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Research Article
Variability in the pod and bean characteristics and their relationship with leaf nutrient content in cocoa (Theobroma cacao L.)
expand article info Bhavishya‡§, Ravi Bhat§, S. Elain Apshara|, T. N. Pushpa‡, D. Srikantaprasad‡#, H. Nayana|, S. H. Thube‡¤, R. T. P. Pandian|, S. V. Ramesh§
‡ UHS-Kittur Rani Channamma College of Horticulture, Arabhavi, India
§ ICAR-Central Plantation Crops Research Institute, Kasaragod, India
| ICAR-Central Plantation Crops Research Institute, Regional Station, Vittal, India
¶ UHS-College of Horticulture, Kolar, India
# UHS-Horticulture Research and Extension Centre, Hogalagere, India
¤ ICAR-Central Institute for Cotton Research, Nagpur, India

Corresponding author: Bhavishya ( bhavishya@icar.gov.in )

Academic editor: Hamza Sohail
© 2024 Bhavishya, Ravi Bhat, S. Elain Apshara, T. N. Pushpa, D. Srikantaprasad, H. Nayana, S. H. Thube, R. T. P. Pandian, S. V. Ramesh.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Bhavishya, Bhat R, Apshara SE, Pushpa TN, Srikantaprasad D, Nayana H, Thube SH, Pandian RTP, Ramesh SV (2024) Variability in the pod and bean characteristics and their relationship with leaf nutrient content in cocoa (Theobroma cacao L.). Innovations in Agriculture 7: 1-7. https://doi.org/10.3897/ia.2024.126141
Open Access

Abstract

Theobroma cacao L., cocoa, produces fruits throughout the year with one or two peaks. The relationship between pod or bean characteristics and leaf nutrient status in cocoa genotypes grown in the humid tropics of India is not well documented. Our investigation found notable differences amongst twenty genotypes of cocoa for pod weight, husk weight, bean count, fresh bean weight pod, single dry bean weight, nib recovery, and shell percentage. Single dry bean weight is an important parameter of the cocoa beans for the industry, and it was significantly associated with the husk weight, pod weight, and nib recovery. The weight of the dry bean was found to be higher in pods with higher pod weight and husk weight. However, it decreased significantly with increased bean count per pod. Higher nib recovery is another important industry trait and was closely associated with single dry bean weight. Pearson’s correlation coefficients indicated pod and bean characteristics in different genotypes had no significant association with leaf nutrient status. Even, the nutrient ratios had no tangible influence on the pod/bean traits, except for K/P and Ca/B, which had significant associations with the husk weight and pod count per tree, respectively.

Keywords

Theobroma cacao, bean, pod, nutrient

Introduction

Theobroma cacao L. (Malvaceae), commonly known as the “food of gods,” is the most ancient beverage crop grown in tropical countries. It is native to the Amazonian basin (Wood and Lass 2001). It is one of the most economically important perennial tropical crops, cultivated primarily for its beans, which are used in the chocolates and confectioneries. Cocoa is grown in over 10 million ha in more than 58 countries, producing 52,42,000 t dry beans (ICCO 2020). It is grown in agroforestry systems in major cocoa growing countries in South America and Africa but mixed-cropped in Asian countries. In Southern India, cocoa is grown in Karnataka and Kerala states, traditionally as a mixed crop and is gaining importance, and area expansion is observed in other non-traditional regions of Tamil Nadu and Andhra Pradesh states. It is grown in an area of 1,03,376 ha, mainly as a component crop in palm based cropping system, with a production of 27,072.15 t of dry beans (DCCD 2021).

Cocoa bear pods throughout the year, depending on the prevailing agro-climatic conditions, with one or two peaks. After pollination, these hard-walled pods take five to six months to mature and contain twenty to forty seeds, which are marketed after being fermented and dried (Toxopeus 1985). The colour of the fruit, bean size, and butter content will vary with the varieties/cultivars (Asna et al. 2014; Elain Apshara 2017), and the quantitative characteristics of the pod and bean have been utilized to evaluate genetic diversity in cocoa (Toxopeus 1985; Ollerton et al. 2011). There is a noticeable variation between the genotypes in the pod’s weight, length, breadth, husk:bean ratio, and quantity of beans per pod (Elain Apshara 2017).

