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The purpose of this study is to determine the morphological diversity and distribution of Garcinia kola Heckel (Clusiaceae) in two preferential agro- ecological growth areas in C?te d’Ivoire, for the sustainable management of the species. Ninety-four (94) trees of G. kola were sampled in Affery (south) and Biankouma (west) and characterized on the basis of 13 quantitative characteristics of the fruit, the general appearance of a plant, leaves and seeds. This study revealed the existence of very significant variability and differences within the trees sampled for most characteristics. Very strong correlations were found among the characteristics of the fruits. On the basis of these characteristics, it emerged that the fruits of the Biankouma area are larger than those of Affery. Ascending hierarchical classification (AHC) structured the trees into three distinct phenotypic groups based on the following discriminating characteristics: fruit height (Hfr), seed mass (Mgr), trunk diameter (Dm), leaf width (largF), Height of first branch (HtF) and width of the petiole (larP). These parameters can be used as a basis for selecting and maintaining the high variability of G. kola . Analysis of the geographical distribution of trees, based on the nearest neighbour model, revealed an aggregate distribution in both areas.

Garcinia kola Heckel (Clusiaceae), known as “petit kola” in Côte d’Ivoire, is one of the most important non-timber forest product (NTFP) generators. Indeed, seeds are sought for their stimulating effects, aphrodisiacs, bad cholesterol cleaners and liver protectors [

As a result, there is strong anthropogenic pressure on this species. In Côte d’Ivoire, Ahoussou et al. [

This study was carried out in two agro-ecological areas of Côte d’Ivoire for three years, from 2015 to 2018. One is in the west (Biankouma) and the other in the south (Affery). The choice of these areas was made after several prospecting studies with wholesale and field merchants. The surveys revealed that most of their supply of “petit kola” grains originated in these two areas. Biankouma is a department in the west of Côte d’Ivoire and is part of the Tonpki region. This locality is located 635 km from Abidjan between 7˚44'00'' North and 7˚37'00'' West. The villages in which the work was carried out are Kanta, Kabakouma and Blagouin. Like the entire region, our study area is characterized by mountainous relief, ferralitic and hydromorphic soils. During the year the temperature generally varies from 17˚C to 33˚C with an average of 24˚C. The rainfall varies between 1300 and 2400 mm per year and the vegetation consists mainly of humid forest. Cocoa, rubber and oil palm are the main agricultural export resources, including coffee from the region, which is very popular.

Affery, the second study area, is located in the south of Côte d’Ivoire in the department of Adzopé, 101 km from Abidjan between 6˚18'54'' North and 3˚57'37'' West. The villages in which the work was carried out are Daguikoi, Npokoi, Agbokia and Kossoa. They are located between 4 and 10 Km from Affery. Like the whole region, Affery is located in a humid tropical climate zone, of the Attiéen type. This climate gives it a relatively constant temperature which oscillates around 27.5˚C with four seasons of uneven lengths. The annual rainfall is 1300 mm on average. The town of Affery is characterised by the presence of many hills whose average altitude does not exceed 100 metres. They are separated by long valleys that look like precipices from which several marigots and rivers sometimes leave. The vegetation is dominated by tropical rainforest. This vegetation is composed of two types of forests: primary forest, which is similar to classified forests, and secondary forest, which merges with the vast expanses of fallow land resulting from shifting cultivation and intense logging. The soils are mixed, sandy-clayey and suitable for growing coffee, cocoa, rubber and oil palm. Humid hydromorphic soils suitable for the cultivation of plantain bananas, sweet bananas, rice, etc. are also found there.

Morphological characterization was conducted on 94 adult trees in all two study areas. These trees have produced fruit at least once. They are considered as adults and therefore make it possible to record all the parameters of the study. These trees were monitored throughout their breeding season, from flowering to fruit harvesting, from April to November, to take into account all phenological stages. From the remarkable flowering stage to the next flowering stage for two cycles. 13 parameters were selected based on a work of Leakey et al. [

- Fruit parameters: Fruit height (HFr), fruit diameter (DiF), fruit mass (maF), pericarp thickness (EpP), seed box cavity (CLG), seed mass (Mgr), number of seeds per fruit (Ngr);

- The parameters of the shaft port: shaft diameter (Dm), height of the first fork (HtF);

- Leaf parameters: length (LgF) and width (largF) of the leaf, length (LgP) and width (largP) of the petiole.

