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Article

Characterization of 75 Cultivars of Four Capsicum Species in Terms of Fruit Morphology, Capsaicinoids, Fatty Acids, and Pigments

by
Pingping Li
1,2,†,
Xiang Zhang
1,†,
Yuting Liu
1,†,
Zhihe Xie
1,
Ruihao Zhang
1,
Kai Zhao
1,*,
Junheng Lv
1,*,
Jinfen Wen
3,* and
Minghua Deng
1,*
1
College of Horticulture and Landscape, Yunnan Agricultural University, Kunming 650201, China
2
Sericulture and Apiculture Research Institute, Yunnan Academy of Agricultural Sciences, Mengzi 661101, China
3
Faculty of Architecture and City Planning, Kunming University of Science and Technology, Kunming 650500, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Appl. Sci. 2022, 12(12), 6292; https://doi.org/10.3390/app12126292
Submission received: 23 May 2022 / Revised: 15 June 2022 / Accepted: 17 June 2022 / Published: 20 June 2022
(This article belongs to the Special Issue Advances in Food and Food By-Products Analysis: Physical Characterization and Nutrient Analysis)
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Versions Notes

Abstract

:
Fruit quality has long been well known as an important prerequisite for evaluating pepper resources. In the study, 75 cultivars belonging to four Capsicum species were investigated on the bases of fruit morphology and concentrations of fruit secondary metabolites. The results showed that C. annuum had a greater variation than C. chinense and C. frutescens in terms of fruit weight, size and contents of carotenoids, anthocyanidins, and capsaicinoids. Moreover, there were significant differences in the concentrations of total phenol, total soluble sugar, total soluble solids, titratable acid, and total soluble protein of all samples. Capsaicin and dihydrocapsaicin were the most important capsaicinoids components in pepper fruits, of which C. chinense both had the highest levels, whereas some accessions of C. annuum were not detected. Eighteen fatty acids were detected in pepper fruits, and the dominant member was linoleic acid (a polyunsaturated fatty acid) therein. We integrated a set of methods for metabolites, and the results indicated that there was a positive correlation between concentrations of capsaicinoids and fatty acids. Four accessions had the highest contents of quality-related compounds, two of which belonged to C. chinense (S23 and S24) and possessed high levels of capsaicin. However, S67 had a high level of β-carotene and S68 contained higher contents of total fatty acid and ascorbic acid, and both of them belonged to C. annuum. This work could provide a valid experimental basis for the potential application value of the four accessions mentioned above.