Numerous elements, such as size, count, color, acidity, flavor, level of bitterness, polyphenol content, fermentation quality, and nutritional makeup, affect the quality of cocoa beans. The economic part of cocoa is beans, and its size is an important factor in deciding the yield (Soria 1978). Small beans are difficult to process and have a greater shell content, hence bean size is economically important factor for the industry. The processing industries prefer beans weighing one gram or more. The morphological and structural characteristics of beans often exhibit variability among cocoa accessions (Adewale et al. 2010). Great differences exist in the size, shape, color, and quality of the beans between and within cocoa varieties (Enríquez and Soria 1968).

A common method for determining the nutritional state of cocoa trees is leaf nutrient analysis (Paramo et al. 2016; van Vliet and Giller 2017). Nutrient uptake, the process by which nutrients move from the external environment into the plant, is vital for maintaining optimal growth and yield. Pod production in cocoa is primarily influenced by the availability of nutrients within the tree at various stages ranging from flower initiation to pod maturity (Hutcheon 1976). Numerous studies have been conducted on variations in nutrient absorption and use between and among crops (Fageria and Baligar 2005). However, the studies on the relationship between leaf nutrient status and the pod/bean characteristics are very limited in cocoa. Hence, the variability in the pod and bean characteristics in cocoa genotypes, and their relationship with leaf nutrient content was studied in 20 cocoa genotypes.

Material and methods

Experimental location

The experiment was conducted at ICAR-Central Plantation Crops Research Institute, Regional Station, Vittal, India as explained in our earlier study (Bhavishya et al. 2024).

Plant materials

This study used four released hybrids and their parents, one clone planted in 2005, and eight upper Amazon genotypes planted in 2007. Cocoa was grown as a mixed crop with arecanut.

Pod characteristics

The main harvesting season was April – July. The cocoa pods were harvested as and when they ripened.

Average pod weight (g): Five pods were selected randomly and weighed, and the mean value was calculated.

Average husk weight per pod (g): Five ripened pods were harvested randomly, broken using a wooden hammer, and the beans and placenta were removed. The husks of these five pods were weighed, and the mean value was given as average husk weight pod-1.

Average number of beans per pod: The wet beans of five pods used to calculate the average husk weight were counted, and the mean value was given as the average number of beans pod-1.

Average fresh bean weight per pod (g): The wet beans of five pods used to calculate the average husk weight were weighed, and the mean value was given as average fresh bean weight pod-1.

Pod to wet bean ratio: Pod to wet bean ratio was calculated using the formula given by Elain Apshara (2017).

Bean characteristics

The wet beans were fermented in small perforated trays for 6 days, then oven-dried at 55 °C to get the dry beans. The following bean characteristics were recorded.

Single dry bean weight (g): Exactly 100 dry beans were weighed, and the value was divided by 100 to determine the dry weight of a bean.

Nib recovery (%): One hundred dry beans were taken and weighed. The beans were broken to separate the shell and nib. The nib’s weight was recorded, and the nib recovery was calculated using the following formula.

Nib recovery (%)=Weight of the nib (g)Weight of the dry bean (g)×100

Shell percentage was calculated using the following formula,

Shell percentage (%)=Weight of the shell (g)Weight of the dry bean (g)×100

Nutrient estimation

Nutrient analysis was done from mature leaves (the second leaf of the last maturing flush) by following standard methods (Piper 1966; Jackson 1973; Gupta 1979) as explained earlier (Bhavishya et al. 2024).

Data analysis

Data was collected from 20 cocoa genotypes in three replications. The data were analyzed using standard analysis of variance (ANOVA) technique (Gomez and Gomez 1984). The data was subjected to RCBD analysis of variance with three replications using SPSS at a 5 percent significance level.

