Introduction
The Rubiaceae family incorporates the genus Coffea, which consists of 130 species (Davis and Rakotonasolo, Reference Davis and Rakotonasolo2021). Among them, two species, Coffea arabica L. (Arabic coffee) and Coffea canephora Pierre ex Froehner (Robusta coffee), are almost entirely responsible for the worldwide coffee trade (Cassamo et al., Reference Cassamo, Mangueze, Leitão, Pais, Moreira, Campa, Chiulele, Reis, Marques, Scotti-Campos, Lidon, Partelli, Ribeiro-Barros and Ramalho2022). These two species are currently cultivated in about 80 tropical countries, with Robusta coffee attaining an increasing importance, responsible for ca. 44% of world coffee production and trade ICO (International Coffee Organization, 2024). Coffea arabica is an allotetraploid self-compatible species, while C. canephora is an allogamous diploid, characterized by gametophytic self-incompatibility and synchronized flowering, mechanisms that naturally favour cross-pollination (Souza et al., Reference Souza, Rocha, Alves, Espíndula, Ramalho and Teixeira2017). The coffee berries start to develop just after flowering, which usually occurs after the first spring rains (Eira et al., Reference Eira, Silva, De Castro, Dussert, Walters, Bewley and Hilhorst2006). Due to successive blossoms, it is possible to find berries with varying degrees of maturation on the same branch during the harvest, compromising yield and quality (Miranda et al., Reference Miranda, Drumond and Ronchi2020).
Coffee tree phenology was first defined for C. arabica (Camargo and Camargo, Reference Camargo and Camargo2001; Pezzopane et al., Reference Pezzopane, Pedro Júnior, Thomaziello and Camargo2003) and adapted for C. canephora (Marcolan et al., Reference Marcolan, Ramalho, Mendes, Teixeira, Fernandes, Costa, Vieira Junior, Oliveira, Fernandes and Veneziano2009; Abreu et al., Reference Abreu, Roda, Krohling, Campostrini and Rakocevic2023), being considered to have six phases: (1) branch and flower bud induction and formation; (2) maturation of flower buds; (3) anthesis; (4) berry and leaf expansion; (5) berry maturation; and (6) winter resting phase. Additionally, the coffee berry maturation process has been subdivided into another five stages (Morais et al., Reference Morais, Caramori, Koguishi and Ribeiro2008), being M1 for green berries, that is, without evidence of colour change; M2 for cane green berries, which have already begun to ripen; M3 for berries in the ‘cherry’ stage, light red colour and physiologically ripe; M4 for berries in the ‘raisin’ stage (overripe), with a dark red colour and with the onset of dehydration; and M5 for dry berries, desiccated with dark external colouration. Coffee fruits turn red when mature or yellow in very few genotypes due to the replacement of chlorophyll in the exocarp by red (flavonoid) or yellow (xanthophylls) pigments (Castro and Marraccini, Reference Castro and Marraccini2006; Esquivel et al., Reference Esquivel, Viñas, Steingass, Gruschwitz, Guevara, Carle, Schweiggert and Jiménez2020). The berry colour is a good marker of maturation and is correlated with the development of high-quality flavours in the final coffee beverage after roasting (Amorim et al., Reference Amorim, Hovell, Pinto, Eberlin, Arruda, Pereira, Bizzo, Catharino, Morais Filho and Rezende2009).
The coffee berry is morphologically composed of the pericarp (i.e. exocarp, mesocarp, and endocarp), the perisperm, likewise called the spermoderm, and the bean (endosperm) that contains the embryo (Castro and Marraccini, Reference Castro and Marraccini2006). In each C. canephora berry, there are usually two seeds (beans), but there are cases where only one is observed (Hall et al., Reference Hall, Trevisan and de Vos2022). Coffee berries are usually harvested according to the colour of the berry’s pericarp. In the mature coffee fruit (drupe, also called coffee cherry or berry), the exocarp is red or yellow. To obtain the commercial coffee beans, the pericarp outer skin, pulp, pectic adhesive layer, and parchment (usually together with bean silverskin) are removed through either dry or wet processing (Kitzberger et al., Reference Kitzberger, Sorane, Pot, Marraccini, Protasio Pereira and Scholz2020).