1. Introduction

Peppers (Capsicum spp.) are economically important agricultural and horticultural crops. They are of great economical value because of their outstanding contributions as important sources of spices and high antioxidants [1,2]. The Capsicum genus comprises more than 30 described species, and the fruits of that exhibit variability widely with respect to shape, size, color, and sensory attributes [3]. Among these species, five are considered to be domesticated: Capsicum annuum (sweet or bell pepper), Capsicum frutescens (chili pepper), Capsicum chinense (Scotch pepper chili), Capsicum baccatum (aji amarillo chili), and Capsicum pubescens (apple chili) [4]. The general nutrient compounds of pepper, with its array of vitamins, phenolic, carotenoids, and capsaicinoids, have beneficial effects for humans, including antioxidant and antibacterial properties [2,5].
The main quality features of pepper fruits are color and spice level [6]. The pungency of the ripe fruits in peppers is due to the presence of capsaicinoids, which is a group of many different alkaloids. Capsaicin and dihydrocapsaicin are the major alkaloids which account for 90% of the total capsaicinoids in chili peppers [7,8]. Twenty-three capsaicinoids have been reported up to now, and the pungency level of fruit is related with their molecular structure and concentrations [9,10]. The fruit of pepper contains 46–243 mg/100 g ascorbic acid (vitamin C) by fresh weight, which depend on different species and cultivars as well as degree of ripeness [4,11]. Ascorbic acid is an antioxidant that plays a vital role in human nutrition and body function, being actively involved in neutralizing free radicals, iron assimilation, the wound healing process, and protecting the skin from viral and bacterial infection by building collagen in the skin [12].
The ripe fruits of pepper varieties display a wide range of colors, which have been traditionally generated by the accumulation of different carotenoids and flavonoids in the pericarp [13]. Carotenoids are naturally occurring pigments found in plants and responsible for different colors of peel, with covering red, brown, orange, salmon-pink, and yellow [13,14]. In recent years, carotenoids have attracted widespread attention because of their higher antioxidant activity and positive health benefits for preventing cardiovascular diseases [15,16]. Particularly, carotenoids containing k-terminal have been proved to be one of the characteristics of peppers [17]. Anthocyanins, as the final products of the flavonoid biosynthesis pathway, mainly accumulate in the outer epidermis of pepper fruit [18]. However, the major components are delphinidin, cyanidin and malvidin derivatives therein, and that is why some pepper fruits appear with purple or black colors, which are related to the concentrations and proportions of various anthocyanins in fruits at different development stages or genotypes [13,18].
The nutritional value of the fatty acids profile depends on their ratio and constitutes. A reasonable fatty acid composition should include low saturated fatty acid, high monounsaturated fatty acid, balanced omega-6 and omega-3 fatty acids, and a large number of vitamin E and phytosterols. The lipids of pepper fruits are vital quality features as they play an important role in preparation for attractive spice. Fatty acids accumulate both in the peel and seeds of pepper fruits [19].
It is obvious that the discrepancy of capsaicinoids and metabolites in different varie-ties may be helpful for further pepper breeding programs. Thus, the present study was designed to evaluate the diversity of traits involving fruit morphology, the concentrations of capsaicinoids and other metabolites in 75 different Capsicum genotypes mainly collected from Yunnan Province, China. Integrating the biochemical and molecular mechanisms underlying this variation could be instructive for developing new commercial hybrid cultivars with fruits rich in health-related compounds.

2. Materials and Methods

2.1. Chemicals

Tridecanoic acid, ascorbic acid, and capsaicinoids (capsaicin, dihydrocapsaicin, and nordihydrocapsaicin) were purchased from the National Institutes for Food and Drug Control (Beijing, China). Standards of anthocyanidins (delphinidin chloride, petunidin chloride, cyanidin chloride, pelargonidin chloride, peonidin chloride, malvidin chloride) and carotenoids (capsanthin, β-carotene, and zeaxanthin) were obtained from Extrasynthese (Genay, France). Fatty acid methyl ester mix (C4–C24) was purchased from Nu-check Prep, Inc. (Elysian, MN, USA). Methanol, ethanol, phosphoric acid, and other organic solvents of HPLC grade were obtained from MREDA (Beijing, China). All other chemicals used in this study were reagent grade, unless otherwise stated.

2.2. Plant Material

Seventy-five pepper cultivars were cultivated in Kunming (24°59′15″ N, 103°10′43″ E) and Wenshan (23°35′15″ N, 104°21′32″ E) (Yunnan Province, China), and fresh samples of fruit were harvested from each cultivar. These 75 genotypes included 67 genotypes of C. annuum, three genotypes of C. frutescens, four genotypes of C. chinense, and one genotype of C. baccatum (Table 1). The fruits, free from insect pests, diseases, or bruising, were harvested at random at the commodity maturity stage and at a similar size for each cultivar. The peppers were picked at random from different parts of the plant and from different areas of the field, in order to obtain a representative sample. The fruits were stored at −20 °C until processing.