Results and discussion

Pod characters in cocoa genotypes

Pod characters, i.e., single pod weight, husk weight per pod, fresh bean weight per pod, and bean count, varied significantly among the different cocoa genotypes (Table 1). In 2019, the single pod weight varied from 189 g to 379 g among different genotypes. Cocoa genotype VTLC 66 recorded the highest single pod weight and husk weight per pod (265 g); whereas VTLC 156 registered the lowest single pod weight (189 g) and husk weight per pod (130 g). In 2020, single pod weight was 204–593 g in different cocoa varieties. VTLC 30A stood out with significantly higher single pod weight (593 g) and husk weight (314 g). Variability in pod characters in cocoa was reported by Subramanian and Balasimha (1981), Mallika et al. (1996), and Elain Apshara et al. (2008).

In 2019, VTLCH 3 showcased the highest fresh bean weight of 152 g. However, in 2020, the genotype VTLC 30A recorded a maximum fresh bean weight of 156 g. Genotypic variation in cocoa bean weight can be attributed to the diverse genetic makeup of cocoa plants. Different genotypes possess unique combinations of genes that influence pod development, seed formation, and growth. Environmental factors, including climate and soil conditions, further contribute to this variation. Such variation was also reported by Asna et al. (2014).

Seed count in a pod is a gene controlled character (Glendinning 1963). It also depends on several factors, including environment (De Reffye et al. 1978; Falque et al. 1995; da Silva et al. 2016). These factors include the number of ovules per ovary, the fertility of the ovules, which varies depending on the self-compatibility or self-incompatibility of the cocoa genotype, and natural pollination conditions. In this study, significant variation was observed for bean count. In 2019, the genotypes VTLC 182 and VTLC 185 stood out, with the highest average bean number being 46 per pod. In 2020, VTLC 185 exhibited the highest average bean number of 52.

On the other hand, the genotype VTLC 148 had the lowest average bean numbers of 33 and 24 in 2019 and 2020, respectively. Differences in total count of beans pod-1 in various cocoa genotypes was reported by Enriquez and Soria (1968) and Lachenaud and Oliver (2005). However, a higher bean count is not an important indicator of good traits because a greater number of beans with small bean sizes is not recommended (Engles 1982). There is a strong relationship between pod weight and bean count (Table 3), which confirms the previous studies (Enriquez and Soria 1968; Cilas et al. 2010). Beans in pods with more beans are a little lighter. It could be due to the competition amongst beans within pods (Doare et al. 2020). However, based on the genotypes, this effect appears to vary.

Table 1.
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Pod characters in selected cocoa genotypes during 2019 and 2020.

SI No Genotypes 2019 2020 Mean of 2019 and 2020
Single pod weight (g) Husk weight pod-1 (g) Fresh bean weight pod-1 (g) Average bean number pod-1 (g) Single pod weight (g) Husk weight pod-1 (g) Fresh bean weight pod-1 (g) Average bean number pod-1 (g) Single pod weight (g) Husk weight pod-1 (g) Fresh bean weight pod-1 (g) Average bean number pod-1 (g)
1 VTLCH 1 350 247 103 35 302 199 103 38 326 223 103 37
2 VTLCH 2 347 231 116 38 204 137 67 38 275 183 91 38
3 VTLCH 3 363 211 152 34 445 304 142 39 404 257 147 38
4 VTLCH 4 284 199 85 36 306 217 90 39 295 208 87 37
5 VTLCC 1 221 134 87 40 322 196 126 42 272 165 107 41
6 VTLC 01 248 162 86 37 449 326 124 41 349 244 105 39
7 VTLC 05 272 173 99 34 332 232 99 37 302 202 99 35
8 VTLC 11 299 219 80 38 345 251 95 40 322 235 87 39
9 VTLC 19A 273 174 99 38 403 266 137 43 338 220 118 41
10 VTLC 30A 328 192 136 35 593 437 156 35 460 314 146 35
11 VTLC 61 320 228 92 36 338 224 115 46 329 226 103 40
12 VTLC 66 379 265 114 40 318 216 102 40 348 240 108 40
13 VTLC 148 331 222 108 33 286 206 81 24 309 214 95 28
14 VTLC 150 301 194 108 41 242 158 84 35 271 175 96 38
15 VTLC 151 370 259 111 37 370 259 111 37 370 259 111 37
16 VTLC 154 363 258 105 36 371 256 115 39 367 257 110 37
17 VTLC 155 319 218 101 37 395 274 122 39 357 246 112 38
18 VTLC 156 189 130 59 41 310 208 102 45 249 169 81 43
19 VTLC 182 261 152 109 46 211 131 81 45 236 142 95 46
20 VTLC 185 300 203 97 46 410 279 131 52 355 241 114 48
Mean 306 203 102 38 348 239 109 40 327 221 106 39
CD at 5% 69.9 49.4 31.4 6.5 126.0 91.0 42.0 5.0 77.8 55.2 27.5 3.8

