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Article

Morphological, Sensorial and Chemical Characterization of Chilli Peppers (Capsicum spp.) from the CATIE Genebank

1
INIAP, Estación Experimental Central de la Amazonía, Vía Sacha San Carlos km 3 de la Entrada a la Parker, Escuela Superior Politécnica del Chimborazo, Extensión Norte Amazónica, Orellana 170518, Ecuador
2
INIAP, Estación Experimental Santa Catalina, Panamericana sur km 1, Quito 170401, Ecuador
3
Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Sobi/Plen-KU, Thorvaldsensvej 40, 3, DK-1871 Frederiksberg C, Denmark
*
Author to whom correspondence should be addressed.
Agronomy 2020, 10(11), 1732; https://doi.org/10.3390/agronomy10111732
Submission received: 17 September 2020 / Revised: 22 October 2020 / Accepted: 29 October 2020 / Published: 6 November 2020
(This article belongs to the Special Issue Analysis of Crop Genetic and Germplasm Diversity)

Abstract

:
In order to assess the potential of 192 accessions of Capsicum L., from 21 countries, a morphological and agronomic characterization was carried out by applying 57 qualitative and quantitative descriptors. Multivariate analyses identified two large groups: the first including C. annuum (G3, G5, G7 and G8) and the second C. frutescens, C. baccatum, C. chinense and C. pubescens (G1, G2, G4, G6 and G9). The discriminant qualitative descriptors were the colour of the corolla, the colour of the anthers and position of the flower. The quantitative discriminant characteristics were length, weight and width of the fruit. The participatory selection identified 15 materials by colour, aroma, texture, flavour, size and thickness of fruits. Chemical analyses determined the highest concentration of flavonoids in the accessions 10,757 (16.64 mg/g) and 15,661 (15.77 mg/g). Accessions 17,750 (11.68 mg/g) and 10,757 (11.41 mg/g) presented the highest polyphenol contents. The highest capsaicin concentration was recorded in accessions 16,209 (55.90 mg/g) and 10,757 (48.80 mg/g). The highest antioxidant value was recorded in accessions 17,750 (90.85 mg/g) and 15,661 (87.03 mg/g). All these characteristics are important with a view to increasing industrial use and genetic improvement processes. These results show the existence of significant genetic variability within the genus Capsicum.

1. Introduction

Chilli pepper (Capsicum L.) is one of the most important spice and vegetable crops in the world in agricultural, cultural and economic terms [1,2,3]. The genus Capsicum, native to Tropical America, comprises 27 species [4,5]. The five most widely used species worldwide are: C. annuum L., C. chinense Jacq., C. frutescens L., C. baccatum L. and C. pubescens Ruíz & Pav. [6]. Capsicum annuum and C. frutescens—which according to The Plant List [7] are considered conspecific, but which are here maintained as separate taxa as they are in The Tropical Agricultural Research and Higher Education Center (CATIE) genebank—are known to have been domesticated in Mesoamerica [5], however the original description of C. frutescens by Linneaus was based on a cultivated specimen from India. In the Andean region, chilli peppers have been consumed for more than 5000 years; C. baccatum, C. pubescens and C. chinense are believed to be native to South America. Capsicum chinense was domesticated in the tropical lowlands; while C. baccatum possibly was domesticated in the valleys of Bolivia, while the domestication site for C. pubescens, which is a tall chilli, remains unknown [8,9]. Although Ecuador has not been considered a centre of origin of the species, archaeological Capsicum starches have been found that date back to 6250 years before our era [10].
The five cultivated species are diploid and self-compatible and the number of chromosomes of the species is 2n = 24 [11]. Cross-pollination rate among Capsicum spp. is highly variable, ranging from 2 to 90% [12]. The species C. annuum, C. chinense and C. frutescens, form a morphological complex of overlapping characters from a common base of genes; qualitative characters, such as floral characteristics, differentiate the three species morphologically. These are solitary flowers, creamy white in C. annuum; the C. chinense species presents two or three flowers per leaf node of a whitish-green colour and with a constriction at the base of the calyx at the junction with the pedicel; while the C. frutescens species presents an erect white-green flower without calyx constriction. The other species are relatively easy to distinguish: Capsicum baccatum has yellow or white-yellow flowers with greenish spots towards the basal part of the petals and C. pubescens has either uniformly purple or purple flowers with a white base and black-rough seeds [13,14].
To promote the use of germplasm collections, morphological characterizations are performed to describe the existing genetic diversity, as an example, intraspecific diversity studies for C. annuum in Mexico [15] and in India [16,17] are cited. Morphological characterization has allowed identifying intra and inter-specific variability in the case of Capsicum [18,19,20,21,22], identifying resistance to pathogens such as Phytophthora capsici [23] or insects such as the Bemisia tabaci Begomo-virus complex [24]. A combination of morphological and molecular descriptors was used in India by Yumnam et al. [25].
The objectives of this study were: (a) to determine the level of morphological diversity present in 192 accessions of Capsicum; (b) to identify the qualitative and quantitative characters with high discriminating capacity; (c) to classify Capsicum species into groups based on their quantitative and qualitative characteristics; (d) to identify germplasm through participatory sensory evaluation; and (e) to determine the chemical characteristics of promising materials.
Note: For abstract in Spanish, see Appendix A.