2.3. Morphological Parameters and Metabolite Composition

The average weight of each sample (10 fruits per replicate sample, three replicates) was determined using a digital balance (OHAUS, Parsippany, NJ, USA). Average fruit length and diameter were measured using vernier calipers (Mitutoyo, Kanagawa, Japan). Total soluble solids of pepper fruits of each cultivar were determined using a digital refractometer (ATAGO, Tokyo, Japan) and expressed in °Brix. Titratable acidity was determined by using the 0.1 N NaOH titration method and expressed in % citric acid-equivalents [20]. Total phenolic concentration was determined using the Folin–Ciocalteu method [21], expressed relative to a standard curve of gallic acid, and presented as grams of gallic acid equivalents/kg tissue fresh weight. The soluble sugar concentration of the fruits of each cultivar was determined by the anthrone colorimetric method [22]. Total soluble protein content was measured according to the method of Bradford [23] using bovine serum albumin as the protein standard. Ascorbic acid was determined by HPLC as described by Jiménez et al. [24], and the HPLC chromatogram of identified compounds and standards is shown in Supplemental Figure S2.

2.4. Carotenoid Extraction, Identification, and Determination

The carotenoid pigments were extracted from samples (0.5 g of fruit per replicate sample, three replicates) of the 75 cultivars according to standard procedures [25,26] with some modifications. An aliquot (0.5 g) of the fresh tissue sample was snap-frozen in liquid nitrogen and ground into a powder with a mortar and pestle. The powder was quickly transferred to a 15 mL centrifuge tube, to which was added a 10 mL mixture solution of absolute ethanol and dichloromethane (1:1, v/v). After homogenization, the sample suspension was incubated for 30 min at 50 °C and then centrifuged at 10,000× g for 15 min at 4 °C, whereafter the supernatant was collected and adjusted to 10 mL with the mixture solution mentioned above. Subsequently, the final supernatant was filtered through a 0.45 µm nylon filter to obtain the filtrate for analysis. The whole extraction and analytical process was operated in the dark under a safelight.
Carotenoids were identified and their relative masses quantified (Infinity II 1260, Agilent, Santa Clara, CA, US) with an ultraviolet detector and an Agilent Zorbax SB-C18 column (250 × 4.6 mm, 5-µm particle size) [10]. The mobile phases used were methanol/acetonitrile (55:45, v/v; solvent A) and methyl tert-butyl ether (solvent B, running at a flow rate of 1.0 mL/min and a temperature of 30 °C). Injected volumes were 20 µL for calibration and 20 µL for the samples. The eluent A: eluent B were isocratic flow 90:10 (v/v). Carotenoids eluted from the column were detected at 450 nm. Quantities of each carotenoid were determined by comparison the standards using the regression equations and were then expressed as μg/g. The HPLC chromatogram of identified compounds and standards is shown in Supplemental Figure S3.

2.5. Capsaicinoid Extraction, Identification, and Determination

The capsaicinoids were extracted according to the published method [27] with some modifications. An aliquot (0.5 g) of pepper fruit powder was added in 10 mL methanol: tetrahydrofuran mixture 1:1 (v/v) and extracted by ultrasound sonication for 40 min. After that, the extract liquid was centrifuged at 4000× g for 5 min at 4 °C, and the supernatant was retained. The extraction procedure was repeated twice, and the supernatants were pooled, concentrated by a rotary evaporator at 70 °C. The final volume was adjusted to 10 mL with a methanol–tetrahydrofuran mixture (1:1, v/v), then the sample was filtered through a 0.45 μm nylon filter (Millipore, Bedford, MA, USA) for subsequent analysis.
Capsaicinoids were separated and detected at 280 nm by HPLC (as mentioned above) according to the procedure described by Ma et al. [28]. A Zorbax SB-C18 column (250 × 4.6 mm i.d.) with 5 µm particle size was operated at 30 °C. The solvent was a methanol: water system (65:35 by volume) at a flow rate of 1 mL/min, and temperature was maintained at 30 °C. The injection volume was 10 µL. Quantities of each capsaicinoid were determined by comparison of the standards (capsaicin, nordihydrocapsaicin and dihydrocapsaicin) using the regression equations and were then expressed as μg/g. The HPLC chromatogram of identified compounds and standards is shown in Supplemental Figure S4.

