Genetic variability and association of characters in tomato (Lycopersicon esculentum Mill.) Genotypes at humera, northern Ethiopia

Abstract

Thirty six tomato genotypes obtained from Melkassa Agricultural Research Center were tested at Humera, Northern Ethiopia, in 2010/11. A 6 x6 simple lattice design was used to estimate the extent of genetic variability, association among characters and genetic divergence among the genotypes thereby clustering them into divergent groups. Data on 24 quantitative traits were recorded and subjected to analysis. Analysis of variance for 24 quantitative traits revealed that there was highly significant difference (P<0.01) among the thirty six genotypes for all the characters studied. High phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV)(> 20 %) were recorded for number of matured fruits per plant, fruit set percentage, total fruit yield per hectare, number of fruit clusters, weight of fruits per plant, number of seeds per fruit, average single fruit weight, number of fruits per fruit cluster, number of flowers per plant, number of secondary branches per plant, locule number, pericarp thickness, days to maturity, days to 50 percent fruiting and shape index. All the traits except number of primary branches per plant (47.36%) had very high heritability (> 80 %) indicating these traits were less influenced by environmental factors and selection for them is fairly easy. High GCV along with high heritability and genetic advance was obtained for number of matured fruits per plant, fruit set percentage, total yield per hectare, number of seeds per fruit, number of fruit clusters per plant, average weight of fruits per plant and average single fruit weight per plant indicating that the characters can be improved through selection. Fruit yield per hectare had positive and highly significant phenotypic and genotypic correlation with average weight of fruits per plant, number of matured fruits per plant, fruit set percentage, number of fruit clusters per plant, number of pickings and number of fruits per fruit cluster while it showed negative and highly significant genotypic and phenotypic correlation with days to 50% fruiting, days to maturity and days to 50% flowering. Estimates of genotypic direct and indirect effects of various characters on fruit yield (tonnes/ha) showed that number of matured fruits per plant and average weight of fruits per plant had the highest positive direct contribution to fruit yield indicating that selection based on these characters will improve fruit yield. However, fruit set percentage, fruit polar diameter, days to 50 % fruiting and number of fruits per cluster exerted negative direct effect on fruit yield per hectare. Cluster analysis revealed that the 36 genotypes were grouped in to 6 distinct clusters. Distance between clusters showed very highly significant difference for all traits considered. The maximum and minimum distances were recorded between clusters IV and V (1805.00) and cluster II and III (81.94). This indicated the existence of a possibility to improve genotypes through hybridization from any pair of clusters and subsequent selection can be made from the segregant generations. Principal component analysis showed that the first six principal components explained about 83.03% of the total variation. It can be suggested that more number of genotypes in multiple location and season may be tested with due attention given to fruit yield, disease and pest resistant, fruit size and shelf life characteristics.