On each tree, a minimum of thirty fruits were collected. Given the importance that owners attach to the tree, fruit is usually picked at the base of the trees. Thus, to ensure that the fruits are actually from the collected tree, the selected individuals are separated from each other by at least 25 m. All leaves were collected at the end of the first branch, from the ground, from all trees. Measurements were made on a minimum of thirty leaves per tree.

For data processing, EXCEL and R software were used. The means and analysis of variance made it possible to assess the difference between the parameters studied. The most discriminating variables and related species were identified. The statistical tools that are the PCA (Principal Component Analysis) and AHC (Ascending Hierarchical Classification) make it possible to achieve this objective. The classification carried out is a hierarchical bottom-up classification on the principal component and covers all the parameters studied. This classification was carried out according to the Ward method taking into account the Euclidean distance matrix. The relationships between the different parameters were studied on the basis of total correlations.

Transects were constructed and an inventory of Garcinia kola trees was carried out using GPS, in projected coordinate systems (x; y) and UTM (Universal Tranvers Mercator). It consisted in noting the geographical coordinates of each individual. Mobile sampling was conducted because the density per hectare of the tree is low; less than three trees per hectare on average. It consisted of walking through the environment in all directions, noting all the trees. This inventory made it possible to create a database.

Data analysis was performed using ArcGIS software. The Average Nearest Neighbor (ANN) tool was used to study the distribution [

The nearest average neighbor, Average Nearest Neighbor, is given by the following relationship:

A N N = D ¯ o D ¯ E

where D ¯ o is the average distance observed between each tree and its nearest neighbor

D ¯ o = ∑ i = 1 n d i n

And D ¯ E is the expected mean distance for the characteristics given in a random way

D ¯ E = 0.5 n / A

In the above equations, di is equal to the distance between entity i and the nearest neighbouring entity; n is the total number of individuals and A is the area of the minimum rectangle encompassing all entities, or an area value specified by the user

The z-score of the nearest average neighbour for the statistics is calculated as follows:

S E = 0.26136 n 2 / A

Tables 1-3 present the mean values of the fruit parameters and the result of the analysis of variance (ANOVA) for all trees sampled respectively within the population and between the two sites.

The variables fruit height Hfr and fruit mass maF show a significant difference for all trees in the two sites (

Parameters | Min | Max | Average | Standard deviation | CV (%) | F |
---|---|---|---|---|---|---|

HFr (mm) | 3.68 | 106.00 | 68.36 | 14.37 | 21.03 | ** |

maF (g) | 5.00 | 625.00 | 206.32 | 128.21 | 62.14 | ** |

DiF (mm) | 36.1 | 88.94 | 67.51 | 10.36 | 15.35 | ** |

EpP (mm) | 7.21 | 37.16 | 20.05 | 5.35 | 26.72 | ** |

CLG (mm) | 25.93 | 64.00 | 47.46 | 8.57 | 18.06 | ** |

Mgr (g) | 2.80 | 85.81 | 9.34 | 8.41 | 90.06 | ** |

Ngr | 1.00 | 4.00 | 2.08 | 0.89 | 43.01 | NS |

**: significant at the 5% threshold; NS: not significant at the 5% level. NB: Hfr: height of the fruit; maF: mass of the fruit; DiF: diameter of the fruit; CLG: cavity of the seed box; Mgr: mass of seeds; Ngr: number of seeds per fruit; EpP: thickness of the pericarp, CV: coefficient of variation.

Parameters | Min | Max | Average | Standard deviation | CV (%) | F |
---|---|---|---|---|---|---|

Dm (cm) | 15.28 | 76.43 | 44.91 | 12.75 | 28.39 | ** |

HtF (m) | 1.13 | 14.00 | 5.27 | 2.64 | 50.24 | ** |

LgF (cm) | 6.81 | 17.42 | 11.84 | 2.35 | 19.89 | ** |

largF (cm) | 2.43 | 15.86 | 5.04 | 1.71 | 33.92 | ** |

LgP (cm) | 0.78 | 3.70 | 1.38 | 0.34 | 24.70 | NS |

larP (cm) | 0.16 | 0.59 | 0.22 | 0.06 | 26.50 | ** |

**: significant difference at the 5% level; NS: not significant at the 5% level. NB: Dm: diameter of the trunk; HtF: height of the first branch; LgF: leaf length; largF: leaf width; LgP: petiole length; lgP: width of the petiole.

