Correlation and path coefficient analysis of polygenic traits of upland cotton genotypes grown in Zimbabwe

Cotton is a very important crop that consists of traits with different associationship due to genetic and environmental factors. In order to determine the degree of association between seed cotton yield and important traits, a study was done using an RCBD experiment with ten genotypes. Seed cotton yield, GOT, lint yield, boll weight, bolls per plant, seed weight, plant height, fibre length, elongation, fineness and strength data were collected and analysed. Genotypic and phenotypic correlation analysis was done in Meta R. Estimation of direct and indirect effects was done using path analysis in Microsoft Excel. Analysis of variance revealed significant differences for boll weight, seed weight, GOT and plant height. Seed cotton yield was correlated with lint yield (r = 0.71***), fibre elongation (r = 0.54***), bolls per plant (0.27***), seed weight (r = 0.22***), strength (r = 0.21***) and fineness (r = 0.13*) at genotypic level. Ginning outturn was correlated with lint yield (r = 0.70***), elongation (r = 0.60***) and strength (r = 0.50***). Boll weight was correlated with seed weight (r = 0.56***) whilst plant height was highly associated with fibre strength (r = 0.58***). The adjusted R Square (0.98), low standard error (0.12) and low residual effect (R = 0.01) in regression analysis indicated that variability of seed cotton yield was explained by the causal variables. Lint yield had the highest direct effect on seed cotton yield (r = 1.055). Traits that could be used for indirect selection were bolls per plant (r = 0.006), seed weight (0.022) and or plant height (0.012). Gin outturn (0.737) had the highest indirect contribution to seed cotton yield through lint yield, followed by strength (0.012) through plant height, seed weight (0.011) through boll weight, fibre fineness (0.010) through boll weight. It was therefore concluded that selection of high yielding cotton genotypes could emphasize more on lint yield, boll weights, plant height and bolls per plant for better-performing lines. Gin outturn and fibre strength could be used indirectly to improve seed cotton yield through other traits.