Effects of Soil Moisture Stress on Seedlings of Three Cocoa (Theobroma Cacao L.) Varieties and Selected Genotypes in Ghana

Abstract

Soil moisture stress is a major constraint to cocoa production in West Africa, particularly under changing climatic conditions. This study evaluated the response of the seedlings of three cocoa varieties and selected genotypes to soil moisture stress under greenhouse conditions. The experiment was arranged in a Completely Randomized Design (CRD) involving seven cocoa genetic materials (three varieties and four selected genotypes) subjected to four soil moisture stress treatments, each replicated four times. Pots were randomly arranged on greenhouse benches to minimize environmental variation. Cocoa seedlings were exposed to controlled soil moisture levels representing drought stress conditions. Morphological and physiological parameters, including plant height, leaf area, stem thickness, leaf and soil relative water content, chlorophyll content (NDVI), and root anatomical characteristics, were assessed.
Soil moisture stress significantly affected seedling growth and physiological performance (p < 0.05). Seedlings exposed to reduced moisture levels exhibited decreases in plant height, leaf area, and chlorophyll content compared to well-watered plants. However, certain genotypes maintained relatively higher NDVI values and improved root development under moisture stress, suggesting enhanced drought tolerance. Genotypes PA150 and Forastero showed superior drought tolerance, while PA7 and C42 were highly susceptible. Based on percent reduction from control, Forastero (23% reduction from 20.5 to 15.8 leaves) was more tolerant than Criollo (28% reduction from 21.8 to 15.8 leaves), despite similar absolute leaf counts under severe stress.
These findings highlight the importance of identifying drought-tolerant cocoa varieties or genotypes for breeding programs to improve climate resilience in cocoa production systems in Ghana and across West Africa.