Clonal Cocoa Varieties Growth and Leaf Non-Structural Carbohydrate Response to Field Stress Conditions

This study investigated the growth and leaf metabolism of clonal cocoa varieties in response to field stress conditions during wet and dry seasons. It was hypothesized that clonal cocoa varieties differ in their growth, photochemical efficiency, relative water content and central carbon metabolism under seasonal field stress conditions. Fourteen cocoa clone varieties between 35 and 44 months after planting were evaluated. Using various standard procedures in the field and laboratory, the plants were assessed in both wet (as unstress condition) and dry (as stress condition) seasons field conditions. Soil moisture content, photochemical efficiency, relative water content, non-structural carbohydrate, carbon, nitrogen, growth and pod numbers were measured and compared among the seasons. The clones conserved cellular water, and this manifested in high levels of relative water content. Photochemical efficiency reduced in most of the clonal cocoa varieties during the dry season. Soluble sugars, starch and non-structural carbohydrate accumulated in the leaves of the plants during the dry season. The levels of carbon and nitrogen were significantly high and low respectively in the dry season. Some clonal cocoa varieties increased growth rate and had a greater number of pods. The correlation analysis revealed a relationship among non-structural carbohydrate, growth and physiological traits. Clone varieties CRG 0132/105, CRG 0145/205, CRG 0314/102 and T65/238 were the most tolerant in response to field stress conditions, and this reflected in the accumulation of soluble sugars, starch and non-structural carbohydrate, improved photosynthetic efficiency, conserved cellular water and enhanced growth rates and pod numbers agreeing to the hypothesis.