2.6. Anthocyanin Extraction, Hydrolysis, Identification, and Quantification

The extraction and hydrolysis of anthocyanin were performed according to the method described by Lightbourn et al. [18] with some modifications. An aliquot (0.5 g sample) of fresh fruit tissue was snap-frozen using liquid nitrogen and ground into powder in a mortar and pestle. Afterwards, an extraction solvent made of 15 mL 95% ethanol and 1.5 mol/L HCl was added to the powder. Then the mixture was transferred to a 15 mL centrifuge tube and treated ultrasonically at 100 W for 30 min. The tube was centrifuged at 5000× g for 5 min, and the residue was subjected to extraction for a second time. The two supernatants were pooled, and the volume was adjusted to 50 mL. A total of 3 mL supernatant was added into 1 mL 3 N HCl, and the reaction solution was incubated for 40 min at 90 °C and then placed in an ice box to cool. This hydrolyzed solution was filtered to obtain pure anthocyanidins through a 0.45 μm nylon filter membrane.
Anthocyanidin separation, identification, and quantification were performed following the procedures described by Lightbourn et al. [18], using HPLC (as mentioned above) equipped with a variable wavelength detector and a Zorbax SB-C18 column (i.d. 4.6 mm × 250 mm, 5 μm particle size). The mobile phase consisted of two solvents: 10% (v/v) aqueous formic acid (solvent A) and 10% (v/v) formic acid in methanol (solvent B) with a flow rate of 0.8 mL/min. The following linear gradient program was used: 90% solvent A for 5 min, 70% solvent A for 15 min, then 40% solvent A for 20 min, and returning to 90% solvent A for 30 min, with a column temperature maintained at 30 °C and an injection volume of 5 μL. Six anthocyanidin standards (delphinidin, petunidin, cyanidin, pelargonidin, peonidin, malvidin) were prepared before injection. Anthocyanidins were detected at 520 nm. The HPLC chromatogram of identified compounds and standards is shown in Supplemental Figure S5.

2.7. Lipid and Fatty Acid Determination

Total lipid concentration was quantified by the methods of the Association of Official Analytical Chemists, which uses a chloroform: methanol (2:1) system as extractant solvent (AOAC, 2006). The fatty acid of the sample was detected according to O’Fallon et al. [29]. The derivatives were then injected into an Agilent7890B gas chromatograph system (Santa Clara, CA, USA) equipped with a flame ionization detector and an HP-5 column (30 m × 0.32 mm i.d.). Nitrogen was used as the carrier gas (1.25 mL/min), the injector was set at 250 °C, and the detector was set at 300 °C. The split ratio was 10:1. The initial oven temperature was 100 °C, which was maintained for 13 min; it was subsequently increased to 180 °C at a rate of 10 °C/min and held for 6 min, then increased to 200 °C at a rate of 1 °C/min and held for 20 min, and finally increased to 230 °C at a rate of 4 °C/min and held for 10 min. All fatty acids were identified and quantified using authentic standards (Nu-Chek, Elysian, MN, USA). The HPLC chromatogram of identified compounds and standards is shown in Supplemental Figure S6.

2.8. Statistical Analysis

The singular value decomposition method was used to perform principal component analysis (PCA) and cluster analysis was perfomed by the online software ClustVis [30] to present the diagram. Using the rcorr function in the Hmisc package of the R program, Pearson’s correlation coefficient plot was drawn according to Pearson’s correlation coefficient method (p = 0.05) in the Corrplot function. The gbmplus package of R program was taken to generate aggregated boosted tree, which can be used for researching the relationship between the contents of capsaicin, dihydrocapsaicin and nordihydrocapsaicin and that of the fatty acids.

