Taxonomic Implication of Morphology of Seven Va-rieties of Vigna unguiculata (.L.) Walp. Cultivated in Awka Anambra State, South Eastern NigeriaBibian O Aziagba 1,*, C U Okeke 1, Chinelo A Ezeabara 1, Chinyere V Ilodibia 1,*, Toochukwu P Egboka 1, Ifeanyi Obika 2

1 Department of Botany, Nnamdi Azikiwe University, Awka, Nigeria2 Department of Zoology, Nnamdi Azikiwe University, Awka, Nigeria

* Corresponding author: Bibian O Aziagba, Department of Botany, Nnamdi Aziki-we University, Awka, Anambra State, Nigeria. E-mail: aziagbabibian@gmail.com; Chinyere V Ilodibia, Department of Botany, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria. E-mail: chinyereokafor206@yahoo.com

AbstractMorphological studies were carried out on the leaf, stem, petiole, petioluse, pod and seed of seven varieties of Vigna unguiculata (L.)Walp using standard methods. Similarities were observed in the habit, stem type, colour, leaf arrangement and type of leaf. Differences were observed in the leaf area (cm2), petiololuse length, petiole, stem length, pod weigth and seed colours. Iron beans showed the highest leaf area (82.85 cm2) while Oloka beans showed the lowest (21.75 cm2). Petioluse length was highest in crowther peas and potiskum while Oloka showed the lowest length (0.37 cm). Petiole length of Iron beans showed the highest (2.20 cm) while Oloka showed the shortest length (1.49 cm). Iron beans and potiskum showed the highest stem length (10 cm) and Oloka showed the lowest (7.67 cm). Pod weight of Ifebrown was highest (3.95 g) and Kafanji has the lowest weight (1.36 g). Pod length, number of pods per variety, seed colour, number of days to 50% flowering and maturity and number of branches were significantly different among the varieties. Carnonical discriminant function carried out on the plot based on morphological features showed kafanji, oloka and sokoto guzo to be in one cluster (1) indicating similarity in their morphological features and potiskum, iron beans, crowther peas and ifebrown in one cluster (2). The overall data showed significant differences in the phenotypic characteristics of the seven varieties, while similarities in and between the varieties showed close affinity and were more consistent in the genus Vigna.

© 2016. American Journal of Life Science Researches.

Submited: 06.12.2016Accepted: 09.20.2016

Keywords:Vigna unguiculataMorphological CharactersCarnonical Discriminant Function

American Journal of Life Science Researches

Oct2016, Volume 4, Issue 4

Original Article

DOI: 10.21859/ajlsr-040404

INTRODUCTION

The genus Vigna, formerly Leguminosae, (peas or beans) is composed of more than 200 species that are native to the warm regions of both the old world and new world. It is one of the several species of the widely cultivated Vigna; belonging to the kingdom plantae, family Fabaceae called papillionaceae and sub-family, Fabiodeae. Vigna unguiculata a species of Vi-gna is an annual dicotyledonous legume and a warm weather crop well adapted to drier regions of the tropics like Nigeria where other food legumes do not thrive well [1]. Nigeria is the largest producer and consumer, accounting for about 45 percent of its world‘s production [2, 3] while Africa accounts for about 75% [4, 5]. Classified cowpea varieties into size cat-egories based on their 100-seed weight. Varieties with seeds 10-15 g are described as small, 15.1-20 g as medium-sized seeds while large seeds have 20.1-25.0 g. Seeds weighing over 25 g are described as very large seeds. These varieties of cowpea vary greatly morphologically in their growth habits, which range from indeterminate to fairly determinate with the non-vining types tending to be more determinate. Seed

colour, from white, cream, yellow, and red, purple, brown to black and may be smooth or wrinkled according to [6]. These seeds differ in all physical properties which include hi-lum colour and seed coat texture. Seed shapes vary from the typical kidney shape for beans to globose, ovoid and rhom-boid shapes [5, 7] reported that morphological variability in cowpea (Vigna unguiculata (L.) Walp) abounds in the trop-ics. Poor concern for available but unutilized cowpea variants may promote the losses of diversity in the species. Condi-tions and grower preferences for each variety vary from re-gion to region [8]. Morphological characters of plants are commonly used in the description of varietal differences in leaves. Leaves vary greatly from plant to plant and are useful in classification and identification. Leaf appearance in crop plants is an important process involved in canopy develop-ment. There is also wide range among the plant genotypes in shape, size and number of leaves produced by plants. In cowpea, the leaf shape is important for taxonomic classifica-tion and also for distinguishing cowpea varieties. However,

