Genetic diversity, population structure and germplasm assemblage of Gmelina arborea in Eastern India for sustainable breeding and conservation

Gmelina arborea Roxb . ex Sm. is a fast-growing, commercially important deciduous tree species with significant potential for agroforestry and afforestation initiatives. However, populations of G. arborea in the Eastern Indian region remain largely uncharacterized in terms of genetic diversity and the species lacks a systematic tree improvement program in this area. The present study was undertaken to analyse the population structure and genetic diversity of G. arborea using molecular markers. In parallel, a germplasm assemblage was initiated through progeny trials to serve as the foundation tree improvement program. A field surveys was conducted over four fruiting seasons (2021–2024) and identified 434 Candidate Plus Trees (CPTs), revealing substantial phenotypic variation in key growth parameters. Three progeny trial-cum-germplasm banks were established with selected accessions for germplasm assemblage and progeny evaluation. Molecular genetic analysis using twelve polymorphic simple sequence repeat (SSR) markers detected 58 alleles (3–7 alleles per locus) with high genetic variability (average gene diversity, H e = 0.695; polymorphic information content, PIC = 0.643). Bayesian clustering revealed two major genetic lineages correlated with geographical origins, indicating a structured population. The partition of genetic variation through Analysis of Molecular Variance (AMOVA) showed that 92% of genetic variation was within populations ( F ST = 0.077), reflecting moderate genetic differentiation and ongoing gene flow. Overall, the study on population genetics and genetic diversity of G. arborea is important for further conservation decisions and tree improvement programs. Established progeny trials serve as vital conservation repositories, can be converted to seedling seed orchards after long term evaluation and can also serves as a base population for second cycle improvement.