Plus tree selection of Gmelina arborea Roxb. from Kerala, India

Abstract

Gmelina arborea Roxb., a fast-growing tree of high economic and industrial value, holds global significance for timber, agroforestry, and biomass production. Despite its versatility, systematic efforts to develop a robust selection model that integrates quantitative and qualitative traits remain limited. This study used baseline regression methods to emphasise superior morphological and physiological attributes. It selected 25 candidates plus trees (CPTs) from 169 enumerated trees across Kerala, India. Quantitative traits exhibited marked variability: tree height (11.5–16 m), girth at breast height (GBH: 0.48–2.28 m), crown width (1.8–11.2 m), and clean bole height (2.7–12.9 m), with strong correlations among height, GBH, crown width, and biomass-related traits. Principal component analysis (PCA) identified four components explaining 80% variability, with PC1 (38.6%) driven by stem quality (straightness, crown width) and PC2 (18.5%) by growth traits (height, GBH). Hierarchical clustering grouped CPTs into nine genetically distinct clusters, independent of geographic origins, underscoring inherent genetic diversity. The study establishes a framework for designing a selection index in G. arborea to optimise genetic resource management and breeding strategies for enhanced productivity and sustainable utilisation in the future.