Growth and nutritional responses of juvenile wild and domesticated cacao genotypes to soil acidity

Authors: AHNERT, DARIO - University Of Santa Cruz - Brazil; PAIVA, ARLICELIO - University Of Santa Cruz - Brazil; ALMEIDA, ALEX-ALAN - University Of Santa Cruz - Brazil; DE ARAUJO, QUINTINO - University Of Santa Cruz - Brazil; Zhang, Dapeng; BALIGAR, VIRUPAX - Retired ARS Employee

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2022
Publication Date: 12/9/2022
Citation: Ahnert, D., Paiva, A., Almeida, A.F., De Araujo, Q.R., Zhang, D., Baligar, V.C. 2022. Growth and nutritional responses of juvenile wild and domesticated cacao genotypes to soil acidity. Agronomy. https://doi.org/10.3390/agronomy12123124.
DOI: https://doi.org/10.3390/agronomy12123124

Interpretive Summary: Drought is an emerging threat to cacao production worldwide. The impact of drought is especially significant to small cacao farmers who do not have capacity to irrigate their plantations. Evaluation and selection of cacao germplasm tolerance to drought stresses are vital for cacao genetic improvement under climate changes. The main objective of this study was to evaluate local Brazilian cacao germplasm for drought tolerance. Mother trees of 83 clones were selected from various farms in a region of Bahia, Brazil that suffered serious droughts in the last 10 years. The selected candidate genotypes were considered Drought Tolerant Clones (DTC) based on preliminary observations. From these clones, vegetative cuttings were propagated and evaluated using pot experiments in greenhouse conditions where different drought conditions were evaluated. Significant difference was observed among the cacao clones. The top 10 clones were selected as promising lines for breeding new cacao varieties with enhanced drought tolerance. Our result also showed that the drought tolerance indexes are useful indicators to characterize cacao clones for their response to drought stress. This information will be used by cacao breeders, agronomists and growers to select drought-tolerant cacao clones for crop production and for genetic improvement

Technical Abstract: Drought is an emerging threat to cacao production worldwide. The impact of drought is especially significant to small cacao farmers who do not have capacity to irrigate their plantations. Evaluation and selection of cacao germplasm tolerance to drought stresses are vital for cacao genetic improvement under climate changes. The main objective of this study was to evaluate local Brazilian cacao germpalsm for drought tolerance, based on indicators of physiological features. A total of 83 putative drought tolerant clones (DTC) were selected from the drought-prone region of Bahia, Brazil. Seedlings of the DTC and two tester clones (CCN51- drought intolerant and CEPEC2002 – drought tolerant) were propagated by rooted cuttings of plagiotropic branches. Pot experiments were conducted in randomized block design with three replications in greenhouse condition. DTC and tester clones were submitted to different treatment of soil moisture contents [70, 60, 50, 40 and 30% of field capacity (FC)] and their controls (maintained close to 100% of FC) by a period of 40 to 60 days. Data were analyzed using univariate and multivariate statistical analysis. Significant differences were observed among clones and drought treatment (70, 60, 50, 40, and 30% of FC) on measured physiological traits. Ten DTC clones were identified to have better drought-tolerance as indicated by different physiological parameters, such as net photosynthesis, stomatal conductance, leaf transpiration, internal CO2 in the leaf mesophyll intrinsic and instantaneous efficiencies of water use. These clones were selected as promising parental lines for breeding new cacao varieties with enhanced drought tolerance. Our result also showed that drought tolerance indexes are useful indicators to characterize cacao clones for their response to drought stress.