3. Results

3.1. Morphological Parameters and Chemical Parameters

The fruit morphology of 75 peppers is shown in supplemental Table S1 and Figure S1. Genotypes of 75 accessions of pepper were classified into C. annuum (67), C. baccatum (1), C. chinense (4), and C. frutescens (3). It was found that C. annuum has the greatest variation in fruit morphology, followed by C. chinense, especially fruit shape and length, while C. frutescens were mostly one type of fruit shape among the collected accessions (Supplemental Table S1). The fruit shapes across the four species were short horn (54), long finger (5), lantern (5), short finger (4), long cone (3), elongate (3) and long horn (1) (Supplemental Table S1). The range of fruit color varied from dark green (46) to olivine (12), orange (6), red (5), purple-black (5), and brown (1).
Furthermore, the fruit weight, length, and diameter were also found to be significant variables, depending on the species. Individual fruit weight ranged from 0.64 g (S71, C. annuum) to 34.13 g (S46, C. annuum), with a mean of 2.99 g (Supplemental Tables S1 and S2). The fruit length ranged from 1.58 cm (S50, C. annuum) to 15.37 cm (S59, C. annuum), with a mean of 5.07 cm. The fruit diameter ranged from 0.52 cm (S43, C. annuum) to 4.35 cm (S46, C. annuum), with a mean of 1.09 cm. The coefficients of variation of fruit weight, length, and diameter were 153.21%, 39.90%, and 76.73%, respectively (Supplemental Table S2). Fruit weight, length, and diameter of the C. frutescens accessions were 1.13–3.08 g, 3.32–5.12 cm, and 0.78–4.32 cm, respectively, those of C. chinense were 6.12–7.67 g, 2.67–6.48 cm, and 2.19–3.40 cm, respectively, and those of C. annuum were 0.64–34.13 g, 1.58–15.37 cm, and 0.52–3.95 cm, respectively (Supplemental Table S1). The results of significant analysis showed that there was no significant difference in fruit length among three pepper species (p > 0.05). However, the fruit weight of C. chinese was significantly higher than that of C. frutescens (p < 0.05), and the C. annuum was not significantly different from that of C. chinese and C. frutescens (p > 0.05). Meanwhile, the diameter of C. annuum was significantly lower than that of C. chinese and C. frutescens (p < 0.05), and there was no significant difference between C. frutescens and C. chinese (p > 0.05) (Supplemental Table S3).
Chemical compositions of the 75 genotypes peppers were summarized in Table 1. Among them, the total phenol concentration of S24 (C. chinense) was the highest (12.13 mg/g), while that of S61 (C. frutescens) was the lowest (1.89 mg/g). The soluble sugar concentration of all 75 accessions ranged from 5.45 mg/g (S25, C. annuum) to 62.40 mg/g (S59, C. annuum). The total soluble solid concentration ranged from 0.25 °Brix (S42, C. frutescens) to 1.34 °Brix (S68, C. annuum). The titratable acid ranged from 0.14% (S59, C. annuum) to 0.63% (S60, C. annuum), while the total soluble protein concentration ranged from 0.41 mg/g (S22, C. annuum) to 10.62 mg/g (S25, C. annuum). The coefficients of variation of total phenol, total soluble sugar, total soluble solids, titratable acid, and total soluble protein were 12.13%, 62.40%, 1.34%, 0.63%, and 76.73%, respectively (Supplemental Table S2). There was no significantly difference in titratable acidity among the three pepper species (p > 0.05). The total soluble sugar and total soluble solids of C. frutescens were significantly lower than the values of C. chinese and C. annuum (p < 0.05), and there was no significant difference between C. annuums and C. chinese (p > 0.05). Moreover, the phenol content of C. chinese was significantly lower than that of C. frutescens and C. annuum (p < 0.05), and there was no significant difference between C. annuums and C. frutescens (p > 0.05). Finally, the total soluble protein of C. chinese was significantly lower than that of C. annuum (p < 0.05), and the C. frutescens was not significantly different from that of C.chinese and C. annuum (p > 0.05) (Supplemental Table S3).