AFFERY | BIANKOUMA | ||||
---|---|---|---|---|---|

Variables | Average | CV(%) | Average | CV % | P |

Dm (cm) | 48.56 | 25.35 | 38.76 | 28.75 | 0.07 |

HtF (m) | 5.92 | 46.37 | 4.16 | 49.79 | 0.11 |

LgF (cm) | 11.22 | 20.15 | 12.90 | 16.70 | 0.04 |

largF (cm) | 4.60 | 24.50 | 5.79 | 38.28 | 0.07 |

LgP (cm) | 1.34 | 15.95 | 1.45 | 33.12 | 0.03 |

larP (cm) | 0.22 | 27.70 | 0.24 | 23.56 | 0.04 |

HFr (mm) | 65.17 | 20.00 | 73.75 | 20.48 | 0.04 |

maF (g) | 146.18 | 62.74 | 307.71 | 38.12 | 0.22 |

DiF (mm) | 64.61 | 16.01 | 72.41 | 11.75 | 0.04 |

EpP (mm) | 19.12 | 29.23 | 21.63 | 21.29 | 0.04 |

CLG (mm) | 45.50 | 18.67 | 50.78 | 15.24 | 0.04 |

Mgr (g) | 9.20 | 113.87 | 9.62 | 28.01 | 0.02 |

Ngr | 2.03 | 40.50 | 2.17 | 46.75 | 0.02 |

NB: The underlined probability values are not significant at the 5% level.

The diameter of the fruit DiF and the thickness of the pericarp EpP are significantly different at the 5% threshold for all trees and between sites (

The results of the analysis of variance indicate that there is a significant difference in the seed housing cavity between fruits from the same area and between areas (

The mass character of the seeds (Mgr) differs significantly between sites and within the entire sample (

Analysis of the variance analysis of the number of seeds per fruit (Ngr) for all trees shows that there are no significant differences (

For the trunk diameter characteristic measured at 1.30 m from the ground, the analysis of variance shows that there is a significant difference for the entire sample (

The height of the first branch varies from 1.13 to 14 m with an average of 5.27 m and a high coefficient of variation of 50.24%. The results of the analysis of variance (

The analysis of variance (

The data in

Correlations between parameters

The correlation matrix between the parameters studied (

Variables | Dm | HtF | LgF | largF | LgP | larP | HFr | maF | DiF | EpP | CLG | Mgr | Ngr |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Dm | 1 | ||||||||||||

HtF | 0.04 | 1 | |||||||||||

LgF | −0.23 | −0.08** | 1 | ||||||||||

largF | −0.04 | −0.08 | 0.57**** | 1 | |||||||||

LgP | −0.06 | −0,05* | 0.30** | 0.27** | 1 | ||||||||

larP | −0.14 | −0.16* | 0.35*** | 0.33** | 0.07 | 1 | |||||||

HFr | −0.02 | −0.13* | 0.22* | 0.27** | 0.06 | 0.27** | 1 | ||||||

maF | −0.07 | −0.15 | 0.29** | 0.25* | 0.13 | 0.13 | 0.50**** | 1 | |||||

DiF | −0.03 | −0.14 | 0.25* | 0.25* | 0.09 | 0.14 | 0.55**** | 0.74**** | 1 | ||||

EpP | 0.03 | −0.08* | 0.19 | 0.23* | 0.10 | 0.01 | 0.39*** | 0.39*** | 0.56**** | 1 | |||

CLG | −0.05 | −0.12 | 0.19 | 0.16 | 0.05 | 0.17 | 0.42**** | 0.65**** | 0.86**** | 0.06 | 1 | ||

Mgr | −0.01 | 0.04 | 0.01 | 0.08 | 0.04 | 0.01 | 0.03 | 0.05 | 0.09 | 0.03 | 0.09 | 1 | |

Ngr | −0.11 | −0.16 | 0.01 | −0.09 | −0.08 | 0.03 | 0.07 | 0.30 | 0.34 | 0.06 | 0.38 | 0.06 | 1 |

NB: Underlined values indicate variables between which there is a strong correlation, p < 0.0001 “****”, p < 0.001 “***”, p < 0.01 “**”, p < 0.05 “*”, r value without “*” are not significative.