Bean characteristics in cocoa genotypes

The processing units favor beans weighing one gram or more. Fermented and dried beans were measured for bean traits. Bean characteristics like single dry bean weight (SDB), nib recovery, and shell percentage varied significantly among cocoa genotypes (Table 2). Single dry bean weight is an important trait with high heritability (Cilas et al. 2010). The chocolate industry is interested in two bean size characteristics: uniformity and largeness. Thus, it’s essential to consider the average weight of cocoa beans as an important factor in the genetic improvement of cocoa (Doare et al. 2020). According to Enriquez and Soria (1968), the dry weight of beans varies greatly depending on the accession, ranging from 0.5 g to 2.5 g. However, the range seen in this study was 0.69 g to 1.1 g. This could be due to the differences in the accessions used in the present study. Upper Amazon genotype VTLC 151 recorded a higher single dry bean weight of 1.10 and 1.11 g in 2019 and 2020, respectively. In contrast, VTLC 156 (0.62 g) and VTLC 182 (0.63 g) exhibited the lowest single dry bean weight in 2019 and 2020, respectively. Variability in single dry bean weight among cocoa genotypes is well documented (Elain Apshara et al. 2009; Elain Apshara 2015).

Single dry bean weight was significantly associated with the husk weight (r = 0.57) and pod weight (r = 0.53) of cocoa (Fig. 2). This suggests that the weight of the dry beans increases with higher weight of the pod and husk. However, SDB weight decreased significantly with increased bean count per pod (r = -0.63).

Higher nib recovery is also another important trait for the industry. In 2019, the highest nib recovery was obtained in VTLC 11 (85.1%), whereas, the least nib recovery was recorded in VTLC 156 (79.4%). In 2020, VTLC 148 exhibited the highest nib recovery rate (86.3%), while the lowest nib recovery was recorded in VTLC 61 (79.4%). Shell percentage was significantly lower in genotypes with high nib recovery and vice versa. Such variability in nib recovery and shell percentage was observed in the evaluation of cocoa genotypes in the humid tropics of Karnataka (Elain Apshara et al. 2009; Elain Apshara 2015), Gujarat (Bhalerao et al. 2018), and Assam (Singh et al. 2020). Pearson’s correlation coefficient indicated that single dry bean weight and nib recovery were significantly associated (r = 0.64). Hence, single dry bean weight is an important bean trait, as the nib recovery is more in bolder beans (Fig. 1).

Mineral nutrients play a major role in the yield and quality of cocoa (Verlière 1981). Incomplete pod filling appears to result from interactions between nutritional factors and genotypes, and the application of boron was found to increase bean count while decreasing the occurrence of flat beans (Lachenaud 1995). However, the leaf nutrient status had no significant effect on the flowering, fruit set, and cherelle wilt in cocoa, except for calcium which had a significant association with fruit set percentage (Bhavishya et al. 2024). In this study, Pearson’s correlation coefficients indicated no tangible association of leaf nutrients with the single dry bean weight, nib recovery, and shell percentage (Table 3). The result is in line with Noordiana et al. (2007), and they observed no significant effect of nutrient treatments on the pod weight, shell weight, bean count and single dry bean weight in two cocoa clones in Malaysia.