3.2. Carotenoid, Anthocyanidin, Capsaicinoids, and Ascorbic Acid Concentrations

The carotenoid profiles (capsanthin, zeaxanthin, and β-carotene) in pepper fruit were separated and detected to gain insightful information about them by HPLC (Table 1). Among them, S59 (C. annuum, brown) had the highest capsanthin content (170.92 μg/g), whereas this red carotenoid was not detected in 17 pepper accessions, including S02 (C. annuum, purple black), S03 (C. annuum, olivine), S04 (C. annuum, olivine), and S05 (C. annuum, dark green). Zeaxanthin was present in all the accessions investigated. S43 (C. annuum, dark green) had the highest concentration of zeaxanthin (118.91 μg/g), whereas S04 (C. annuum, olivine) had the lowest concentration (2.69 μg/g) of it. S67 (C. annuum, red) had the highest concentration of β-carotene (11,158.94 μg/g), but it was not detected in seven pepper accessions, including S03 (C. annuum, olivine), S09 (C. annuum, orange), and S19 (C. annuum, olivine) (Table 1). The coefficients of variation of capsanthin, zeaxanthin, and β-carotene were 182.36%, 64.75%, and 118.17%, respectively (Supplemental Table S2). There was no significantly difference in capsanthin and β-carotene among the three pepper species (p > 0.05). However, the zeaxanthin of C. annuum was significantly higher than that of C. chinese and C. frutescens (p < 0.05), and the C. frutescens was not significantly different from that of C. chinese (p > 0.05) (Supplemental Table S3).
The 75 pepper samples were screened for the six anthocyanidins, but only the blue delphinidin was detected in the fruits (Table 1). The test results showed that S69 (C. annuum, purple-black) had the highest concentration of delphinidin (2370.10 μg/g); nevertheless, it was not detected in 30 pepper accessions, including S01 (C. annuum, orange), S03 (C. annuum, orange), and S04 (C. annuum, olivine) (Table 1). The coefficient of variation of delphinidin was 145.66% (Supplemental Table S2). The delphinidin of C. annuum was significantly higher than that of C. frutescens and C. chinese (p < 0.05), and it was not detected in C. chinese and C. frutescens (Supplemental Table S3).
Assaying of the capsaicinoids concentration found that there were significant differences in the concentration of capsaicinoids among the 75 accessions (Table 1). The coefficients of variation of nordihydrocapsaicin, capsaicin, and dihydrocapsaicin were 182.36%, 64.75%, and 118.17%, respectively (Supplemental Table S2). It should be noted that the amount of the three capsaicinoids were all the highest in S24 (C. chinense), which corresponded to 1.83 mg/g, 22.96 mg/g, and 13.86 mg/g, respectively. None of the capsaicinoids were detected in accessions S09 (C. annuum) and S68 (C. annuum). Additionally, dihydrocapsaicin and nordihydrocapsaicin were absent from S25 (C. annuum) (Table 1). Nordihydrocapsaicin, capsaicin, and dihydrocapsaicin of C. chinese were significantly higher than that of C. annuum amd C. frutescens (p < 0.05), and the C. frutescens was not significantly different from that of C. annuum (p > 0.05) (Supplemental Table S3).
Analysis of ascorbic acid indicated that there were significant differences in the 75 pepper samples (Table 1). Among them, S59 (C. annuum) had the highest ascorbic acid concentration (1517.32 μg/g), whereas S20 (C. frutescens) has the lowest value (3.48 μg/g). The coefficient of variation of ascorbic acid was 87.00% (Supplemental Table S2). There was no significantly difference in ascorbic acid among the three pepper species (p > 0.05).