- Diameter of the fruit (DiF) and the mass of the fruit (maF), with a correlation coefficient r = 0.74 and p value < 0.0001;

- Seed compartment cavity (CLG) and fruit mass (maF) with a correlation coefficient r = 0.65 and p value < 0.0001;

- Diameter of the fruit (DiF) and the cavity of the seed box (CLG) with a correlation coefficient r = 0.86 and p value < 0.0001;

- Fruit diameter (DiF) and pericarp thickness (EpP) with a correlation coefficient r = 0.56 and p value < 0.0001;

- Diameter of the fruit (DiF) and height of the fruit (HFr) with a correlation coefficient r = 0.55 p value < 0.0001;

- Fruit height (HFr) and fruit mass (maF) with a correlation coefficient r = 0.50 p value < 0.0001;

- Fruit height (HFr) and cavity of seed box (CLG) with a correlation coefficient r = 0.42 and p value < 0.0001.

The only correlation between the morphological parameters of the leaves is that between the width (largF) and length (LgF) of the leaf with a correlation coefficient r = 0.57 with p < 0.0001. No significant correlations are established between tree parameters, fruit parameters, seed parameters and leaf parameters.

Principal Component Analysis (PCA)

The principal component analysis (PCA) covers 08 parameters. Indeed, given the correlations between the parameters, 5 variables were eliminated to avoid redundancy.

The first two components explain most of the variability revealed by the quantitative variables studied. The two principal axes express 38.34% of the total variation.

The study of phylogenetic relationships between trees was carried out by means of ascendant hierarchical classification (AHC). The principle of AHC is to group together individuals that have a sufficient degree of similarity in the same set. The dendrogram resulting from the ascendant hierarchical classification (AHC) obtained by Ward’s method allowed the identification of two large sets (A and B) with 25 and 69 trees respectively. These sets are composed of trees from both populations. A truncation at resemblance level 50 gives a finer classification with three groups (I, II and III). Group I is identified with set A and groups II and III are included in set B (

Variables | Axis 1 | Axis 2 | Axis 3 |
---|---|---|---|

Dm | 0.27 | −0.55 | −0.12 |

HtF | −0.56 | 0.06 | 0.31 |

largF | 0.70 | 0.25 | 0.10 |

LgP | 0.42 | 0.51 | −0.22 |

larP | 0.64 | −0.23 | 0.20 |

DiF | 0.62 | −0.12 | 0.05 |

Mgr | 0.08 | 0.28 | 0.84 |

Ngr | −0.01 | 0.66 | −0.28 |

Eigenvalues | 1.89 | 1.25 | 1.02 |

% Expressed variance | 23.56 | 15.59 | 12.80 |

% Cumulative variance | 23.56 | 39.16 | 51.95 |

NB: The underlined values indicate the variables that contribute the most to the formation of the axes.

Groups | Staff | Trees | |
---|---|---|---|

I | 25 | A1; A26; A33; A40; A42; A48; A51; A54; A66; A68; A82; A84; A86; A91; A103; A110; BK25; BK27; BK29; BK41; BK44; BK52; BK58; BK59; BK71 | |

II | 23 | A5; A8; A12; A16; A22; A27; A34; A35; A36; A41; A43; A45; A50; A78; A99; A106; A108; A109; A111; A112; BK19; BK39; BK45 | |

III | 46 | A6; A10; A11; A13; A17; A28; A32; A37; A46; A65; A70; A74; A77; A79; A80; A83; A85; A93; A96; A101; A104; A105; A107; BK4; BK5; BK7; BK10; BK11; BK12; BK13; BK18; BK34; BK40; BK46; BK47; BK48; BK49; BK56; BK57; BK61; BK62; BK66; BK68; BK70; BK72; BK74 | |

Values in bold indicate the most representative trees in each group.

