SOURCE:

Faculty: Biosences
Department: Botany

CONTRIBUTORS:

Aziagba, B. O.
Okeke, C. U.
Okigbo, R. N.

ABSTRACT:

The genusVignabelongs to the family Fabaceae formerly Leguminosae.It is chiefly a vegetable and grain crop for human. Taxonomic Studies were carried out on seven varieties of Vignaunguiculata (L.) namely Ironbeans,Potiskum,Ifebrown,Sokotoguzo,Kafanji,Oloka and Crowderpeausing standard methods. Studies on the morphology of the seven varieties were carried out by selecting randomly the third and fourth fully opened leaves. Visual observation on the physical form and external structure was carried out on the plant. Measurement of the lengths of the leaves, stems, petioles, pods was carried out from the tip to the base.Anatomicalstudy on the transverse sections of the leaf, stem, petiole and root was done using microtome and free hand sectioning involving fixation of tissues. Cytological study was done with the roots of desired length (10mm) obtained at hourly interval of 8.00am -3.00pm and fixed in Carnoy’s fluid, the fresh root tips were mounted on a clean slide, stained with FLP Orcein and squashed with blunt end of a biro,Phytochemical and proximate compositions of seven varieties of this genus were done using standard gravimetric and spectrophotometric methods. Analysis of variance(ANOVA) was used to determine the level of significance and the result was presented as mean ± standard deviation. Morphological studies revealed similarities in the stem type,leaf shape, colour,apex,baseand type. Variations observed instem length, petiole length,pod weight, seed colour, seed texture, hilum colour, seed shape, leaf area and canonical discriminant function showed significant variability. Epidermal leaf studies revealed paracytic and anisocytic type of stomata at the abaxial and adaxial surface; the abaxial surface showed more stomata on the surface.Paracytic stomata were dominant in all the varieties except in’Ifebrown’that showedanisocytic at the abaxial surface. Macro and micro morphological studies obtained strengthened the intra and interspecific relationship in the genus. The result of the anatomical studies on the leaf, stem, root and petiole revealed the presence of epidermis, angular collenchyma, xylem and phloem alternating with each other, intercellular spaces,and pores of various sizes, apotrachial and paratrachial parenchyma and rays of various sizes.Var.’Oloka’ had ridges and furrows in the stem. Vessels in ‘Iron beans’ roots were in radial multiples while vessels in Crowderpea were round and exclusively solitary. Parenchyma in Crowderpea was broad and conspicuous. Unicellular trichomes were observed in petioles. Number of vascular bundles found in petioles was10-14 and in the stems 22-28. Similarities in the anatomy were stable while variations were non-significant. Mitotic chromosome was 2n= 22 at the early metaphase in Ironbean and ‘Sokotoguzo’ and late metaphase in ‘Oloka’ varieties; 2n= 24 at the telophase and prophase stage in Ifebrown, ‘Kafanji’, ‘Potiskum’ and Crowderpea varieties indicating polyploidy. ‘Kafanji’, ‘Oloka’ and ‘Sokotoguzo’ are more closely related taxonomically likewise ‘Potiskum’, Iron beans, Crowderpea and ‘Ifebrown’. The phytochemical results revealed the presence of alkaloid, flavonoid, tannin, saponin, steroid, phenol, phytic acid in various percentages, signifying its medicinal values. The highest phytochemical was alkaloids in the stem of ‘Ifebrown’(3.19±0.007%) and the highest proximate was dry matter in the stem of ‘Crowderpea’ (93.14±0.000%). Crude protein in the seed of ‘Oloka’ was highest (21.78±0.028%). ‘Oloka’ variety also showed highest composition of phytic acid (1.74±0.021%), trypsin (16.7±0.014%) starchyose (1.90±0.000%) and oxalate (2.74±0.021%). Based on these results, inter and intraspecific relationships were established in the characters signifying phylogenetic relationship while some variations may be as a result of hybrid breakdown in the genus or environmental conditions.This study therefore provided data that can be used to enhance proper taxonomic characterization, identification of Vigna speciesand justification of the use of these varieties in ethnomedicine. Additional information which might help in resolving issues in the taxonomy of Vignaunguiculata has also been provided hence the construction of a taxonomic key(dichotomous key) for the identification of varieties of Vignaunguiculata. A new nameVignabibianensiswas suggestedfor Crowderpea and Vignazigbanensis for Sokotoguzo which introduces a new species ‘specific epithet’ in Vigna. These data will assist in understanding this distinction and affinity which exist in and within these varieties under the genus Vigna.