2. Methodology

2.1. Morphological Characterization

The morphological characterization was set up in a field experiment at CATIE location, in Turrialba, Costa Rica (9° 54′ North Latitude, 83° 40′ West Longitude, altitude 625 m a.s.l.). The average annual precipitation is 2700 mm, and the annual average temperature is 22 °C according to CATIE [Centro Agronómico de Investigación y Enseñanza Tropical, CR] [26]. For morphological characterization, we worked with 192 accessions of chilli (Capsicum spp.). These accessions come from various collections carried out in Central America and Mexico between 1976 and 2006 and germplasm exchanges carried out between institutions from five continents corresponding to 21 countries (Table 1).
Twenty plants per accession were installed in the field and the middle 10 evaluated (to eliminate border effect). The descriptors jointly defined by IPGRI [International for Plant Genetic Resources Institute, now BIOVERSITY, AVRDC and CATIE [27] were used, which comprise 57 qualitative and quantitative descriptors (Table 2 and Table 3). The data obtained from the morphological characterization were analysed using the InfoStat/Professional program version 2011 [28].
Qualitative and quantitative variables were used in a hierarchical cluster by using Ward’s method and Gower distance, also, contingency tables were used, using Chi-square, and multiple correspondence analyses were made.

2.2. Participatory Sensory Evaluation

For this stage the 192 morphologically characterized accessions were evaluated by 50 invited untrained participants representing producers, industrialists, chefs, scientists and ordinary consumers from Costa Rica, Mexico, Colombia, Ecuador and Peru. The evaluation was carried out in four phases. In the first phase, farmers/producers were invited to the field trial in CATIE to select accessions based on criteria such as colour, shape, size and production. In the second phase, with previously selected accessions, participants made a second evaluation related to shape, colour and size of the fruit. In the third phase, a sensory evaluation was carried out using the 9-point hedonic test proposed by Lawless [29]. However, this scale caused confusion for the attendees, so we decided to change to a friendlier scale, in which six criteria were recorded colour, smell, texture, flavour, size and thickness of the pulp. Each criterion was evaluated based on a 5-point scale: Excellent 5; Very Good 4; Good 3; Regular 2; Bad 1, proposed by Hernández [30]. In the fourth phase, the samples were tasted to determine the degree of fruit spiciness as reported by Hernández [30], the following scale was used: Very spicy 3, Medium spicy 2 and Regular 1. In each scale the assistants marked with an X the criterion they considered adequate based on their preferences. For the analysis of the results, frequency tables were prepared.

2.3. Chemical Characterization

The chemical analysis of the samples was carried out on the best 15 accessions selected by the morphological characterization and the participatory process. One kilogram of fruits, at the same maturity state, was harvested per accession from different parts of the plants to avoid differences in biochemical properties due to plant position according to Zewdie et al. [31]; Kirschbaum-Titze et al. [32]; Mueller-Seitz [33]. These samples were dried out in oven at 60 °C for 30 h, after which 100 g per accession were sent for analysis. The determination of flavonoid content was conducted using the method proposed by Miean and Mohamed [34]. The determination of antioxidant activity was completed using the method of measurement of the absorption capacity of oxygen radicals proposed by Álvarez-Parrilla et al. [35]. The determination of the content of total phenolic compounds was done according to the method proposed by Blainski et al. [36]. The determination of the concentration of capsaicin and dihydrocapsaicin was completed according to the method proposed by Juangsamoot et al. [37]. Finally, the analysis of the results was carried out through multivariate descriptive statistics.

3. Results

3.1. Descriptive Analysis of Morphological Characters

Evaluation of the characteristics of stem, leaves, flowers and fruits from 192 accessions are summarized follow.

3.2. Stem

The purple hypocotyl character was present in 70 accessions, purple stem in 5 accessions, purple knot anthocyanin in 78 accessions, light purple anthocyanin in 46 accessions and dark purple in one accession. Having accessions with purple characteristics determines the presence of anthocyanins, which are classified as nutraceuticals and appetizing agents. Bhattacharya et al. [38] indicate that anthocyanins minimize the proliferation of cancer cells, prevent lipid damage in food and protect against diseases of the heart. Likewise, Rodríguez and Kimura [39] mention that antioxidants can neutralize or reduce the activity of free radicals, associated with cardiovascular diseases.

3.3. Leaves

The variable leaf shape of the individual cotyledon was recorded according to the lanceolate, elongated-deltoid and oval categories, where the oval category was the most dominant since it was found in 134 accessions, corresponding to 69.79% of the materials evaluated. Likewise, the colour of the mature leaf was mostly green in 159 accessions corresponding to 82.81%. The majority of our accessions (170) had reduced leaf pubescence corresponding to 88.54%. This is in agreement with the results reported by Smith and Heiser [40] who mention that for C. frutescens leaf pubescence tends to be scarce.