Robusta coffee is almost entirely subjected to a drying process in Brazil, which is the cheapest way of transforming ripe berries into processed beans (Poltronieri and Rossi, Reference Poltronieri and Rossi2016). In this process, the berries are dried on terraces or using mechanical dryers, without the removal of the husk (pericarp), followed by the mechanical separation of the beans from husk and other impurities (Alves et al., Reference Alves, Isquierdo, Borém, Siqueira, Oliveira and Andrade2013; Pimenta et al., Reference Pimenta, Angélico and Chalfoun2018). This process needs to be conducted with caution, so as not to break the beans, as well as to prevent the mixture of clean beans with berries, husks, or fragments, which would impair their quality.
The fresh mass (FM) accumulation in C. arabica follows a double sigmoidal dynamics (Fernandes et al., Reference Fernandes, Pereira and Muniz2017). Throughout the whole berry formation process, the dry matter (DM) accumulation also follows a sigmoidal trend in C. arabica (Laviola et al., Reference Laviola, Martinez, Salomão, Cruz, Mendonça and Rosado2008) and C. canephora (Partelli et al., Reference Partelli, Espindula, Marré and Vieira2014; Covre et al., Reference Covre, Oliveira, Martins, Bonomo, Rodrigues, Tomaz, Vieira, Paye and Partelli2022), attaining the highest values in the M3 phase. DM accumulation dynamics of the main coffee berry components (beans and husks), as well as bean DM proportion during the maturation phase, can be used to predict the most adequate harvesting time, in order to ensure a high quality of yielded beans. However, there is still a knowledge gap regarding the dynamics of DM accumulation in the berry components throughout the maturation process. It had been hypothesized that (1) C. canephora genotypes may show different dynamics in DM accumulation throughout the maturation process – that is, the genotypes with a late maturation cycle would have a slower accumulation when compared to the early ones; (2) the highest berry and bean DM will be obtained when the berries reach full ripeness; and (3) the husk DM dynamics will compete with bean DM accumulation, with both processes showing different patterns. To test these hypotheses, this study evaluated the DM accumulation in berries, beans, and husks of six C. canephora genotypes along maturation, aiming at identifying the best moment for harvesting and obtaining the highest bean yield for each genotype.
Material and methods
Plant material and experimental design
The experiment was carried out in the experimental coffee plantations of the Federal University of Espírito Santo, São Mateus (18°40’23’’S, 39°51’22’’W, 36 m a.s.l.), Espírito Santo State, Brazil. The region’s climate is tropical, with dry winter and rainy summer, characterized as Aw according to Köppen’s classification (Alvares et al., Reference Alvares, Stape, Sentelhas, Gonçalves and Sparovek2013; Seki et al., Reference Seki, Tetto, Tres and Vieira2021). The soil was classified as a Yellow Dystrophic Argisol (EMBRAPA, 2013).
Five plants from each of six Coffea canephora genotypes (Pirata, Bamburral, A1, Clementino, Beira Rio 8, and P1) were used in this study. These genotypes belong to two cultivars, Andina and Tributun, both of which are widely cultivated and play an important role in enhancing productivity and adaptability across various coffee-growing regions (Partelli et al., Reference Partelli, Golynski, Ferreira, Martins, Mauri, Ramalho and Vieira2019; Reference Partelli, Giles, Oliosi, Covre, Ferreira and Rodrigues2020). Tributun was developed through a partnership among the Federal University of Espirito Santo (Brazil) and local coffee growers, reflecting a successful model of collaboration between researchers and producers. Andina is notable for being the first registered C. canephora cultivar recommended for cultivation at high altitudes with cooler climates. Of the six genotypes evaluated, A1 is the most commonly planted by Brazilian coffee farmers because of its superior agronomic traits and widespread acceptance.
The studied genotypes have different maturation cycles: Pirata, A1, and Beira Rio 8 are early/medium cycle; Bamburral and Clementino are medium; and P1 has a late cycle. They were propagated by cuttings and planted in the field in 2018, at a row spacing of 2 m and 1 m between two plants in the row, with a population of 5,000 plants ha−1. All plants were grown with the two orthotropic axes, resulting in 10,000 orthotropic axes ha−1. The experiment was conducted in 2020 when the coffee plantation was two years old.
