Morphological Diversity and Cytological Studies in Some Accessions of Vigna vexillata (L.) A. Richard
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Aim: The objectives of this study were to characterize and evaluate intraspecific relationship among
twenty-six accessions of Vigna vexillata (L.) and work out interrelationship among the morphological
traits which could be used for genetic improvement of cowpea, V. unguiculata (L.) Walp.
Study Design: Field experiment was laid out in blocks of five buckets per accession in a row giving
a total of 260 plants.
Place and Duration of Study: At the experimental field of the Department of Biological Sciences,
Covenant University, Ota, Ogun state, Nigeria, during the dry planting season (September –
December, 2012). Methodology: A total of 26 traits comprising 18 quantitative and 8 qualitative traits of the
vegetative, floral, pod and seed were evaluated using descriptive statistics, Pearson Correlation
Coefficient (PCC), Principal Component Analysis (PCA) and Cluster Analysis (CA). Mitotic
chromosome counts and meiotic behaviour were studied using root tip cells and pollen mother cells
from young flower buds.
Results: The analysis of variance showed that all quantitative morphological characters were
significantly different among the accessions (P = 0.01) except stipule length and width. There were
significant correlations among characters such as calyx lobe length, standard petal length and width,
peduncle length, days to 50% flowering, days to 50% pod maturity, pod length and width, number of
locules per pod, number of seeds per pod, and 100-seed weight which could be used for breeding
and conservation purposes. The first six principal components accounted for 89.84% of the total
variance. The cluster analysis segregated the 26 accessions into three main clusters; cluster I (15
accessions), cluster II (10 accessions) and cluster III (1 accession). Mitotic chromosome counts of
2n = 22 were recorded for all the accessions and meiosis was observed to be normal with the
formation of eleven bivalents (n = 11).
Conclusion: The intraspecific variabilities indicates plasticity in the genomes of the studied
accessions, with high correlations among the morphological characters which are common to all
accessions, thus justifying their grouping as a species. The morphological and reproductive
attributes displayed by accessions TVnu93 and TVnu97 in terms of plant vigour, early flowering and
pod maturity, longer pods and relatively high 100-seed weight made them good potential candidates
in breeding for host plant resistance in cowpea.
Keywords
QH Natural history, QH301 Biology