3.4. Flowers

The colour of the corolla, the colour of the anther, position of the flower, the length of the placenta, and the pubescence of the stem had a marked influence on the discrimination of species. To the extent that the C. annuum were characterized by presenting white flowers and a single flower per leaf axil and C. frutescens presented a greenish-yellow flower without calyx constriction. It is worth noting that in our study the length of the ovary influenced the grouping of the samples, which differs from IPGRI [27], which do not consider it as highly discriminating for species differentiation. According to Sreelathakumary and Rajamony [41], the length of the ovary is correlated with the size and weight of the fruits and the most extended shelf-life at the market. This descriptor is more significant in C. frutescens than in C. annuum, and capsaicin is stored in it, also, both weight and size influence good filling of fruit cavities and seed production.
In the same way, this study agrees with the results reported by Hernández et al. [42] who mention that the characteristics of the flowers per leaf axil are an important variable to establish differences between the C. annuum and C. frutescens species. Note that the two taxa here are treated as separate taxa, though taxonomists in general consider them as being conspecific, as already mentioned; however, for practical reasons they are here considered as representing separate cultivar groups. Capsicum annuum accessions were characterized by having solitary flowers and C. frutescens for presenting more than one flower per leaf axil. The white colour of the corolla appeared in 47.40% of the accessions evaluated mainly in the G3 and G7, represented by the C. annuum species. The corolla’s greenish-yellow colour appeared in 36.46% of the accessions, specifically in the G4, G9 and G6 constituted by the species C. frutescens. In comparison, the colour of the corolla was light yellow at 7.29%, and in G1 mainly made up of the C. baccatum species (Figure 1). The above agrees with Pickersgill [43], who mentions that in Capsicum, two groups of flowers are defined: white and purple. In the group of white flowers, there are two subgroups, the one made up of C. baccatum and a second that groups C. annuum, C. chinense, C. frutescens. The group of purple flowers are the species C. eximium Hunz., C. cardenasii Heiser & P.G.Sm., and C. pubescens. On the other hand, Smith and Heiser [35] reported that in C. frutescens, the flowers are greenish-yellow, and for C. annuum, they are white.

3.5. Fruits

According to Andrews [43], the accessions belonging to the C. annuum species are characterized by having small, ovoid fruits with two locules, the fruit—a bloated berry—with different colours, e.g., light green, green, purple, yellow, orange and deep red. The C. frutescens species is characterized by presenting elongated fruits ending in a blunt point, with two locules per fruit, which agrees with the results found in this work where most of the accessions belong to C. frutescens and C. annuum.
In the characterized accessions, the following high variation coefficients were registered for the fruit characteristics:
  • anthocyanin spots or streaks on the fruit,
  • colour of the fruit in the intermediate state,
  • colour of the fruit in the mature state,
  • the shape of the fruit,
  • the shape of the fruit at the attachment of the pedicel,
  • fruit apex shape,
  • fruit appendix,
  • traces of petals and anthers,
  • fruit transverse ridges,
  • type of fruit epidermis,
  • pedicel persistence with fruit,
  • pedicel persistence with stem,
  • seed colour
  • seed surface.
These characters indicate the importance of the descriptor to discriminate variability within a collection. The results corroborate those reported by Smith and Heiser [40,44] who maintain that in each species of chilli pepper there are various fruit shapes and colour of immature fruits. In the accessions evaluated, the shape of the fruit was mostly triangular and elongated; however, small-fruited species tended to be round and conical, especially sweet pepper species. The variability of the genus is mainly due to the characteristics of the fruit, followed by the architecture of the plant, flower structure and the number of flowers per leaf axil [16].
Pickersgill [45] mentions that in Capsicum, the annular constriction of the calyx is characteristic of C. chinense and is absent in the other four species. For the colour of the immature fruits, it is typical for the fruits among the Capsicum spp. to start with a green colour before reaching the final colour at full maturity; however, the fruits in a mature state have mostly red tones and an elongated shape, while C. chinense matures with fruit shades of yellow and orange. Yellow colours of fruits in the intermediate maturity stage, i.e., apparent from the results obtained, were recorded in some accessions of both C. chinense (7300, 12,154, 5489), and C. frutescens (10,946, 10,793, 165,654). Furthermore, the shape of the fruit apex was mostly pointed in the accessions studied and the epidermis of the fruit was smooth, i.e., characteristics that correspond to the C. frutescens and C. annuum species.

3.6. Grouping of Accessions Based on Morphological Variables

The hierarchical cluster, using the qualitative and quantitative variables identified significant differences among nine accession groups of Capsicum spp. Significance (p < 0.0001) was obtained employing a multivariate analysis and the differences between mean vectors were obtained using the Hotelling comparison test corrected by Bonferroni [46,47].

3.7. Combined Analysis of Qualitative and Quantitative Variables

The result of the grouping of the accessions—obtained with the Ward method and the Gower distance—allowed us to identify the taxonomic structure of the collection, where the relationship between the groupings could be seen, i.e., C. annuum (groups 7, 8, 5 and 3), C. frutescens (groups 9, 6, 4 and 2). However, within these groups there are also accessions of C. chinense and C. pubescens and group 1 formed by the C. baccatum species. Group 3 contains the highest number of accessions (36); while Group 1 is made up of nine accessions. The groups with the highest similarity for the qualitative and quantitative variables are Group 1 and Group 2 (Table 4, Figure 1).