Irrigation was based on a soil water balance method, with the reference evapotranspiration calculated according to the Penman–Monteith method (Allen et al., Reference Allen, Pereira, Raes and Smith1998). The drip irrigation hoses were located 5 cm away from the coffee trunks, following coffee rows, with emitters being spaced every metre. Nutritional and phytosanitary controls were carried out according to the crop needs and considering the phenological stages. Approximately 1.5 Mg ha−1 of lime was applied, following soil analysis recommendations, using the base saturation percentage, which is the total of the four exchangeable base cations (Ca2+, Mg2+, K+, and Na+) relative to the cation exchange capacity. Fertilization was carried out based on soil analysis and yield data, and a total of 500 kg N ha−1, 80 kg P2O5 ha−1, and 400 K2O kg ha−1 were applied, divided into six equal doses, with supplying done from flowering to early maturation phenophases. Ca and Mg were supplied through liming, while micronutrient levels were adjusted annually with applications of 2.0 kg Zn ha−1, 1.0 kg B ha−1, 2.0 kg Cu ha−1, and 10 kg Mn ha−1.
Berry sampling and post-harvesting processing
Berry sampling started at the end of the grain filling stage, ca. 33 weeks after flowering (WAF), and continued afterwards every 14 days until berry maturation of all six genotypes was completed. This procedure resulted in nine sampling dates (periods), the last one at 49 WAF. The berries were harvested manually from five plants of each genotype, from previously marked second-order plagiotropic axes localized in the medium third of the plant, one branch for each sampling.
Berries were sampled, counted, photographed, and weighed (fresh mass, FM), registering the mass in grams (scale precision of 1 mg). After that, the samples were dried in a ventilated oven at 50°C for seven days to achieve constant mass, or DM. The separation of the beans from the husk was performed manually. Dry beans were also photographed and weighed, while the husk mass was calculated from the difference between the dry berry and bean mass.
DM parameters were standardized for a single berry. Berry DM, DM of beans per berry, DM of the husk, and the proportion of beans and husk were calculated for each genotype. Subsequently, the berry FM to bean DM ratio was also calculated. The initial moisture content of the coffee berries was estimated by the difference between their FM and DM. To assess the distribution and efficiency of dry matter allocation within the fruit, three performance indicators were calculated according to the methodology proposed by Rakocevic et al. (Reference Rakocevic, dos Santos Scholz, Pazianotto, Matsunaga and Ramalho2023): (i) the proportion of bean dry matter relative to the berry dry matter (DM performance); (ii) the proportion of bean dry matter relative to the berry fresh mass (BDM performance); and (iii) the proportion of husk dry matter relative to the berry fresh mass (HDM performance). These metrics provided a comprehensive evaluation of the efficiency with which genotypes allocate biomass to economically valuable components.
Statistical analyses
Samples from all nine time observations were collected from the same five plants of each genotype, which were randomly distributed in the experimental field. Each plant was considered a repetition. R Core Team (2024) software was used for all statistical analyses. For the analysis of the dynamics of berry DM, bean DM per berry, husk DM per berry, and berry FM to bean DM ratio, an ANOVA with a double factorial scheme (fat2.crd) was performed, using the package ‘ExpDes’ (Ferreira et al., Reference Ferreira, Cavalcanti and Nogueira2014), after testing the hypothesis of variance homogeneity. Second-order polynomial regression models were fitted, considering six genotypes and nine sampling times. Tukey’s tests were used to compare the means of the genotype effects within all sampling times and the time effects within each genotype.