The differentiation between the three phenotypic groups resulting from AHC was refined by the analysis of variance to a classification criterion (ANOVA) of all the variables analysed. The results indicate significant differences (P < 0.05) for all variables except petiole length (LgP) and number of seeds per fruit (Ngr) (

Group I is characterised by trees with low average values for trunk diameter (34.65 cm) and fruit height (53.27 mm). Individuals in this group showed intermediate mean values for the height of the first branch (6.09 m), leaf width (widthF) and petiole width (0.21 mm). For this group, the seed mass is relatively high (7.14 g).

Group II had the highest mean values for trunk diameter (60.47 cm), height of first branch (6.09 m) and seed mass (8.17 g). No low mean values of the variables were recorded in this group. However, relatively high values were recorded for leaf width (4.51 mm), petiole width (0.20 mm) and fruit height (67.69 mm).

In Group III, leaf width (5.55 mm), petiole width (0.24 mm) and fruit height (76.90 mm) were the variables with the highest average values. On the other hand, seed mass recorded a low average value (4.49 g). For the individuals in this group, the height of the first branch is relatively high (4.56 m).

Variables | Group I (N = 25) | Group II (N = 23) | Group III (N = 46) | F | P | |
---|---|---|---|---|---|---|

Trunk diameter (Dm) cm | 34.65 ± 9.53^{c} | 60.47 ± 6.29^{a} | 42.17 ± 9.44^{b} | 51.92 | <0.001^{***} | |

Height of first branch (HtF) m | 6.09 ± 7.31^{ab} | 7.34 ± 3.08^{a} | 4.56 ± 2.23^{b} | 3.32 | 0.041* | |

Sheet width (largF) mm | 4.59 ± 1.09^{ab} | 4.51 ± 0.95^{b} | 5.55 ± 2.11^{a} | 4.34 | 0.016* | |

Petiole length (LgP) mm | 1.36 ± 0.23^{a} | 1.30 ± 0.19^{a} | 1.43 ± 0.43^{a} | 1.20 | 0.306^{ns} | |

Width of the petiole (larP) mm | 0.21 ± 0.04^{ab} | 0.20 ± 0.03^{b} | 0.24 ± 0.07^{a} | 4.01 | 0.020 * | |

Fruit height (HFr) mm | 53.27 ± 15.25^{c} | 67.69 ± 6.26^{b} | 76.90 ± 9.10^{a} | 40.51 | <0.001^{***} | |

Seed mass (Mgr) g | 7.14 ± 2.57^{b} | 8.17 ± 2.99^{a} | 4.49 ± 2.24^{c} | 7.28 | <0.001^{***} | |

Number of seeds per fruit (Ngr) | 2.05 ± 0.89^{a} | 1.81 ± 0.66^{a} | 2.23 ± 0.98^{a} | 1.63 | 0.202^{ns} |

For each parameter, the means with the same letters are statistically identical to the threshold P<0.05, according to the ppds test; ns: not significant; ** and *** indicate highly significant and very highly significant respectively.

The analysis of the distribution of Garcinia kola Heckel trees in Affery is shown in

Site | DO (m) | DE (m) | ANN | z-score | p | Area (m^{2}) |
---|---|---|---|---|---|---|

Biankouma | 157.46 | 320.35 | 0.49 | −8.42 | 0.01 | 30,788,879.98 |

Affery | 84.28 | 333.91 | 0.25 | −14.79 | 0.01 | 47,720,769.21 |

DO: Distance observed; DE: Expected distance; P: probability; ANN: Average Nearest Neighbor.

This study was initiated as part of a program for the sustainable management of non-timber forest products other than timber. More specifically, it is a programme aimed at the domestication of the Garcinia kola (Heckel) species, which is widely exploited in Côte d’Ivoire for its therapeutic values. This study aimed to assess the morphological diversity of Garcinia kola H. (Clusiaceae) in two preferential agro-ecological areas for tree growth in Côte d’Ivoire.

