Integrative analysis of phenotypic and ISSR marker-based genetic diversity in Tabernaemontana divaricata genotypes

Abstract

Tabernaemontana divaricata (L.) R.Br. ex Roem. & Schult. is an important ornamental and medicinal shrub exhibiting considerable phenotypic variability, yet its genetic diversity remains underexplored. The present study aimed to assess genetic variability among twelve genotypes using an integrated approach combining morphological traits and Inter Simple Sequence Repeat (ISSR) markers. Fourteen quantitative and qualitative morphological traits were evaluated to estimate phenotypic and genotypic coefficients of variation, heritability, and genetic advance. High variability, heritability, and genetic advance were observed for key traits such as chlorophyll content, flower bud length, and yield, indicating strong additive gene action and selection potential. Principal component analysis revealed that five components explained 88.20% of total variation, with vegetative vigor, physiological efficiency, and floral traits contributing significantly. Cluster analysis based on morphological data grouped genotypes into three distinct clusters.

Molecular characterization using 13 ISSR primers generated 215 bands, of which 191 were polymorphic, with an average polymorphism of 88.50%. The polymorphic information content (PIC) ranged from 0.16 to 0.94, indicating moderate to high marker informativeness. UPGMA clustering based on ISSR data also grouped genotypes into three major clusters, revealing substantial genetic divergence. Similarity coefficients ranged from 0.181 to 0.625, reflecting moderate genetic diversity among genotypes. The concordance between morphological and molecular analyses highlights the effectiveness of integrated approaches in genetic diversity studies. Overall, the study demonstrates significant genetic variability in T. divaricata, providing valuable insights for germplasm conservation, selection of divergent parents, and development of improved genotypes for floricultural and pharmaceutical applications.