Qualitative characterization and clustering in tomato (Solanum lycopersicum L.) germplasm accessions

Abstract

Most of the tomato genotypes are inbred in nature, indicating the need to assess and characterize germplasm accessions as they are the reserve for genotypes with desired traits. Documentation on morphological traits is quite informative in tomato breeding programs since higher levels of diversity on morphological traits are associated with genotypes with lower genetic diversity when assessed using molecular markers. The present investigation aimed to evaluate morphological diversity in tomato germplasm accessions. Morphological characterization was performed in 104 genotypes acquired from various sources. Thirty-three morphological traits, such as seedling, plant, inflorescence and fruit, were scored based on the tomato descriptors. Out of 33 characters studied, 26 traits exhibited diverse modalities, 4 traits exhibited varied classes in genotypes and 3 traits did not show any variants. Qualitative characterization highlighted greater variability among genotypes, as witnessed by their diverse modalities for each trait. The collected data was subjected to Agglomerative Hierarchical Clustering following Ward’s method. Cluster analysis and dendrogram construction displayed genetic diversity's richness in the germplasm accessions. Cluster analysis placed these 104 genotypes in six clusters. The largest cluster comprised 55 genotypes, whereas the smallest cluster had three. Agglomerative Hierarchical Clustering helped to find similarities between genotypes. This efficiently assigned genotypes into groups and thus provided guidelines for parental selection in tomato hybridization and breeding programmes.