Correlation, path-coefficient and genetic divergence for agro-morphological traits among coffee hybrids grown under coffee berry disease prone environments

Abstract

Knowledge of interrelationship among economic characters and genetic diversity helps plant breeders in outlying efficient breeding strategies for development of high yielding coffee cultivars. Eight selected coffee hybrids originally developed from crosses between Ethiopian Arabica coffee diversity and two commercial check varieties were tested for component associations and quantifying genetic divergence among genotypes at two sites in highland coffee growing agro-ecology of Southwestern Ethiopia during 2013/14 and 2014/15 cropping seasons. Data were collected for 14 agro-morphological traits. Combined ANOVA, Correlation, path and genetic divergence analyses were used to interpret the data. Significant genetic variation existed among the hybrids and check varieties in almost all traits. The genotypic correlations were higher than the phenotypic, indicating a prevailing influence of the genotypic over the environmental effects in the relationship between significant traits; the same sign indicates their tendencies to reinforce each other. Both the correlation and path coefficient analyses indicated that trait canopy diameter followed by length of primary branches and internodes length of primary branches appeared to be the first order traits for higher berry yield in Arabica coffee and priority should be given in selection due to strong associations as well as high magnitudes of direct effects on berry yield. Genetic distance estimates using the morphological traits showed moderately high genetic distance. Cluster analysis based on the distance measures grouped the ten genotypes in to three main clusters. The hybrid check variety Ababuna clustered alone in separate cluster, while the variety check 74110 and the hybrid HC1 clustered together. The other seven test hybrids also clustered together in shared sub-clusters according to their pedigree. The study demonstrated minimum variation or more similarity among the test hybrids as indicative of genetic consistence and can be exploited for deployment of a new hybrid variety. On other hand, the most dissimilar were the hybrid check (Ababuna) and variety check (74110) having a high genetic distance can be used for hybridization. Keywords: Analysis; Genetic correlation; Distance; Direct effect; Hybrid coffee; Indirect effect