3.8. Discriminant Values

Regarding the qualitative descriptors, from the 39 characters analysed using the X2 test, 30 of them were identified with high significance (p < 0.0001) (**), and nine were not significant (ns). These results indicated the presence of a large number of descriptors making an essential contribution to separate the nine genetic groups (Table 5), moreover they presented high association coefficients. Likewise, 15 characters with the highest discriminant value were recorded, which can be used to establish genetic differences between groups.
The colour of the corolla and the colour of the anthers were the characters with the highest discriminant value (325.34 and 323.7 respectively) and presented the highest association coefficients. The position of the flower presented an X2 value of 166.04 and the highest value according to the Cramer test (0.54); therefore, it has a high contribution to discriminate between genetic groups, as has the colour of the corolla that also provides a discriminating value. These results indicate that the G4 and G9 groups are associated with the white character of the corolla.
Regarding the quantitative descriptors, six were identified with the highest discriminant value: leaf length/width ratio, width mature leaf, fruit length, fruit width, fruit wall thickness, plant height; these descriptors allowed to differentiate the nine groups (Table 6). In addition, we determined that accessions within the groups maintain a close relationship, once there is not much variation since they present small values of standard deviation.
The discriminant analysis found less distance between the species of C. annuum, C. frutescens and C. chinense. These three taxa are separated from C. baccatum and C. pubescens, because these two species grow in highlands (2800 m a.s.l.), where the climatic conditions differ from the low altitudes (200 m a.s.l.) where C. pubescens is distributed through the middle region of the Andes mountain range (1300 m a.s.l.). Capsicum baccatum is widely distributed throughout the lowlands of South America, as mentioned by Pickersgill [43]. The studies by García [48] corroborate the previous results; García [48] points out that the morphological characterization did not allow the species of C. annuum, C. chinense and C. frutescens to be differentiated. These observations are in agreement with Pardey et al. [18] who concluded that the species C. annuum, C. chinense and C. frutescens make up the same morphological group; like Vallejo et al. [49] who managed to discriminate the C. pubescens and C. baccatum species, but were unable to discriminate C. annuum, C. frutescens, C. chinense.
The Capsicum population presented morphological variation in the qualitative characteristics of the C. annuum, C. chinense and C. frutescens species because of the shared morphological features among the three species, making taxonomic classification difficult. This agrees with the results of García [48] and Palacios [50] who confirm this intraspecific variability; they also mention that as a result of the morphological description, it could be assumed that the three taxa constitute the same group. Similarly, the studies by Vallejo et al. [49], and Palacios Castro and García [51] managed to discriminate the species of C. pubescens and C. baccatum, but not between the species C. annuum, C. frutescens and C. chinense. The results of this study continue to corroborate the hypothesis that these three species are a large group in the process of differentiation, which is consistent with the studies conducted by Pickersgill [52].
The results of the present study are in agreement with those by Chávez-Servia [53] and Chávez-Servia and Castillo [54], who reported that variables such as length, width and shape of the Capsicum fruit showed considerable genetic variation. The purple colour of the anther was observed in the C. chinense species; while C. baccatum anthers presented a yellow colouration. On the other hand, C. annuum had pale blue anthers and C. frutescens blue. The species tended to have no stain on the corolla, except for C. baccatum, which is the typical characteristic of this species. The flowers in C. frutescens are erect; while in C. annuum and C. chinense the position of the flowers varied between intermediate and/or hanging.
According to Martín and González [55] and Fernández [56], chilli peppers with large-sized fruits and a thick epidermis tend to be less pungent. In contrast, in the accessions with smaller fruits where also the epidermis is thinner, the concentration of capsaicinoids increases, which is consistent with the results of the investigation, here accession 16,209 presented higher capsaicin content (5590 ug/g), while accession 16,450 registered low capsaicin content (200 ug/g).

3.9. Participatory Sensory Evaluation

The 50 people attending the workshop represented the following categories: producers (30), industry (5), chefs (4), scientists (5) and people who like to consume chilli (6). In the first phase, 134 accessions were selected as ‘Very Good’, presenting characteristics such as fruits with characteristics such as colour (pale orange, red, dark red and orange), shape (bell-shaped, triangular, elongated, bell-shaped and thick), size (medium and large) and fruit production. In the second phase, participants chose 64 accessions using the shape, colour and size of the fruit as selection criteria. In the third phase, 34 samples were selected with the criteria: taste, odour, texture, pulp thickness and size (Appendix B, Table A1); and, in the fourth phase, the most relevant fruits with orange, pale orange and red epidermis colours were selected. The shapes of the fruit are bell-shaped, and triangular, or bell-shaped and thick; the epidermis are of the fruit is semi-wrinkled and rough and fruits of medium to large size.
At the end of the process, the samples of the accessions were rated as follows:
  • As excellent—accession 15,661 (dark red fruit colour, bell-shaped and thick shape, large size)
  • As very good—accession 7818 (dark red fruit colour, triangular shape, medium size)
  • As good—accessions 16,304 (red fruit colour, flared shape, large size), 10,757 and 22,119 (red fruit colour, flared shape and compact, small size), 9892 (red fruit colour, flared shape, medium size), 9916 and 17,750 (orange fruit colour, bell-shaped, large size), 8994 and 16,209 (red fruit colour, triangular shape, medium size), 17,268 and 9902 (red fruit colour, bell-shaped, medium size).

