Root traits and biomass production of drought-resistant and drought-sensitive arabica coffee varieties growing under contrasting watering regimes

Drought is a major factor affecting coffee production, and different genotypes exhibit varying degrees of resistance to drought stress. We examined root traits and biomasses of drought-resistant (74110, Angafa, Bultum, Chala, and Gawe) and drought-sensitive (75227, Koti, Melko CH2, Menasibu, and Mokah) Coffea arabica varieties at seedling stage under contrasting watering regimes (water stressed and well watered) for 30 days followed by 15 days of recovery to identify the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of arabica coffee varieties. We used a split-plot design with three blocks, where watering regime was the whole-plot factor and variety was the subplot factor. During water-stress and recovery periods, the interaction effect between watering regime and variety significantly affected root traits and dry matter partitioning, while the watering-regime main effect affected biomass. We observed a higher (1) tap root diameter (0.34 cm), lateral root number (80.7), and root volume (4.7 cm⁻³) for 74110; (2) lateral root number (79.3), specific root length (24.8 cm g⁻¹), and root-mass ratio (0.41 g g⁻¹) for Bultum; and (3) root length density (3.3–5.2 cm cm⁻³), root angle (42.6°–47.8°), root-mass ratio (0.40–0.42 g g⁻¹), and root-shoot ratio (0.67–0.72 g g⁻¹) for Angafa, Chala, and Gawe under water-stressed condition. During both study periods, biomasses were much lower under water-stressed than under well-watered condition. The findings show the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of young arabica coffee.