All the characteristics studied revealed a significant difference between the individuals sampled at the two sites combined. There is great heterogeneity between Garcinia kola H trees. These results are similar to those of Bationo [

The study of intra-population variability revealed high variability for fruit diameter (DiF), fruit height (Hfr), leaf width (largF), fruit mass (maF), grain mass (Mgr) and number of grains per fruit (Ngr). The high coefficient of variation at Affery for fruit mass (maF) and grain mass (Mgr) indicates greater variability between fruits in the Affery area. However, in Biankouman, these two characters have larger average masses, which suggests larger fruits and seeds than in Affery. This could be explained by the fact that the trees of Garcinia kola Heckel in Biankouma are found in a much more preserved forest environment, in a forest that is difficult to access. The number of seeds per fruit (Ngr) on the scale of all samples does not show any significant difference. However, this characteristic makes it possible to make the difference on a smaller scale, in a study area. Some seeds are larger, egg-shaped and elongated; this is believed to be due either to the influence of the microclimate on seed formation or to the existence of several Garcinia species. Thus, the mass of seeds and the number of seeds, the mass of fruits and the number of seeds per fruit would make it possible to gather as many divergent individuals as possible within the natural populations of G. kola. These parameters were highlighted by Nafan [

The study of inter-population variability reveals a significant difference between most traits, except Dm, HtF, largF and maF. Thus, these four characteristics do not allow the study of diversity between populations. These results are similar in J. curcas [

According to the PCA, the highest variabilities in this study are recorded for grain mass (Mgr), number of grains per fruit (Ngr), leaf width (largF), petiole width (largP) and trunk diameter (Dm). Concerning fruits, similar results were obtained in Santalum austrocaledonicum (Santalaceae) [

The ascending hierarchical classification (AHC) revealed three groups of phenotypic diversity. Furthermore, the independent distribution of trees of different origins (Affery and Biankouma) in the three groups suggests that genetic diversity was not related to geographical origin. This result would indicate a phyletic link between the different trees. Six traits were the most relevant to differentiate the AHC derived groups. These were, according to their discriminatory power, trunk diameter, fruit height, seed mass, leaf width, petiole width and height of the first branch. Thus, these characteristics would make it possible to characterise Garciniakola in a large-scale study.

The study of the distribution of trees within the two populations (Affery and Biankouma) revealed an aggregate distribution of trees. The average distance observed between trees is smaller at Affery (84.28 m) than at Biankouma (157.46 m). These results are similar to those obtained in Strombosia sheffleria [

This work has enabled us to gather information on the level and structure of the morphological diversity of Garcinia kola Heckel in two agro-ecological zones in Côte d’Ivoire. The geographical distribution of the trees of the two populations revealed an aggregated structure. The evaluation of the morphological diversity of G. kola made it possible to highlight the most discriminating descriptors. Indeed, at the fruit level, it is the height of the fruit and the mass of the grains that are the most discriminating. At the foliar organ and tree level, it was the width of the leaves and trunk respectively that revealed greater variability in the trees. The ascending hierarchical classification (AHC) has given details on the approximation of trees by structuring them into three groups of phenotypic diversity. The differentiation of these groups is based on six most discriminating parameters. These can be classified according to their order of discriminating power. These are trunk diameter, fruit height, seed mass, leaf width, petiole width and height of the first branch. In this way, the representatives of the three groups can be used to set up a wood yard to bring together most of the diversity of G. kola in Côte d’Ivoire. But since morphological markers are subject to variations related to the tree growing environment, we intend to extend this study to molecular analysis. Microsatellite primers have been selected to conduct this step. The combined results will make it possible to propose a strategy for the sustainable conservation of the resource.

The authors thank the village populations and the landowners of the study areas without which no data would be obtained. Thank you also to the research college of Genetics Laboratory of Nangui Abrogoua University.

The authors declare no conflicts of interest regarding the publication of this paper.

Komenan, A.O., Koffi, K.K., Gbotto, A.A., Kone, M., Akaffou, D.S., Kouakou, K.L., Kouassi, K.I. and Zoro, B.A. (2019) Morphological Diversity and Distribution of Garcinia kola Heckel (Clusiaceae) in Two Agro-Ecological Areas of Côte d’Ivoire. American Journal of Plant Sciences, 10, 1871-1887. https://doi.org/10.4236/ajps.2019.1010132