3.10. Chemical Characterization

The nutritional value was determined in 15 accessions, selected as promising in morphological characterization, corresponding to the taxa C. annuum, C. chinense, C. frutescens, C. baccatum and Capsicum spp. Furthermore, these accessions were rated as excellent in the participatory selection. The accessions that had the highest concentration of capsaicin (5.59 mg/g), polyphenol (18.68 mg/g) and flavonoid (16.64 mg/g) were 16,209, 17,750 and 10,757, respectively (Table 7). The content of total polyphenols, flavonoids and capsaicinoids varied in the accessions evaluated, with a tendency to present an association with the morphological classification described by Morán et al. [57]. Appedino [58] studied 13 cultivars of C. annuum, finding concentration levels of flavonoids (0.028 and 0.551 mg/g) lower than those found in the accessions in the present study.
The results in Table 7 coincide with those found by Cázares et al. [59], who report that the populations of Ma’x ik and Sukurre belonging to the C. chinense species presented the highest capsaicin values (2.93 and 4.35 mg/g); while the lowest values reported for C. annuum sweet pepper populations (0.20 mg/g).
Additionally, Antonious and Jarret [60] studied different species of Capsicum, finding low concentration levels of capsaicin (0.0009 to 0.002 mg/g). Estrada et al. [61] reported increasing levels of capsaicinoids as maturation progresses, finding total capsaicinoid concentrations of between 0.15 to 0.70 mg/g (ps). However, these values are lower than those reported in the accessions studied here, where values between 5.59 to 0.20 mg/g were found (Table 8).
The Biplot from the principal component analysis of the 15 selected accessions shows the first two principal components explaining variance greater than 92% (Figure 2). The contents of polyphenols, antioxidants and flavonoids are highly correlated with each other and these in turn are correlated with humidity. In the case of capsaicin, its content is independent of the amounts of polyphenols, antioxidants and flavonoids.
Accessions 17,750, 10,757, 9892 and 15,661 are those with the highest amount of polyphenols, antioxidants and flavonoids, in turn these four accessions together with accessions 16,209 and 17,262 were the ones that obtained the highest score in the selection made by the producers. Accessions 17,750, 10,757 contain the most capsaicin content, being only surpassed by accession 16,209. On the opposite side, accession 16,450 is the one with the least content of nutritional values and in turn has a low capsaicin content
Of the four selected accessions with the best nutritional content, two of them belong to the genus C. chinense (17,750 and 10,757) and the accession (15,661) belongs to the genus C. annuum, accession 9892 belongs to C. frutescens. Regarding the classification by conglomerates, these four accessions belong to groups G2, G3 and G9. The highest capsaicin content was recorded in accession 16,209 belonging to the species C. baccatum.

4. Discussion and Conclusions

The most discriminant qualitative characteristics were colour of the corolla, the colour of the anthers and position of the flower; while the most discriminant quantitative characteristics were leaf length/width ratio, width mature leaf, fruit length, fruit width, fruit wall thickness and plant height. This is similar to previous studies by Medina et al. [62], Pardey et al. [18] Ortiz et al. [20] and Castañón et al. [63] who have also identified colour of the corolla, corollar spot colour, fruit width and fruit length as discriminant variables within other Capsicum spp. collections. A practical morphological characteristic found in our C. annuum and C. frutescens accessions is the persistence of the pedicel with the fruit, According to Sreelathakumary et al. [41] this characteristic, along with the length of the placenta, is correlated with the mass of the fruits and, therefore, longer shelf life.
The agronomic characterization allowed classifying the genetic variability of the Capsicum germplasm collection into two large groups and nine subgroups. The two large groups are formed by the subgroups G7, G8, G5 and G3 represented by C. annuum, and the second group formed by subgroups G4, G9, G6, G2 having mostly C. frutescens accessions plus G1, represented mainly by C. baccatum. Subgroup 1 (G1) differentiates from the other subgroups because of the presence of spots on the corolla (Corollar spot colour) similarly observed by García [48], Palacios & García [51]. and Walsh & Hoot [64]. It is important to notice that within all subgroups (except G8) there are few intercalated accessions of C. baccatum, C. pubescens, C. chinense and C. spp. (Table 4). Capsicum phylogeny determined closer relation among C. annuum, C. frutescens and C. chinense which is known as C. annuum complex Pickersgill, [43], Vallejo et al. [49], Pardey et al. [18] and Palacios and García [51].
The description of CATIE’s Capsicum spp. international collection permitted to identify promising materials e.g., after the morphological and participatory characterization, the following accessions were identified as promising: C. chinense—10,757 and 17,750; C. frutescens—9892; C. annuum—15,661 and 7816; and C. baccatum—16,209. Also, four accessions were selected with the highest chemical concentration (polyphenols, flavonoids, and capsaicinoids), two of them belong to the species C. chinense (17,750 and 10,757), the accession (15,661) belongs to C. annuum, and accession 9892 is referred to C. frutescens. These selected materials or the collection as a whole could be used by interested scientist as well as farmers.

Author Contributions

N.J.P.A. was responsible for the conceptualization, data curation, analyses and methodology, A.M.-A. and C.G.T.B. contributed further analyses and writing, M.S. contributed to the translation, writing and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded exclusively by Instituto National de Investigaciones Agropecuarias INIAP [the Ecuadorian National Institute of Agricultural Research].

