the morphological variability of D. microcarpum; (ii) analyze the influence of the phytodistrict and soils groups on the morphological variability of D. microcarpum; (iii) characterize the different morphotypes of Detarium microcarpum in Benin.
1. INTRODUCTION Forest ecosystems are a key indicator for the well-being of the planet. They contribute to the preservation of all components of biological diversity, regulate the water cycle, soil conservation. Forests also sequester the carbon storage, ensure people's food security at local, regional and global levels [1]. Through nontimber forest products (NTFPs), ecosystems are an important source of income for the well-being of local populations [2]. Among plant species with great importance to local populations in subSaharan Africa, Detarium microcarpum Guill. & Perr. (Caesalpiniaceae) deserved a particular attention [3-5]. The species is used by human as food and livestock through the fruits, leaves and seeds. It is used in the traditional pharmacopoeia but also as good lumber and firewood. In Benin, the species is present in six phytodistricts (Zou, Bassila, South Borgou, North Borgou, Mekrou-Pendjari and Atacora chain) located in Sudanian and Sudano-Guinean climate zones [6]. Local people of Benin use it in food, traditional medicine, fodder, burning, crafts and medico-magic [5,7]. These utilities associated to the frequency of use make this species over-exploited and becomes extremely rare in some areas in Benin [7-9].
2. MATERIALS AND METHODS 2.1 Study Area The present study was carried out in Benin (West Africa between 1˚ and 3˚40'E and 06˚30' and 12˚30'N) in six phytodistricts (Bassila, North Borgou, South Borgou, Atacora chain, MekrouPendjari and Zou) selected based on the presence of natural stands of Detarium microcarpum (Fig. 1) [6]. These phytodistricts amount the Sudano-Guinean and Sudanian climatic zones are distinguished from each other by their climatic and biophysical conditions (Table 1) [14].
Given the major role that phytogenetic resources of D. microcarpum play for local communities and the threat to the survival of this species, it is urgent to develop the strategies of conservation to avoid the extinction of the species. Therefore, the conservation of a forest species requires knowledge of the morphological variability in order to differentiate individuals and to target interesting morphotypes [10,11]. Preview studies on morphological variability of D. microcarpum were carried out in Mali and showed a high variability associated to a strong interaction between the genotypes and the environment [12]. The status of the variability of the species is still unknown in Benin. The lack or absence of data makes efforts to identify the morphotypes of this forest species inefficient. The first important
2.2 Data Collection Seventy-eight (78) trees of D. microcarpum were prospected with thirteen (13) trees per phytodistrict spaced and spared to 50 meters at least. All individuals sampled in a phytodistrict were considered to be a population as well as those from the same soil group. Each tree has been recorded with Geographical Positioning System (GPS). 2
Agbo et al.; AJRAF, 1(2): 1-12,, 2018; Article no.AJRAF.41234 no.
Fig. 1. Geographic distribution of D. microcarpum in Benin [6] Twelve (12) quantitative and two (2) qualitative variables were measured on the trunk, leaves and fruits of species. The dendrometric variables used on each tree are: plant height (Hpl), trunk diameter (Dbh), crown height to the soil (Hpr) measured by a decameter, cameter, and color bark of the trunk (Cec) by a color chart (Royal Horticultural Society Color Chart). On each tree, 3 normal and non-parasitic parasitic leaves were identified and following
variables were measured: leaf length (Lfe), leaf width (lfe) measured by a decameter, leaf peduncle diameter (Dpf), leaflet length (Lfo), leaflet width (lfo) measured by a calipers, number of leaflets (Nfo) and leaf type (Tyf). On each selected tree, 5 fresh and ripe fruits were randomly chosen. The variables estimated were: fruitt length (Lfr), fruit width (lfr) measured by a calipers and the weight of fruit (mfr). 3
Agbo et al.; AJRAF, 1(2): 1-12, 2018; Article no.AJRAF.41234
Table 1. Biophysical characteristics of the phytodistricts surveyed Phytodistrict Bassila
Zou South Borgou North Borgou Atacora Chain
Climatic zone GuineoSudanian
Sudanian
MekrouPendjari
Rainfall regime Tendency to unimodal
Unimodal (1 rainy season)
Rainfall (mm) Min: 1100 Max: 1300
Types of soil (major) Ferrallitic soils with concretions and breastplates
Min: 1100 Max: 1200 Min: 1100 Max: 1200
Ferruginous soils on crystalline rocks Poorly evolved & mineral soils
Min: 900 Max: 1000
Ferruginous soils with concretions on sedimentary rocks
Major plant formation Semi-deciduous forest, woodland, and riparian forest Dry forest, woodland, and riparian forest Riparian forest, dry forest, and woodland Tree and Shrub savannahs, dry forest and riparian forest
D. microcarpum in Benin using Minitab_16 software [19].
2.3 Data Analysis The geographical coordinates of D. microcarpum trees have been projected on Harmonized World Soil Database v1.21 [15] where the corresponding soils groups were considered in this study.
3. RESULTS AND DISCUSSION 3.1 Results 3.1.1 Description of morphological variability of D. microcarpum
To describe the morphological variability of D. microcarpum, descriptive statistics (mean, standard deviation and variation coefficient) were performed on the morphological quantitative variables of the trees in all populations in order to evaluate inter and intra-population variability of the species. The test-T of Student-NewmanKeuls was performed to compare the means of each variables at the threshold of 5%. Principal components analysis of variance was performed on the morphological descriptors collected in the six sub-populations in order to analyze and share the global variability due to individuals, phytodistrict, and soils groups. Classification of the variability of the trees was performed based on phytodistricts and soils groups using the scale proposed by Ouédraogo et al. [16]. This scale was used successfully by Kouyaté et al. [17] and Sourou Kuiga [11], is as follows: (1) low variation (CV = 0 - 10%); (2) middle variation (CV = 10 15%); (3) high variation (CV = 15 - 44%); (4) significant variation (CV> 44%).
Tables 2 and 3 respectively showed the variations of twelve (12) quantitative descriptors of the leaves, fruits and dendrometric of D. microcarpum according phytodistricts and soils groups of the collection sites. 3.1.1.1 Trunk and crown The height of D. microcarpum tree varied from 3.10 to 12.30 m with an average of 6.42 (± 0.22) m and the height of crown from 1.01 to 3.60 m with an average of 2.08 (± 0.07) m. The trunk diameter varied from 20.50 to 129.00 cm with an average of 50.64 (± 2.27) cm. Within each phytodistrict, variability of height and trunk diameter of the trees was significantly (CV ≥ 44%) in south Borgou than in other phytodistricts (15%
