Bean counting

Cilas, C and F. Ribeyre, 2015.

Edited by Dr. Marissa Moses and Dr. Lambert Motilal (Cocoa Research Centre, The UWI St. Augustine Campus) of a Paper presented at the International Fine Cocoa Innovation Centre Conference & Symposium, Trinidad and Tobago, March 23-24, 2015.

Productivity is a numbers game but for cocoa, it isn’t as simple as adding one bean on top of another.

Growing a crop in the tropics is fraught with numerous challenges and cocoa is no exception. From poor soils to many diseases, cocoa farmers are hard pressed to bring in a successful harvest. No matter the difficulty though, farmers need high productivity to recoup their investment and realise a profit.
Productivity is a numbers game but for cocoa, it isn’t as simple as adding one bean on top of another. There are forces that can take away a bean from the pile and there are steps you can take to ensure a big pile, yet sometimes, even after you have used the recommended variety for your area, you crack open a pod (Figure 1) and there are only twenty beans nestled in the meaty, white flesh, when you expected fifty. What does the latest research advise to avoid such unprofitable surprises?

Depending on the cocoa market you provide for such as cosmetics and nutraceuticals versus chocolatiers, the weight of cocoa beans produced per tree may surpass the need for a superior tasting product. Unfortunately the genetic dice rolled a losing hand in this instance as the association (also called heritability value) of that trait is weak, meaning that the environment plays a hefty role in deciding how many pods survive to maturity on your tree. This means the weight of cocoa beans produced per tree can fluctuate from one growing season to the next. According to scientists, the association between genetics and the weight of cocoa beans produced per tree can be as low as 0.1-0.4 (a measurement where a value closer to 1 is great but near to 0 is awful). We have more luck though when it comes to bean mass with an association strength as high as 0.9 in some cases. So what about bean number per pod, you may wonder? Once proper disease management is carried out, is there a predictable number of beans inside each pod? The researchers at the CIRAD (French Agricultural Research Centre for International Development) have pondered the same question.

In an effort to evaluate the strength of the association of this trait, they have examined a number of clones grown in the Ivory coast, Togo and Brazil. These included for instance IMC 67, LCT 37A, CCN 51, GNV 11-53, AMCC 5 and UF 677. The researchers also chose clones which were self-compatible (typified by high pollination levels) and those which were self-incompatible (typified by low pollination levels) to make a robust evaluation. From their experiment, it was found that the number of beans per pod followed three modes of distribution. The clones that normally had high pollination levels were skewed to the right meaning a high number of beans per pods, and vice versa. However, they found that some low pollination clones had variable amounts of beans per pod, with numbers as high as those varieties that are self-compatible or high pollination clones. These clones therefore had more or less a symmetric distribution. Unfortunately upon calculation, the degree of association of this trait was found to be low, with a heritable value of 0.17. This low heritability value means that the environment affects the number of beans eventually produced in a pod, and is therefore not predictable from one growing season to the next. Agronomic management that support pollination, and breeding for improved pollination levels are therefore suggested to increase the mean number of beans in a pod.

How do your pods compare? In this bean counting study the highest number was 44 beans per pod.

To read more about these studies we recommend

  1. Cilas, Christian, Regina Machado, and Juan-Carlos Motamayor (2010). “Relations between several traits linked to sexual plant reproduction in Theobroma cacao L.: number of ovules per ovary, number of seeds per pod, and seed weight.” Tree genetics & genomes 6, no. 2: 219-226.