Acknowledgments

The authors express their gratitude to the Tropical Agricultural Research and Training Center CATIE, for allowing the research to be completed at the Genebank and, in turn, to the entire technical, field and teaching team that supported the execution. The National Institute of Agricultural Research (INIAP) is gratefully acknowledged for providing the funding to make the research possible.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Resumen
Con el objetivo de evaluar las potencialidades de 192 accesiones de Capsicum L., procedentes de 21 países, se realizó la caracterización morfológica y agronómica mediante la aplicación de 57 descriptores cualitativas y cuantitativas. Los análisis multivariados identificaron dos grandes grupos: C. annuum (G3, G5, G7 y G8) y C. frutescens, C. baccatum, C. chinense y C. pubescens (G1, G2, G4, G6 y G9). Los descriptores cualitativos discriminantes fueron color de la corola, color de las anteras y posición de la flor. Las características cuantitativas discriminante fueron longitud, peso y ancho del fruto. La selección participativa identificó 15 materiales por color, olor, textura, sabor, tamaño y grosor de frutos. Los análisis químicos determinaron la mayor concentración de flavonoides en las accesiones 10,757 (16.64 mg/g) y 15,661 (15.77 mg/g). Los contenidos de polifenoles más alto presentaron las accesiones 17,750 (11.68 mg/g) y 10,757 (11.41 mg/g). La mayor concentración de capsaicina se presentó en la accesión 16,209 (55.90 mg/g) y 10,757 (48.80 mg/g). El valor más alto de antioxidante se registró en las accesiones 17,750 (90.85 mg/g) y 15,661 (87.03 mg/g). Todas estas son características importantes con vistas a incrementar el uso industrial y procesos de mejora genética. Los resultados muestran la existencia de una variabilidad genética significativa en Capsicum.
Palabras claves: germoplasma; recursos genéticos; accesiones; descriptores.

Appendix B

Table A1. Results of the participatory sensory evaluation for 34 selected accessions of Capsicum spp. CATIE. Costa Rica.
Table A1. Results of the participatory sensory evaluation for 34 selected accessions of Capsicum spp. CATIE. Costa Rica.
AccessionTaste *Odour *Texture *Pulp Thickness *Colour *Size *Total
15,66155555530
781844444424
913933455-- **20
16,46034355--20
17,15143544--20
10,88644444--20
12,91134445--20
14,75733455--20
9916b33333318
16,46234344--18
16,45444343--18
16,45844424--18
8994 33333318
10,75733333318
16,20933333318
22,11933333318
17,26833333318
989233333318
17,75033333318
16,30433333318
9902 33333318
11,20443343--17
16,45043343--17
16,45743333--16
7816--3--34--10
9186------53--8
11,745--1--23--6
16,521----3--3--6
18,757------23--5
20,0161----22--5
16,275--11--114
18,7781--111--4
9183----1--2--3
7819------1----1
Total 510
* Excellent 5; Very Good 4; Good 3; Regular 2; Poor 1; ** Variables that were not of interest.