The data for percentage of beans and husks in berries was submitted to a two-way ANOVA (percentage of each component vs. sampling time), considering a mixed linear model (‘nlme’ package) and maximum likelihood to test the significance of differences between the accumulated mass of two berry parts (bean and husk) for each of the sampling times (33, 35, 37, 39, 41, 43, 45, 47, and 49 WAF). When presenting the bean and husk percentages based on berry dry matter, only the p-value for the interaction was considered, since the factors were not compared independently (Perecin and Cargnelutti Filho, Reference Perecin and Cargnelutti Filho2008; Tavares et al., Reference Tavares, Carvalho and Machado2016), trying to make the clearest possible presentation. Finally, yield parameters were submitted to one-way ANOVA, where multiple Tukey’s comparison tests were used to compare means among genotypes. All tests were performed for a 95% confidence level. The modelled mean, standard error (SE), and estimated p-values are shown in the figures and table.
Results
At 45 WAF, most of the berries had reached full ripeness, except for the P1 genotype, which required more time and reached full maturity at 49 WAF (Figure 1). Coffee beans showed visual modifications over the experimental period. Green berries usually had deformed and dark beans, while mature berries showed a lighter bean colour and fully formed beans, the latter with commercial acceptance. Berries needed a period of four to six weeks to complete at least 90% maturation, calculated from the beginning of the maturation stage (Figure 1). In genotypes with early/medium (Pirata, A1, and Beira Rio 8) and medium (Bamburral and Clementino) cycles, the change in exocarp colour initiated between 39 and 43 WAF, with most of them reaching full maturation by 45 and 47 WAF. The exocarp of the late cycle genotype P1 only turned red between 45 and 47 WAF, reaching full maturation at 49 WAF.
Visual evolution of berry maturation and dry beans of Coffea canephora genotypes Pirata, Bamburral, A1, Clementino, Beira Rio 8, and P1 sampled at the end of berry expansion to full maturation phenophase. The upper line of each genotype represents the fresh berries, while the lower line represents the dry beans.
The studied genotypes exhibited similar patterns of DM accumulation over the berry maturation process (Figure 2a). The highest berry DM investment rate was mostly observed between the end of leaf and berry expansion and the beginning of the maturation phenophase (33rd to 41st WAF). Afterwards and during the maturation phenophase, the rate of DM accumulation in berries was reduced, reaching stable DM values at the end of the maturation stage. Among the studied genotypes, Beira Rio 8 presented the greatest berry DM values throughout the experiment, varying between 291 and 542 mg berry-1, with an increase of 86% between 33 and 45 WAF (Figure 2a). By contrast, P1 showed the lowest berry DM during all nine sampling dates, presenting a difference of 278 mg berry-1 compared to Beira Rio 8 by the end of the experiment. The maximum berry DM values were found at the fully ripe stage, which differed in time among the six genotypes. This peak was attained by 45 WAF in Clementino and Beira Rio 8; by 47 WAF in Pirata, Bamburral, and A1; and by 49 WAF in P1, which was induced by differences in length of maturation cycles.
Berry (A) and bean (B) dry matter accumulation and second-order polynomial regressions for berry fresh mass to bean dry matter ratio (C) of Coffea canephora genotypes Pirata, Bamburral, A1, Clementino, Beira Rio 8, and P1. Berries were sampled from the end of the berry expansion phenophase to the full maturation phenophase (33–49 weeks after flowering). Letters compare genotype effects at each sampling time using Tukey’s test, while p-values marked in bold indicate significant differences (n = 5). Dashed lines, equations, and R2 represent polynomial regression adjusted to each genotype, which were graphically presented in colours to facilitate genotype differentiation. Black stars on the dashed lines represent the estimated points of maximum bean dry matter accumulation for each genotype.
Bean accumulation rate of DM per berry was higher during the pre-maturation period, starting from the end of berry expansion phenophase (33 WAF) up to 41 WAF, when the mean increase of bean DM per berry was above 70% in all genotypes (Figure 2b). The greatest values of bean DM per berry occurred when berries were fully ripe, between 43 and 47 WAF in early/medium and medium maturation cycle genotypes. Afterwards, the beans begin to lose weight until the end of the experimental period. Late maturation cycle genotype P1 had a different dynamic, with bean DM accumulation per berry continuously increasing until the last sampling. The evolution of DM accumulation in beans (Figure 2b) was very similar to DM accumulation in berries (Figure 2a). As for berry DM accumulation, Beira Rio 8 also had the greatest bean DM accumulation among the studied genotypes (Figure 2b). However, the difference in accumulated bean DM to the other genotypes was less expressive when compared to the differences in accumulated berry DM (Figure 2a). P1 showed lower bean mass than the other genotypes until the 41st WAF, but after that continued to gain weight until the last sampling. At this time, P1 presented higher bean weight than Pirata, A1, and Clementino (Figure 2b).