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there isn’t a central naming convention for neither cowpea leaves nor detailed descriptions of the leaf shapes; thus, many researchers name the leaf shapes differently. The hastate leaf shape was reported to be dominant to the ovate leaf shape in several studies [9]. This may indicate that the hastate shape is ancestral to the ovate leaf shape and the preponderance of the latter in most cultivated cowpea is due to direct or indi-rect selection by humans over time. The loss of genetic di-versity, in part is due to the conventional breeding programs associated with modern agricultural practices, thus has been dramatic for many cultivated species [10]. Morphology aids in the classification of plants, this is as well as cytology, phy-tochemical and anatomy. Morphological data of plants are easily observable and obtainable and thus are used frequently in plant identification [11]. The external morphological evi-dence provides the basic language for plant characterization, identification, classification and relationships [11, 12], noted morphological characters as vegetative, phonological floral characters, seeds and fruit morphology thus morphological features of plants are those external diagnostic features of plants [13]. The objective of the study was to evaluate the significance of morphology in the seven varieties of Vigna un-guiculata and its implication in the classification of the plant.

METHODS

Source of Materials

The stems, leaves, petioles, roots and pods of the seven vari-eties of Vigna unguiculata were collected from the Botanical garden of Nnamdi Azikiwe University, Awka. These varieties were authenticated by plant taxonomists Prof. C.U. Okeke and Aziagba, Bibian and the specimen voucher deposited at the Herbarium in the Department of Botany.

Morphology Studies

The vegetative studies of the stems, leaves, petioles, petioluse and roots of Vigna unguiculata were carried out by visual obser-vations and use of hand lens. Leaf morphology (leaf length, leaf area, venation, margin leaf colour, and width), stem morphol-ogy (length, colour) seed morphology and pods weight was studied using metre rule and weighing balance.

Statistical Analysis

Results were presented in mean ± standard deviation and were subjected to analysis of variance (ANOVA) using Dun-can’s Multiple Range Test (DMRT) at 5% probability to sep-arate the treatments. Differences in mean value were consid-ered significant at P < 0.05

RESULTS

The result of this research revealed some similarities and differ-ences in the morphological characteristics among the varieties (Table 1). Similarities were observed in the habit, stem type, colour, leaf arrangement, apices, leaf type and shape. Differ-ences were observed in the leaf area; iron bean has the highest (82.85 cm2) and least was Oloka (21.75 cm2), (Table 1, Fig 2). Petioluse length was highest in Black beans (crowther peas) (0.60 cm) and lowest in Oloka (0.37 cm) (Table 1, Fig 3). Pet-iole length was highest in iron beans (2.20 cm) and lowest in Oloka (1.47 cm) (Table 1, Fig 4). Stem length was highest in crowther peas and Potiskum (10.00 cm each) (Table 1, Fig 5) and pod weight had significant differences recorded in gram with Ifebrown having the highest (3.93 g) while Kafanji had the lowest (1.36 g) (Table 1, Fig 6). Morphological Discrimi-nant functions for same morphological features showed signif-icant differences between the varieties (Fig 7).

Table 1: The Morphological Results of the Seven Varieties of Vigna Unguiculata (.L.) Walp. Are ShownIfebrown Potiskum Oloka Iron Beans Kafanji Sokoto Guzuo Crowther Peas

Habit Annual Annual Annual Annual Annual Annual AnnualStem type climbing/pros-

trateClimbing/pros-

trateClimbing/pros-

trateClimbing/pros-

trateClimbing/pros-

trateClimbing/pros-

trateClimbing/pros-

trateColour Green green Green green Green green GreenLeaf ar-rangement

alternate alternate Alternate alternate Alternate Alternate Alternate

Leaf Type Trifoliate trifoliate Trifoliate trifoliate Trifoliate Trifoliate TrifoliateLeaf length 7.5 ± 3.3 7.2 ± 3.6 5.0 ± 2.5 7.5 ± 3.3 10.8 ± 5.4 6.5 ± 3.3. 7.3 ± 3.7Leaf width 5.2 ± 2.6 5.1 ± 2.6 3.5 ± 1.8 5.5 ± 2.8 6.7 ± 3.4 4.2 ± 2.1 4.3 ± 2.2 Petiolelength