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Figure 1. Dendrogram obtained by hierarchical cluster analysis (Ward’s method, Gower’s distance) with qualitative and quantitative variables from the morphological characterization of 192 accessions of chilli (Capsicum spp.).
Figure 1. Dendrogram obtained by hierarchical cluster analysis (Ward’s method, Gower’s distance) with qualitative and quantitative variables from the morphological characterization of 192 accessions of chilli (Capsicum spp.).
Agronomy 10 01732 g001
Figure 2. Biplot graph obtained from the principal component analysis of the 15 Capsicum accessions.
Figure 2. Biplot graph obtained from the principal component analysis of the 15 Capsicum accessions.
Agronomy 10 01732 g002
Table 1. Origin and number of accessions of each of the species of Capsicum spp.
Table 1. Origin and number of accessions of each of the species of Capsicum spp.
Capsicum Species
OriginC. annuumC. frutescensC. chinenseC. baccatumC. pubescensNot Identified
Peru1----5----
Panama352----2
Costa Rica83021--4
Mexico214--1----
Honduras--72----1
Guatemala306----16
El Salvador48--------
Ethiopia52------1
Zimbabwe1----------
Spain2------
Malaysia10--------2
U.S.A.1----------
Syria1----------
Russia2----------
Ecuador------2----
Brazil1----2--1
Philippines----------1
Cuba----------1
Colombia--1--------
Nicaragua--1--------
Maldives1----------
Table 2. Capsicum morphological qualitative descriptors.
Table 2. Capsicum morphological qualitative descriptors.
DescriptorState DescriptorState
Hypocotyl colourWhite, Green, PurpleCorolla spot colourWhite, Yellow, Yellowish Green, Green, Purple, Other
Hypocotyl pubescenceSparse, Medium, DenseAnther colourWhite, Yellow, Pale Blue, Blue, Purple, Other
Cotyledon leaf colourLight Green, Green, Dark Green, Light Purple, Purple, Dark Purple, Variegated, Yellow, OtherAnthocyanin spots or stripesAbsent, present
Cotyledon leaf shapeDeltoid, Oval, Lanceolate, Elongated-deltoidIntermediate state fruit colourWhite, Yellow, Green, Orange, Purple, Dark Purple, Other
Stem colourGreen, Green with purple stripes, Purple, OtherMature state fruit colourWhite, Lemon-Yellow, Pale Yellow-Orange, Yellow-Orange, Pale Orange, Orange, Light Red, Red, Dark Red, Purple, Brown, Black, Other
Node anthocyaninGreen, Light purple, Purple, Dark purpleFruit shapeElongated, Almost round, Triangular, Campanulate, Blocky, Other
Stem shapeCylindrical, Angled, FlattenedFruit shape at junction with pedicelAcute, obtuse, truncated, chordate, lobate
Stem pubescenceSparse, Medium, DenseNeck at fruit baseAbscent, present
Plant growth habitProstrate, Intermediate, ErectShape fruit apexPointed, Blunt, Sunken, Sunken and pointed, Other
Branching densitySparse, Medium, DenseAppendix in the fruitAbscent, present
TilleringSparse, Medium, DenseFruit cross-sectional corrugationSlightly corrugated, Inter-mediate, Very corrugated
Leaf densitySparse, Medium, DenseFruit epidermis type (surface)Smooth, Semi-wrinkled, wrinkled
Leaf colourYellow, Light Green, Green, Dark Green, Light Purple, Purple, Heather, OtherPersistence of pedicel with fruitSlight, Intermediate, Persistent
Leaf shapeDeltoid, Oval, LanceolatePersistence of pedicel with stemSlight, Intermediate, Persistent
Leaf blade marginWhole, Wavy, CiliatedSeed colourLight Yellow, Dark Yellow, Black
Leaf pubescenceEscasa, Intermedia, DensaSeed surfaceSmooth, Rough, Wrinkled
Flower positionPendant, Intermediate, ErectSusceptibility to biological stressVery low or no visible signs of incidence, Low, Inter-mediate, High, Very high
Corolla colourWhite, Light yellow, Yellow, Greenish yellow, Purple with white base, White with purple base, White with purple margin, Purple, OtherChilli flavourSweet, spicy
Table 3. Capsicum morphological quantitative descriptors.
Table 3. Capsicum morphological quantitative descriptors.
DescriptorUnit of MeasureDescriptorUnit of Measure
Plant heightcmFruit lengthcm
Plant widthcmFruit widthcm
Plant height/width ratiocmFruit weightg
Stem lengthcmFruit pedicel lengthcm
Stem widthcmFruit wall thicknessmm
Length mature leafcmDays to fruitingnumber
Width mature leafcmWeight of 1000 seedsg
Leaf l/w rationumberPlacenta lengthcm
Days to floweringnumberSeed sizemm
No. flowers leaf axil−1numberClassification seed no. fruit−1number
Fruit setnumber
Table 4. Description of the 9 groups of accessions from Figure 1, including species identification.
Table 4. Description of the 9 groups of accessions from Figure 1, including species identification.
Group 15440 b, 7203 b, 7209 b, 7417 b, 16,463 b, 16,209 b, 17,268 s, 18,060 a, 18,645 b
Group 27300 c, 8386 f, 9892 f, 10,757 c, 10,792 f, 10,793 f, 14,757 a, 16,308 p, 22,115 s, 22,119 s
Group 35445 b, 6123 a, 7816 a, 8058 s, 9135 a, 9139 a, 9186 a, 10,886 s, 11,757 f, 12,911 f, 14,376 a, 15,239 a, 15,407 a, 15,412 a, 15,422 a, 15,449 a, 15,587 a, 15,632 a, 15,646 a, 15,653 a, 15,661 a, 15,983 a, 16,270 a, 16,297 a, 16,304 a, 16,458 a, 16,462 a, 16,467 a, 17,151 a, 17,294 a, 18,314 a, 18,631 a, 18,651 a, 18,660 a, 18,757 a, 19,259 a
Group 48248 f, 8394 a, 8998 s, 8999 f, 9015 f, 9140 a, 9159 f, 9201 a, 9777 f, 9781 f, 9801 f, 9811 f, 9832 f, 9837 f, 9902 f, 9923 f, 10,003 c, 10,730 f, 10,762 f, 10,862 f, 10,909 f, 10,951 f, 11,073 f, 11,198 f, 11,744 f, 11,745 f, 12,017 f, 12,097 f, 12,154 c, 12,156 c, 12,910 b, 13,328 s
Group 59038 a, 9096 f, 9115 a, 9183 a, 9226 a, 11,303 a, 15,395 f, 16,450 a, 16,452 a, 16,453 s, 16,454 a, 16,456 a, 16,457 a, 16,460 a
Group 66126 f, 7216 s, 8534 s, 8567 a, 9095 f, 9200 f, 9204 f, 10,760 f, 10,871 f, 10,903 f, 10,946 f, 11,050 f, 11,717 s, 15,237 a, 15,654 f, 15,932 a, 16,273 a, 16,308 a, 16,513 f, 18,229 f