During a transient period between the leaf and berry expansion phenophase and maturation, husks showed low rates of DM increment (Figure 3), differing from bean DM accumulation (Figure 2). From 41 WAF (when the berry exocarp started to become red) and onwards, Beira Rio 8 exhibited significant increases in husk mass, up to maximal values at full maturation at 45 WAF (Figure 3). Similar husk DM dynamic patterns were observed in Bamburral, A1, Clementino, and Pirata, although with lower values than Beira Rio 8. In contrast, P1 did not show significant variations in husk DM accumulation during the experimental period, presenting the lowest values among all genotypes from 41 WAF onwards. That contrasted with the highest husk DM accumulation of Beira Rio 8, while the other genotypes showed intermediate values between these two genotypes (Figure 3). The greatest difference between genotypes occurred by 45 WAF, when Beira Rio 8 had a husk DM berry-1 about 156 mg higher than that of P1 (Figure 3).
Husk dry matter per berry in Coffea canephora genotypes Pirata, Bamburral, A1, Clementino, Beira Rio 8, and P1. Berries were sampled from the end of the berry expansion phenophase to the full maturation phenophase (33–49 weeks after flowering). Coloured bars represent the mean ± SE. P-values (n = 5) are marked in bold when significant. Lower-case letters compare the time effect within each genotype, while upper-case letters compare genotype effect for each sampling time using Tukey’s test.
The berry FM to bean DM ratio is considered an important index for determining bean yield, as a higher ratio indicates a greater number of fresh berries required to obtain a certain quantity of dry beans. P1 presented high values of the berry FM to bean DM ratios at the beginning of the berry harvest (33 WAF), which were gradually reduced during berry expansion and maturation up to 45 WAF (Figure 2c). Among all studied genotypes, the lowest berry FM to bean DM ratio was found in Clementino at 49 WAF, due to the presence of overripe berries (Figure 1). This resulted in a low ripe berry FM, and similar dynamics were observed in the A1 genotype.
Bean and husk percentages in berry DM did not follow the same pattern for the six genotypes over the experimental period (Figure 4). The highest values of bean percentage were obtained in the pre-maturation period, after the end of berry expansion. Among the genotypes, Bamburral and P1 had the highest percentage of beans in the berries, reaching 69% and 66% by 39 and 45 WAF, respectively. Pirata, Clementino, and Beira Rio 8 showed maximal values close to 60% between 37 and 41 WAF, both decreasing to ca. 50% by the last harvest. The genotype with the lowest performance when considering bean percentage over the experimental period was A1, with a husk content greater than 50% during the last samplings.
Bean and husk percentage in the dry matter of one berry of Coffea canephora genotypes Pirata, Bamburral, A1, Clementino, Beira Rio 8, and P1. Berries were sampled from the end of the berry expansion phenophase to the full maturation phenophase (33–49 weeks after flowering, as shown in the external radius of the chart). For each genotype, lower-case letters compare sampling time for each bean and husk percentage, while upper-case letters compare bean and husk percentage in each sampling time (Tukey’s test at 5% probability). P-values marked in bold indicate statistically significant interactions (n = 5).
The yield components (berry FM, berry DM, processed bean mass (BDM), and mass performances) significantly differed among the studied genotypes (Table 1). The highest FM, DM, BDM, and HDM were obtained in Beira Rio 8, while the lowest DM and HDM values were found in P1 and the lowest BDM in the A1 genotype. The initial berry moisture (field berry moisture) was around 60%, with A1 having the highest and Bamburral the lowest moisture. DM performance was the highest for P1 and Bamburral and lowest for A1, due to the high husk content per berry in this latter. P1 and Bamburral presented the highest values for DM and BDM performances and the lowest values for HDM performance.
