Screening for drought tolerance potential of nine cocoa (Theobroma cacao L.) genotypes from Ghana

This study was conducted with a view to screen nine genotypes of Cacao from The Cocoa Research Institute of Ghana (CRIG) to test their abilities to withstand drought stress conditions using parameters such as leaf relative water content (RWC), proline accumulation in leaves and trichomes. The experimental design consisted of three replicates of the genotypes used and these were laid out in Complete Randomized Block Design (CRBD) to determine the drought tolerance potentials of the nine genotypes of cocoa at the seedling stage. Two water treatments were used which involved withholding water from one day after full saturation with water prior to the first appearance of drought symptoms (FADS) and watering every two days to the completion of the experiment. Results in this research revealed that proline was found to gather in water-stressed seedlings, and the differences in the mean proline amounts in the genotypes was found to be significant. Genotype T63/971 x Sca9 had the most elevated concentration of free proline at FADS (4 μg/g DW) followed by genotype T60 x Pound10 (3.5 μg/g DW) whereas genotype PA150 × 9006 had the smallest amount of accumulated proline in leaves. Genotype PA150 × 6020 had the highest RWC and SMC of 65% and 1.5% respectively at FADS whilst genotype PA7 x 6035 had the lowest RWC of 43%. There was a direct relationship between the amounts of free proline of genotypes T63/971 x SCA9 and T60 x POUND10 and their respective RWC of the leaves. Genotypes T63/971 x SCA9 and PA150 × 9006 had the highest and lowest numbers of trichomes respectively. Inference from this study revealed that T63/971 x SCA9 and T60 x POUND10 genotypes appear to be the most drought-tolerant genotypes in view of their relatively high values of free proline content, leaf RWC, trichomes and lower values of soil water use (SMC).