Dissecting dwarfness in half-sib progenies of Olour mango through morpho-physiological and biochemical characterization

Mango ( Mangifera indica L.) is one of the major fruit crops. Still, its lower productivity is constrained by large tree size and the lack of reliable dwarfing rootstocks, which limit land-use efficiency and profitability. To enhance production and productivity, it is necessary to develop dwarfing rootstocks suitable for high-density planting (HDP). The present study evaluated 28 half-sib progenies of the polyembryonic Olour mango rootstock for dwarfing potential using morphological, physiological, and biochemical traits to characterise vigour and identify superior progenies for rootstock development. Significant variability was observed among half-sib progenies, with seven (OP-17–01, OP-17–10, OP-17–19, OP-17–34, OP-17–40, OP-17–47, OP-17–58) being identified as promising dwarfing traits based on integrated morphological, physiological, and biochemical evaluation. Compared with the Olour parental genotype, these progenies exhibited reduced plant height (1.02–1.64 vs. 2.01 m) and stem girth (49.56–70.81 vs 93.56 mm), increased plant height (5.92–13.75 vs. 15.42%) and stem girth (9.00–17.47 vs. 24.96%, except OP-17–47), shorter internodal length (1.82–2.55 vs. 3.45 cm), and higher bark-to-wood ratios (fresh and dry weight basis) (0.81–0.98 vs. 0.77, except OP-17–58 and 0.67–0.83 vs. 0.65, except OP-17–40 and OP-17–58) indicating dwarfing potential. These progenies also recorded reduced photosynthetic (4.49–5.46 µmol CO 2 m −2 s −1 vs. 6.29 µmol CO 2 m −2 s −1 ) and transpiration rates (0.63–3.39 m mol H 2 O m −2 s −1 vs. 3.39 m mol H 2 O m −2 s −1 ), lower stomatal density (512.00–598.67 stomata/mm 2 vs 617.33 stomata/mm 2 ), and decreased chlorophyll levels. In contrast, it showed higher levels of total phenolics (3290.00–3660.00 vs 306,333 mg/100 g) and flavonoids (228.86–256.53 vs 2026.16 mg/100 g, except OP-17–10, OP-17–30, and OP-17–40) and antioxidant capacity (263.57 to 418.10 vs 262.38 mM/g). Correlation analysis revealed positive associations between plant height, stem girth, internodal length, and chlorophyll content. In contrast, the bark-to-wood ratio, total phenolics content, flavonoids, and total antioxidant capacity were negatively associated with the vigour Multivariate analyses (PCA and hierarchical clustering) revealed moderately high variation; first four principal component explained 76.1% of the total variation, with PC1 (45.86%) differentiating dwarf from vigorous half-sib progenies based on morpho-physiological and biochemical traits, which was further supported by two-way hierarchical cluster analysis grouped progenies into distinct clusters, clearly separating dwarf (OP-17–01, OP-17–10, OP-17–19, OP-17–34, OP-17–40, OP-17–47, OP-17–58), semi-vigorous, and vigorous ideotypes. An integrated evaluation of morphophysiological and biochemical traits identified seven Olour half-sib progenies with promising dwarf phenotypes. Correlation, principal component (PCA), and hierarchical cluster analyses revealed that reduced plant height, shorter internodes, lower stem girth, a higher bark-to-wood ratio, elevated total phenolic content, and antioxidant capacity are key traits associated with dwarfing. These progenies represent promising rootstocks for high-density mango orchards and valuable genetic resources for future rootstock–scion interaction studies, marker-assisted selection (MAS), and climate-resilient breeding.