Components of the berry and bean yields of six Coffea canephora genotypes: fresh berry mass (FM); berry dry matter (DM); bean dry matter (BDM) and husk dry matter (HDM); initial berry moisture (%); the ratio of bean dry matter to berry dry matter (DM performance); the ratio of bean dry matter to berry fresh mass (BDM performance); and the ratio of husk dry matter to berry fresh mass (HDM performance). Data refer to the sampling closest to the moment of the highest DM accumulation in beans (45 weeks after flowering [WAF] for Pirata, Bamburral, A1, Clementino, and Beira Rio 8 and 49 WAF for P1). In columns, means followed by the same letter did not differ significantly (Tukey test, n = 5)
Discussion
This novel study quantified and modelled traits related to dry matter accumulation of berry components (beans and husks) from the end of the leaf/berry expansion phenophase until full maturation and considered the colour of the exocarp in six genotypes of Coffea canephora in order to identify the best harvesting time for the highest bean yield, which was found to be genotype-dependent.
The change in berry colour in C. canephora was similar to that observed for C. arabica, in which the berry exocarp colour transitions from green–brown–red–deep red across four maturation stages are due to the external physical modifications related to the differential presence of up to 456 metabolites (Li et al., Reference Li, Zhou, Zheng, Zhao, Shen, Wang, Qiu and Fan2023). The correlation of DM dynamics to the berry exocarp colour provides a very practical reference to assist farmers’ decision-making regarding the ideal time to start berry harvesting (Figure 1), that is, using the change in the berry colour as a benchmark of the maturation process. In the berries of C. arabica cv. In Colombia, which displays an early maturation cycle, a large decrease in chlorophyll content is followed by a quick and sudden accumulation of berry anthocyanin (Marín-Lopez et al., Reference Marín-López, Arcila-Pulgarin, Montoya-Restrepo and Olivero-Tascón2003). In fact, it has been known for a long time that the complete change in the berry colour is the main visual criterion to identify berry maturity, although this is complicated by the absence of synchrony between the maturation of the exocarp – husk, and the endosperm – bean (Castro and Marraccini, 2005). Considering this at the molecular level, the gene expression of ubiquitin 40S protein S27a and vacuole invertase inhibitor shows significant downregulation along the maturation. In addition, proteins like E3 ubiquitin-ligase SHPRH, luminal-binding 5-like, and cinnamoyl-reductase 2-like decrease in abundance when comparing red and yellow berries, highlighting their major molecular changes during fruit maturation (Cheng et al., Reference Cheng, Furtado and Henry2018). The accumulation of DM in beans usually occurred earlier when compared to the husk, leading to a greater percentage of bean DM in the berry during the period preceding the pericarp colour change (Figure 4). This was clearly expressed in the early/medium genotype Pirata, which presented the highest bean percentage at 37–39 WAF and reached the red berry stage later on (43–45 WAF). However, the berry DM alone did not fully characterize the harvested commercial bean yield, as changes in berry DM had not followed the same trend as BDM (Table 1). This occurred due to the percentage of bean and husk DM in the berries, which varied among the genotypes according to the point of ripeness (Figure 4). Therefore, we proposed that it is important to consider berry DM and BDM performances in estimations of commercial coffee bean yield and genotype potential, as they assist in the estimation of the right moment for harvesting and would optimize bean yield by reducing losses.
During the drying process, the coffee berries lost about 60% of their FM in all studied genotypes. The water content in the fresh berries gradually decreased, and the lowest values were observed in fully mature fruits. The processed bean DM per berry represented only 23% of initial berry FM, with the highest value (24%) obtained at 49 WAF and the lowest one (16%) at 33 WAF. Berry DM accumulation increased as maturation progressed, peaking at 45 (Beira Rio 8 and Clementino), 47 (A1, Bamburral, and Pirata), and 49 WAF (P1). The increase in berry DM is mainly due to an increase in bean DM per berry, and it shows a steeper percentage of DM or accumulation of reserves during maturation when compared to the whole berry (Eira et al., Reference Eira, Silva, De Castro, Dussert, Walters, Bewley and Hilhorst2006).
