Exploiting the Cocoa genetic variation for flowering time and pod development period for climate adaptation: relationship to selected yield components.

Cocoa beans from the tropical tree crop, cacao (Theobroma cacao L.) is the main ingredient in chocolates, cocoa-based confectionaries, beverages, alcohol, cosmetics and nutraceuticals. There is considerable genetic diversity within the species that falls into 10 genetic clades. The diversity is centred in the Amazonian tropics with the greatest diversity observed in populations from Peru, Bolivia, Brazil, Ecuador and Colombia. Climate change poses an important challenge to agriculture, globally, characterised by increased carbon dioxide, elevated temperature and scarcity of rainfall or changes in the rainfall pattern resulting in severe drought. Flowering time and pod development period are important physiological traits associated with geographical adaptation. Although these traits are genetically determined, very little is known regarding the genetic variation for those traits in cocoa and its populations. The presence of representative accessions from the 10 genetic groups as well asvarious geographical populations of cocoa at a single location (International Cocoa Gene Bank, Centeno, Trinidad (ICGT)), allows for a comprehensive study of genetic diversity for flowering time and pod development period without the complication of environmental influences. The study was conducted during the period April to March over two consecutive years (2016-2017 and 2017-2018) with a minimum of 10 accessions from each genetic group and from three hybrid populations. Three trees were selected and labelled and the flowering times noted. From each accession 20 flowers were tagged, and successful pod sets determined after 7 days. At least 10 pods from each accession were followed to maturity with pod length and width measurements taken at fortnightly intervals. At pod maturity the pod dimensions, the number of beans and bean size, bean weight (10 beans-fresh and dry) were determined. This study will help to understand the genetic variation for flowering time and pod development period among the geographical populations of cocoa. It will also help to understand the relationships among the various traits studied. Together this information along with geographical information could provide interesting insights into the evolutionary mechanisms that govern flowering time and pod development period, which in the future will be useful in developing accessions for climate change adaptation. 

KEY WORDS: climate resilience, genetic variation, pod maturity, average pod growth rate, pod index.