Variance components, correlation and path analyses in cowpea (Vigna unguiculata L., Walp)
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Date
2021
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Abstract
Cowpea as a low-input crop has a potential to significantly ameliorate poor nutrition and food insecurity in sub-Sahara Africa if problem of poor seed yield is addressed. Adequate information on the relationship between yield components and seed yield is, however, crucial for the development of better-quality varieties to improve farmers’ field yield. To this end, twelve cowpea accessions of different seed sizes and mixed pedigrees were evaluated for two years in field trials of three replications laid out in a randomized complete block design. Data collected on plant vigour indices, yield components and seed yield were analyzed for variance components, Pearson correlation coefficient and structural equation modeling for path analysis. The accessions exhibited significant variation for all yield components including seed yield. In addition, the variance estimates indicated that substantial variations recorded were mostly genetic with high heritability values. Earliness in flowering and pod maturity recorded highly significant correlations and direct effect with yield components and seed yield. Positive correlation between precocity and high yield could be exploited in the development of improved varieties with early maturity for the savannah ecology with a characteristic short wet season. Importantly, all seed yield components are significantly correlated with each other and to total seed yield. Pods per plant, however, recorded highest coefficient values (r = 0.85; P < 0.001; 1.38**) for both Pearson correlation and path analysis, respectively, suggesting its importance as a yield component with highest direct effect on seed yield and should be a core selection index in cowpea breeding. The effect of size-number trade-off accounts for the counterbalance of direct effects of seeds per pod/plant (number) and seed weight (size) in cowpea and should be determined on genotype and/or seed size basis during selection. Plant vigour characters had no direct contribution to seed yield