Although acting as strong sinks (Alves et al., Reference Alves, Paglis, Livramento, Linhares, Becker and Mesquita2011), the dynamics of DM accumulation in beans and husks followed distinct patterns (Figures 2b and 3). The beans had a fast initial DM accumulation, and slight losses in DM occurred after reaching the maximum value at about 45 WAF (except for P1), as shown in Figures 2b and 3. Such reductions in DM are related to the bean metabolic reorganization process during maturation. Once the full maturation stage was reached, slight decreases in bean DM per berry can be explained by an interruption of the translocation of photoassimilates from the berry to the bean, as well as by substrate consumption in respiration during the final maturation stages (Carvalho and Nakagawa, Reference Carvalho and Nakagawa1980; Eira et al., Reference Eira, Silva, De Castro, Dussert, Walters, Bewley and Hilhorst2006; Pérez et al., 2023). Respiration provides ATP for sustaining metabolic processes related to costly secondary metabolite production in beans, namely, a range of phenolic components with protective roles in plants (Farah and Donangelo, Reference Farah and Donangelo2006; Li et al., Reference Li, Zhou, Zheng, Zhao, Shen, Wang, Qiu and Fan2023).
The husk DM accumulation pattern differed from that of bean DM accumulation, being stable at the beginning and reaching the highest values at the end of the experiment, when the berries were fully ripe (Figure 3). This late investment in husk DM during berry maturation likely has a protective role against predators and diseases (Carrera-Castaño et al., Reference Carrera-Castaño, Calleja-Cabrera, Pernas, Gómez and Oñate-Sánchez2020). Husks are considered a residual product of coffee processing by many coffee producers, but due to their high mineral content (P, N, and Ca) (Covre et al., Reference Covre, Rodrigues, Duarte, Braun, Ramalho and Partelli2016), their use as fertilizers can reduce the need for mineral fertilizer in coffee plantations, making the plantations more economically and environmentally sustainable.
The final stage of maturation visually presented some overripe berries (Figure 1), which might reduce the quality of coffee beverages (Martínez et al., Reference Martínez, Aristinzábal and Moreno2017). Overripe berries were notably present in this study during the late samplings of the A1 and Clementino genotypes (early/medium and medium maturation cycles, respectively), whereas the opposite was found for P1 (late maturation genotype). The reduced water content in overripe berries might additionally lead to mechanical problems during berry processing, resulting in an increased percentage of broken beans and low coffee quality (Osorio Pérez et al., Reference Osorio Pérez, Matallana Pérez, Fernandez-Alduenda, Alvarez Barreto, Gallego Agudelo and Montoya Restrepo2023). The maturity stages do not always show differences in terms of chemical components, and only fructose and glucose contents have increased values at more developed stages (Osorio Pérez et al., Reference Osorio Pérez, Matallana Pérez, Fernandez-Alduenda, Alvarez Barreto, Gallego Agudelo and Montoya Restrepo2023). Defective coffee beans represent about 15%–20% of coffee production on a weight basis, being rejected as undesirable for good beverages (Ramalakshmi et al., Reference Ramalakshmi, Kubra and Rao2007; Worku et al., Reference Worku, Astatkie and Boeckx2022). Therefore, there are losses in the quality and final quantity of coffee when harvesting after the ideal time. Interestingly, chlorogenic acids, which are characterized by their antioxidant activity, are found to be present in similar amounts in defective coffee as in high-quality beans, potentially indicating triage of berries and beans in conserving food systems (Ramalakshmi et al., Reference Ramalakshmi, Kubra and Rao2007).
From the point of view of final coffee bean quality, the objective is to ensure the harvest of beans of the highest quality (even if they have lowered DM), otherwise there is a risk of high DM production, without quality (Haile and Kang, Reference Haile, Kang and Castanheira2020). The optimum moment of berry harvest was when the highest bean DM per berry was attained, which was between 43 and 47 WAF for the genotypes studied here, a period in which the berry FM to bean DM ratio was the lowest (Figure 2c). The average increase in bean DM per berry was about 15% for all studied genotypes between 41 and 45 WAF (Figure 2b). Forty-five WAF was the best stage for berry harvest of C. canephora in our experimental conditions, with the exception of Pirata (47 WAF) and P1 (49 WAF) (Figure 2b). The proportion of beans and husks in the DM of the berry (Figure 2c) indicated that it can be considered as an index for characterizing superior coffee genotypes, together with high bean yield.