12.0 ± 6.0 8.5 ± 4.3 7.0 ± 3.5 12.2 ± 6.1 10.5 ± 5.2 10.2 ± 5.1 8.8 ± 4.4

Petioleouslength

2.5 ± 1.3 2.2 ± 1.1 1.8 ± 0.9 2.5 ± 1.3 0.5 ± 0.25 2.2 ± 1.1 2.3 ± 1.2

Leaf length 23.5 ± 11.8 23.5 ± 11.8 16 ± 8.0 22 ± 11 20.8 ± 10.4 20.2 ± 10.1 20.5 ± 10.3Leaf width 15 ± 7.5 14 ± 7.0 15 ± 7.5 16.2 ± 8.1 14.6 ± 7.3 14.2 ± 7.1 13.5 ± 6.8Leaf shape Sub-globose Sub-globose Sub-globose Sub-globose Sub-globose Sub-globose Sub-globoseVenation Arcuate Arcuate Arcuate Arcuate Arcuate Arcuate ArcuateLeaf mar-gin

Entire Entire Entire Entire Entire Entire Entire

Leaf apices Acuminate Acuminate Acuminate Acuminate Acuminate Acuminate Acuminate

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Figure 1: Vigna unguiculata in its Natural Habitat

Figure 2: Showing the Leaf Area (cm2) of Seven Varieties of Beans. The leaf area of iron beans was the highest (82.85) while that of Olo-ka was the lowest (21.75). Analysis of variance showed a significant difference in the leaf area between cowpea variety (P < 0.05).

Figure 3: Showing the Length of Petioluse (cm) of Seven Varieties of Beans. Crowther peas/ Black beans and potiskum showed highest length of petioluse (0.6 cm) while Oloka showed the shortest length of petioluse (0.37). Analysis of variance showed a significant differ-ence in the length of petiolouse between cowpea variety (P < 0.05).

Figure 4: Showing the Petiole Length (cm) of Seven Varieties of Beans. Iron beans showed highest length of petiole (2.20 cm) while Oloka showed the shortest length of petioles (1.47 cm). Analysis of variance showed a significant difference in the length of petiole between beans variety (P < 0.05)

Figure 5: Showing the Stem Length (cm) of Seven Varieties of Beans. Iron beans and potiskum showed the highest stem length (10 cm) while Oloka showed the least stem length (7.67 cm). Analysis of variance showed a significant difference in the stem length be-tween beans variety (P < 0.05)

Figure 6: Showing the Pod Weight (g) of Seven Varieties of Cow-pea. Ifebrown showed the highest pod weight (3.93 g) while kafanji showed the lowest pod weight (1.36 g).

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Figure 7: Showing Canonical Discriminant Plot of the Seven Beans Variety Based on Their Morphological Features. Kafanji, Oloka and Sokoto guzo were grouped to one cluster indicating similarity in their morphological features while Postikum, iron beans, black beans and Ifebrown were grouped into a different cluster.

Figure 8: Pod of Vigna unguiculata

Figure 9: Pod of the Vigna unguiculata Varieties Showing Their Dif-ferent Colours

DISCUSSION

Vegetative and phenotypic morphology observed strengthens the intra and interspecific relation-ship in the taxa. High variability among cowpea geno-

types based on phenotypic characters has been reported by some authors [14, 15]. Specific variation which differentiates genotypes with respect to some phenotypic characters may have ensued from natural and environmental mutations of the phenotypic traits. Morphological plasticity as reported by [16], cited by [17], stated that the variation in the mor-phological characters of genotypes which are phenotypically similar is due to genetic differentiation especially in the pres-ence of varying conditions and parallel evolution.

CONFLICTS OF INTEREDST

Authors have declared that no competing interests exist.

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