The relationship between the leaf mineral nutrient ratios and pod/bean traits was studied (Table 4). The nutrient ratios had no tangible influence on the pod/bean traits, except for K/P and Ca/B, which had significant associations with the husk weight and pod count per tree, respectively.

Table 2.
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Bean traits in twenty cocoa genotypes.

SI No Genotypes 2019 2020 Mean of 2019 and 2020
Single dry bean weight (g) Nib recovery (%) Shell percentage (%) Single dry bean weight (g) Nib recovery (%) Shell percentage (%) Single dry bean weight (g) Nib recovery (%) Shell percentage (%)
1 VTLCH 1 1.04 83.3 16.7 0.97 84.5 15.5 1.00 83.9 16.1
2 VTLCH 2 0.94 83.2 16.8 0.90 83.0 17.0 0.92 83.1 16.9
3 VTLCH 3 0.84 80.9 19.1 1.00 82.8 17.2 0.92 81.9 18.1
4 VTLCH 4 0.97 83.7 16.3 0.91 83.6 16.4 0.94 83.7 16.3
5 VTLCC 1 0.96 83.2 16.8 1.00 84.7 15.3 0.98 84.0 16.0
6 VTLC 01 0.94 83.9 16.1 0.97 85.6 14.4 0.95 84.8 15.3
7 VTLC 05 0.90 80.2 19.8 0.84 80.2 19.8 0.87 80.2 19.8
8 VTLC 11 0.97 85.1 14.9 0.94 83.0 17.0 0.96 84.1 15.9
9 VTLC 19A 0.96 82.7 17.3 0.94 82.0 18.0 0.95 82.4 17.6
10 VTLC 30A 0.98 83.5 16.5 1.06 80.2 19.8 1.02 81.8 18.2
11 VTLC 61 0.90 80.5 19.5 0.67 79.4 20.6 0.79 80.0 20.1
12 VTLC 66 1.01 82.9 17.1 0.87 83.1 16.9 0.94 83.0 17.0
13 VTLC 148 1.04 84.5 15.5 1.00 86.3 13.7 1.02 85.4 14.6
14 VTLC 150 0.75 82.2 17.8 0.65 83.7 16.3 0.70 83.0 17.0
15 VTLC 151 1.11 84.7 15.3 1.10 86.1 13.9 1.10 85.4 14.6
16 VTLC 154 1.00 83.8 16.2 0.95 83.0 17.0 0.98 83.4 16.6
17 VTLC 155 1.05 83.7 16.3 1.02 85.8 14.2 1.04 84.8 15.2
18 VTLC 156 0.62 79.4 20.6 0.76 85.7 14.3 0.69 82.6 17.5
19 VTLC 182 0.76 81.6 18.4 0.63 81.4 18.6 0.70 81.5 18.5
20 VTLC 185 0.77 81.1 18.9 0.65 80.3 19.7 0.71 80.7 19.3
Mean 0.93 82.7 17.3 0.89 83.2 16.8 0.91 83.0 17.0
CD at 5% 0.10 3.1 3.1 0.27 3.7 3.7 0.16 2.30 2.30
Figure 1. 

Web plot of the correlation matrix.

Figure 2. 

Pearson’s correlation coefficients for leaf nutrient status vs pod/bean traits.

Table 3.
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Pearson’s correlation coefficients for leaf nutrient status vs pod and bean characters in cocoa.

Pod/bean characters N P K Ca Mg Fe Mn Cu Zn B
Single pod weight 0.19 -0.09 0.15 -0.37 -0.12 -0.13 -0.05 0.04 0.18 -0.22
Husk weight pod-1 0.23 -0.06 0.22 -0.40 -0.09 -0.10 -0.14 -0.07 0.10 -0.22
Fresh bean weight pod-1 0.05 -0.14 -0.03 -0.21 -0.14 -0.19 0.15 0.31 0.33 -0.17
Average bean number pod-1 0.07 0.16 0.10 0.16 -0.02 -0.23 -0.04 0.04 -0.07 -0.05
Single dry bean weight 0.11 0.01 0.17 -0.27 -0.16 0.12 -0.35 -0.21 0.11 -0.33
Nib recovery -0.12 -0.03 0.07 0.02 0.12 -0.17 -0.04 -0.05 -0.14 -0.38
Shelling percentage 0.13 0.03 -0.07 -0.02 -0.11 0.18 0.04 0.05 0.14 0.38
Number of pods tree-1 0.19 0.19 0.29 -0.23 -0.11 0.39 -0.41 0.12 0.35 0.37

