Assessment of Rice Varieties from Ghana under Mild Water Stress at Both Early Seedling and Reproductive Stages

Abstract

Drought is a major climatic constraint, reducing rice physiological performance and biomass accumulation by over 30% across growth stages. This study examined drought responses of nine rice varieties released in Ghana in August 2022, focusing on seedling and reproductive stages. The set comprised six lowland types (CRI-Korea Mo, CRI-Kang Mo, CRI-Agyapa, CRI-Baakoye, CRI-Tuo Mo, CRI-Onuapa) and three upland types (CRI-Ofosu, CRI-Cho, CRI-KAFACI). A 2 × 9 factorial within a randomized complete block design, with six replications, was conducted in a controlled screen house. Water stress was imposed at 30% of water-holding capacity, while controls were maintained at 100%. Physiological traits assessed included photosystem II quantum yield, leaf greenness, relative leaf water content, and morphological parameters such as leaf area and plant height, measured after 7 and 14 days of stress. ANOVA revealed significant drought effects (P ≤ 0.05) on most variables, whereas genotype and interaction effects were generally non-significant (P ≥ 0.05). Notably, all genotypes exhibited ~70% reductions in photosystem II efficiency, leaf area, and grain yield compared to well-watered controls. These findings suggest that lowland and upland rice varieties responded similarly under drought conditions, highlighting the need for breeding programs targeting enhanced drought resilience.

Keywords: Drought, Physiological performance, Reproductive stage, Rice, Seedling stage