Character Association Studies in Groundnut (<i>Arachis hypogaea</i> L.)

Abstract

The aim of this study was to evaluate the degree of relationship and association amongst morphological characters of groundnut as an important food crop in Nigeria. 118 cultivars were planted in a completely randomized design structure. Characterization was based on qualitative and quantitative evaluations of 62 characters. Data w ere analysed on the SPSS software (20.0 versions). Correlation tools were applied using Spearman, Kendall and Pearson methods. Level of relationship was determined based on the strength of coefficients R. Dependence among traits was tested using the Chi square. Multiple regression analysis was carried out in a predictive model. As a result, many of the traits are very weakly correlated. Day to emergence has no effect on Day to 50% flowering (R = 0.237, <i> p </i> < 0.05) and number of flower (R = 0.221, <i> p </i> < 0.05). Day to first flowering weakly correlates with maturity time of the plant (R = 0.39, <i> p </i> < 0.01) but no effect on the yield. Also, number of flower correlates moderately with number of pods (R = 0.535, <i> p </i> < 0.01) and seeds (R = 0.409, <i> p </i> < 0.01). Plant height also moderately affects leaflet sizes (R = 0.354, <i> p </i> < 0.01) with a low R 2 of 13%. Plant biomass moderately affects number of pod (R = 0.494, <i> p </i> < 0.01), pod length (R = 0.395, <i> p </i> < 0.01), pod width (R = 0.473, <i> p </i> < 0.05), number of seed (R = 0.468, <i> p </i> < 0.01) and seed weight (R = 0.548, <i> p </i> < 0.01). Most of the high positive correlations recorded (R > 0.6 , <i> p</i> < 0.9) were observed amongst pod and seed parameters. Pod sizes significantly affect the number of seeds present (R = 0.551, <i> p </i> < 0.01) with R 2 of 30%. Qualitative traits have no effect on each other as all coefficients are very low. Pod constriction and sizes have no relationship (R = - 0.029). Tolerance to diseases is not affected by any qualitative trait. Also, no trait determines seed colour. Pubescence of young and mature leaflets recorded the only high positive correlation among all qualitative traits (R = 0.837, <i> p </i> = 0.01). However, leaf and stem pubescence have no relationship. The following traits significantly depend on cultivar type: disease tolerance ( <i> χ </i> 2 = 17.93, <i> p </i> = 0.000), plant survivorship ( <i> χ </i> 2 = 39.97, <i> p </i> = 0.000) and pod yield ( <i> χ </i> 2 = 69.695, <i> p </i> = 0.008). Seed yield has been predicted in a fit model with R 2 of 51% and significant <i> p </i> values ( <i> p </i> < 0.05) among some predictors. When appropriately applied, the information provided in this report may be useful to groundnut growers and breeders as well those interested in systematic studies of the crop.