Group 76143 a, 7818 a, 7819 a, 8047 a, 8055 s, 8064 a, 9053 f, 9110 b, 9131 a, 10,630 a, 10,691 a, 11,204 s, 11,232 a, 11,305 a, 11,795 a, 13,963 a, 14,751 a, 14,756 a, 15,389 s, 15,434 f, 15,440 a, 15,640 a, 15,641 a, 15,651 a, 15,658 a, 15,976 s, 16,276 a, 16,451 s, 16,521 a, 20,029 a
Group 89269 a, 16,459 a, 16,461 a, 17,867 a, 18,156 a, 18,776 a, 18,787 a, 18,788 a, 18,804 a, 18,815 a
Group 96586 f, 7218 c, 7257 a, 8395 c, 8994 s, 9016 f, 9037 f, 9040 a, 9043 f, 9079 f, 9097 f, 9103 f, 9803 f, 9835 f, 9839 f, 9841 f, 9916 f, 9917 f, 9921 f, 10,005 f, 10,015 f, 11,755 f, 14,776 f, 15,914 f, 16,275 a, 16,280 s, 17,247 a, 17,750 c, 18,778 a, 20,016 s
aC. annuum; bC. baccatum; cC. chinense; fC. frutescens; pC. pubescens; sCapsicum spp.
Table 5. Qualitative descriptors with the highest discriminant value influencing the genetic groups’ separation of Capsicum species.
Table 5. Qualitative descriptors with the highest discriminant value influencing the genetic groups’ separation of Capsicum species.
CharacterX2Coeficient (P)Cramer (V)
Colour of the corolla 325.34 **0.790.58
Colour of the anthers 323.70 **0.790.65
Position of the flower 166.04 **0.680.54
Leaf distance 144.82 **0.660.50
Branching distance 141.30 **0.650.50
Susceptibility to biological stress 129.04 **0.630.37
Corollar spot colour 126.36 **0.630.47
Tillering 123.08 **0.630.46
Anthocyanin of the node 106.07 **0.600.37
Cross wrinkling of the fruit 102.59 **0.590.42
Fruit shape at the junction with the pedicel 97.38 **0.580.32
Stem pubescence 95.95 **0.580.41
Leaf pubescence 86.83 **0.560.39
Persistence of the pedicel with the stem 82.99 **0.550.38
Fruit colour in the intermediate state 75.09 **0.530.28
Type of epidermis of the fruit 73.85 **0.530.36
Persistence of the pedicel with the fruit 70.41 **0.520.35
Fruit shape 69.66 **0.520.27
Shape of cotyledonal leaf 66.37 **0.510.34
Colour of the hypocotyl 64.24 **0.500.33
Shape of fruit tip 63.75 **0.500.29
Leaf margin 63.14 **0.500.41
Growth habit 62.76 **0.500.33
Pubescence of hypocotyl 62.48 **0.500.33
Leaf colour 59.32 **0.490.32
Ovary length 51.49 **0.460.30
Seed size 38.59 **0.410.32
Neck at the base of the fruit 33.99 **0.390.30
Cotyledonal leaf colour 31.91 **0.380.24
Anthocyanin stains or streaks of the fruits 27.14 **0.350.27
** = high significance with (p < 0.0001).
Table 6. Eigenvalues determined by the canonical discriminant function discriminating grouping of Capsicum spp. accessions.
Table 6. Eigenvalues determined by the canonical discriminant function discriminating grouping of Capsicum spp. accessions.
VariablesAxis 1Axis 2
Leaf length/width ratio2.35−0.81
Width mature leaf0.810.09
Fruit length0.36−0.08
Fruit width0.230.82
Fruit wall thickness0.09−0.21
Plant height0.03−0.04
Days to flowering0.01−0.01
Fruit weight1.80 × 10−3−2.20 × 10−3
Plant width−0.020.06
Stem length−0.020.02
Days to fruiting−0.02−0.02
No. flowers leaf axil-1−0.51−0.38
Fruit pedicel length−0.550.45
Weight of 1000 seeds−0.600.19
Length mature leaf−0.73−0.10
Plant height/width radio−1.070.47
Stem width−1.220.60
Table 7. Flavonoid, polyphenol and capsaicin concentrations in seven accessions representing four species of Capsicum in the CATIE genebank.
Table 7. Flavonoid, polyphenol and capsaicin concentrations in seven accessions representing four species of Capsicum in the CATIE genebank.
SpeciesAccession No.Flavonoid Concentration (mg/g)Polyphenol Concentration (mg/g)Capsaicin Concentration (mg/g)
C. chinense10,75716.64 fh11.414.88
15,66115.7710.690.32
C. annuum781811.417.152.64
14,75711.906.911.37
16,30410.745.970.99
16,4508.94 fl4.52 pl0.20 cl
16,45411.687.831.34
16,45712.417.981.65
16,46211.486.791.10
17,75013.5911.68 ph4.60
C. frutescens781612.057.464.61
989213.308.563.14
990211.095.122.80
C. baccatum16,20910.306.735.59 ch
Capsicum spp.11,20410.045.452.02
fh—highest flavonoid concentration; fl—lowest flavonoid concentration; ph—highest polyphenol concentration; pl—lowest polyphenol concentration; ch—highest capsaicin concentration; cl—lowest capsaicin concentration.
Table 8. Average, standard deviation, coefficient of variation, minimum and maximum values for the characteristics of the nutritional value of 15 accessions of chilli (Capsicum spp.).
Table 8. Average, standard deviation, coefficient of variation, minimum and maximum values for the characteristics of the nutritional value of 15 accessions of chilli (Capsicum spp.).
VariableAverageStandard Deviation Coefficient of VariationMínimum ValuesMaximum Values
Humidity %6.482.8744.322.7713.75
Polyphenols mg/g7.622.1828.694.5211.68
Flavonoids mg/g12.092.0617.028.9416.64
Capsaicinoids mg/g2.481.7470.120.205.59
Antioxidants mg/g68.6613.6919.9347.8490.85
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Paredes Andrade, N.J.; Monteros-Altamirano, A.; Tapia Bastidas, C.G.; Sørensen, M. Morphological, Sensorial and Chemical Characterization of Chilli Peppers (Capsicum spp.) from the CATIE Genebank. Agronomy 2020, 10, 1732. https://doi.org/10.3390/agronomy10111732

AMA Style

Paredes Andrade NJ, Monteros-Altamirano A, Tapia Bastidas CG, Sørensen M. Morphological, Sensorial and Chemical Characterization of Chilli Peppers (Capsicum spp.) from the CATIE Genebank. Agronomy. 2020; 10(11):1732. https://doi.org/10.3390/agronomy10111732

Chicago/Turabian Style

Paredes Andrade, Nelly Judith, Alvaro Monteros-Altamirano, Cesar Guillermo Tapia Bastidas, and Marten Sørensen. 2020. "Morphological, Sensorial and Chemical Characterization of Chilli Peppers (Capsicum spp.) from the CATIE Genebank" Agronomy 10, no. 11: 1732. https://doi.org/10.3390/agronomy10111732

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