Considering only the fully ripe berries, Pirata, A1, Clementino, and Beira Rio 8 genotypes had elevated DM performances (∼50%), while P1 (late maturation cycle) and Bamburral (medium cycle) presented even higher values, above 60%, similar to that already shown by the percentage of beans in berries (Partelli et al., Reference Partelli, Oliosi, Dalazen, da Silva, Vieira and Espindula2021). Although self-incompatibility is an important trait for C. canephora plant populations, this trait should be managed to avoid a reduction in the efficiency of flower pollination, which affects yield in coffee fields (Depolo et al., Reference Depolo, Rocha, Souza, Santos, Espindula and Teixeira2022).
Conclusions
Second-order polynomial regressions were fitted for berry and bean DM accumulation over the maturation period. The dynamics of DM accumulation in berries, beans, and husks were influenced by the genotype maturation process, differing among classes of maturation. The DM accumulation in berries increased as the maturation progressed, attaining the highest values in the final weeks of the maturation process: 45–47 WAF for Beira Rio 8, A1, Pirata Bamburral, and Clementino (early/medium and medium maturation cycle genotypes) and 49 WAF for the late maturation P1 genotype. DM accumulation was initially the highest for berry and bean DM per berry (33–41 WAF), while the highest increases in husk DM accumulation occurred in the latter stages of maturation (41–49 WAF). High values for late husk DM accumulation could be related to embryo protection, which needs further research. The Beira Rio 8 genotype presented the highest DM accumulation in berries, beans, and husks. Bamburral and P1 showed the lowest berry FM to bean DM ratios, while A1 showed the highest berry FM to bean DM ratio, being a genotype with the lowest DM and BDM performance and bean yield. To obtain a higher bean yield, the indicated harvesting period for the genotypes Pirata, Bamburral, A1, Clementino, and Beira Rio 8 was between 43 and 47 WAF, while for P1 only at 49 WAF, when more than 90% of the berries were mature.
Not only should the absolute berry and bean yield be considered for high-productive genotypes, but also bean DM performance needs to be included in the characterization of commercial yields and selection of the high-quality genotypes. This means that the bean and husk proportions in berry DM should be identified as an index for characterizing superior genotypes. Considering that DM accumulation and bean yield were influenced by the genotype maturation cycles, a crop organization in rows/blocks taking into account the maturation cycle could be recommended, starting with the early cycle genotypes and ending with the late cycle ones, thereby facilitating the manual or semi-mechanized harvesting operations/management. Such agronomic procedures allow planned improvements in the quality and quantity of coffee beans produced by farmers.
Data availability statement
The raw data supporting the conclusions of this article will be made available by the authors on request.
Acknowledgements
The authors appreciated the support provided by Guilherme Aguiar Krohling for his help in the sample collection and the Federal University of Espírito Santo (UFES) for all the support provided for the research.
Author contributions
HPS: Investigation, data curation, formal analysis, validation, and writing – original draft; JNS: Validation and writing – review & editing; MR: Methodology, formal analysis, validation, and writing – review & editing; JCR: Validation and writing – review & editing; FLP: Conceptualization, funding acquisition, supervision, and validation. All authors have read and agreed with the actual version of the manuscript.
Funding statement
This work was supported by the Fundação de Amparo à Pesquisa e Inovação do Espírito Santo - FAPES (Proc. 2022-WTZQP for FLP, Proc. 2022-M465D for MR, and Proc. 2021-5THCJ with grant number 085/2022 for HPS) and Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq (Proc. 309535/2021-2 for FLP). Support from Fundação para a Ciência e a Tecnologia I.P., Portugal, through the units CEF (UID/04129/2020, https://doi.org/10.54499/UIDB/00239/2020), GeoBioTec (UIDP/04035/2020), and the Associate Laboratory TERRA (LA/P/0092/2020) to JCR is also greatly acknowledged.
Competing interests
The authors declare no conflicts of interest.
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