N: Nitrogen; P: Phosphorous; K: Potassium; Ca: Calcium; Mg: Magnesium; Fe: Iron; Mn: Manganese; Cu: Copper; Zn: Zinc; B: Boron.
Table 4.
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Pearson’s correlation coefficients for leaf nutrient ratios vs pod and bean characteristics in cocoa.

Pod/bean characters N/K N/P K/P K/Ca K/Mg Ca/Mg K/Fe K/Mn K/Zn Ca/B P/Zn
Single pod weight -0.06 0.40 0.43 0.31 0.20 -0.32 0.28 0.08 -0.06 -0.16 -0.24
Husk weight pod-1 -0.11 0.36 0.44* 0.37 0.25 -0.35 0.31 0.18 0.02 -0.19 -0.18
Fresh bean weight pod-1 0.08 0.39 0.31 0.11 0.04 -0.16 0.18 -0.17 -0.24 -0.06 -0.32
Average bean number pod-1 -0.22 -0.14 -0.06 -0.13 0.00 0.17 0.32 0.01 0.14 0.17 0.18
Single dry bean weight -0.15 0.14 0.27 0.31 0.26 -0.17 0.01 0.28 -0.03 0.00 -0.16
Nib recovery -0.23 -0.07 0.13 0.10 0.03 -0.01 0.10 0.08 0.21 0.27 0.11
Shell percentage 0.22 0.06 -0.13 -0.10 -0.03 0.01 -0.10 -0.08 -0.21 -0.28 -0.11
Number of pods tree-1 -0.33 -0.13 0.06 0.26 0.25 -0.11 -0.09 0.35 -0.17 -0.44* -0.12
Pod to wet bean ratio -0.18 0.02 0.18 0.31 0.26 -0.24 0.24 0.40 0.23 -0.38 0.09

N: Nitrogen; P: Phosphorous; K: Potassium; Ca: Calcium; Mg: Magnesium; Fe: Iron; Mn: Manganese; Zn: Zinc; B: Boron.

Conclusion

Cocoa produces fruits throughout the year, with one or two peak seasons. Variability exists for the pod and bean characteristics in different cocoa genotypes. Our study revealed significant variations among twenty cocoa genotypes for pod weight, husk weight, bean count per pod, fresh bean weight per pod, single dry bean weight, nib recovery, and shell percentage. Bean size is an economically important factor for the chocolate industry, and it was significantly associated with husk weight, pod weight, and nib recovery. The weight of the dry bean was found to be higher in pods with higher pod weight and husk weight. However, it decreased significantly with an increase in the bean count per pod. Higher nib recovery was closely associated with single dry bean weight. This indicates that small beans have a higher shell content and are more difficult for the industry to process. Leaf nutrient analysis has been widely used to indicate the nutritional status of cocoa trees. The studies on their relationship with leaf mineral nutrient status are very limited. Pearson’s correlation coefficients indicated that pod and bean characteristics in different genotypes had no significant association with leaf nutrient status. Even, the nutrient ratios had no tangible influence on the pod/bean traits, except for K/P and Ca/B, which had significant associations with the husk weight and pod count per tree, respectively.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors thank the Director of ICAR-Central Plantation Crops Research Institute, Kasaragod, India, and the Dean of Kittur Rani Channamma College of Horticulture, Arabhavi, India. This research received funding from the Indian Council of Agricultural Research (ICAR-CPCRI Institute Project Code no. 1000763058) and was a part of PhD research work of the first author.

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