3.3. Fatty Acid Concentration and Composition

The concentrations and composition of fatty acids in the samples are shown in Table 2. The range of total fatty acid was from 1.80% to 10.94%. A total of 18 fatty acids were detected in the 75 pepper fruits tested (Table 2). Of these, seven fatty acids were found in all samples, namely caproic acid (C10:0), palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1n9c), linoleic acid (C18:2n6c), arachidic acid (C20:0), and behenic acid (C22:0) (Table 2). In the 75 pepper fruits, high levels of fatty acids were found with linoleic acid (C18:2n6c), oleic acid (C18:1n9c), and palmitic acid (C16:0), which together accounted for more than 90% of the total fatty acid content (Table 2). Furthermore, their contents ranged from 47.46% to 80.90% for linoleic acid, 7.18% to 17.50% for oleic acid, and 6.01% to 9.48% for palmitic acid, respectively (Table 2).
In the current study, linoleic acid (C18:2n6c) was the main polyunsaturated fatty acid, oleic acid (C18:1n9c) was the main monounsaturated fatty acid, and palmitic acid (C16:0) was the main saturated fatty acid (Table 2). Among these accessions, the highest proportions of fatty acids were S03 (C. annuum) for linoleic acid (80.90%), S24 (C. chinense) for oleic acid (17.50%), and S67 (C. annuum) for palmitic acid (9.48%), respectively. Additionally, saturated fatty acids accounted for 9.35% to 25.45%, monounsaturated fatty acids occupied 7.56% to 22.66%, and polyunsaturated fatty acids represented 49.85% to 82.41% in total fatty acids of the pepper fruits.

3.4. Cluster Analysis

In order to clarify the relationships among the accessions studied, a cluster analysis was performed to show the average distribution of each compound in the accessions (Figure 1). As far as the measured indicators, two main categories were concerned. The first category (Cluster I) mainly included parameters such as capsaicinoids and a variety of fatty acids, indicating that there was a positive correlation between the concentrations of capsaicinoids and fatty acids. The second category (Cluster II) contained metabolites such as capsaicin, β-carotene, zeaxanthin, and ascorbic acid. Carotenoids, such as β-carotene, zeaxanthin, etc., were clustered together due to the common carotenoid biosynthetic pathway.
The 75 pepper accessions were divided into two major groups and distinct subgroups according to the column. In the interspecific peppers, C. chinense (S22, S23, S24, S26), C. frutescens (S19, S20, S61), C. baccatum (S58), and some of the C. annuum (S02, S18, S25, S31, S32, S46, S50, S59, S67) were clustered into one large group (Cluster Ⅲ). Among them, all the C. chinense (S22, S23, S24, S26) were grouped alone into one small sub-branch. The remainder of the C. annuum accessions were grouped into a second (Cluster Ⅳ), large C. annuum-specific group. It could be seen that the relationship between C. chinense, C. frutescens, and C. baccatum was close, whereas the classification of C. annuum was differentiated.

3.5. Correlation Analysis

A correlation analysis of metabolite indicators was conducted, some of which showed significant relationships (Figure 2). The concentration of total polyunsaturated fatty acids was significantly positively correlated with that of linoleic acid (C18:2n6c) (r = 1.00, p < 0.05), which was the same as the correlation between the amount of total monounsaturated fatty acids and oleic acid (C18:1n9c) (r = 0.98, p < 0.05). In addition, there was a positive correlation between the contents of capsaicin, dihydrocapsaicin, and nordihydrocapsaicin (r > 0.66, p < 0.05). Moreover, the quantity of total saturated fatty acid was significant positively correlated with that of C16:0, C24:0, C20:0, and C18:0 (r > 0.50, p < 0.05).
Concentrations of β-carotene and capsanthin exhibited weakly positive correlations with some fatty acids (C12:0, C14:0, or C16:0) (0 < r < 0.61, p < 0.05). This rule was applied to the amount of delphinidin and total soluble protein content (r = 0.31, p < 0.05). However, the amount of zeaxanthin had a weakly negative correlation with that of some fatty acids (C20:0, C22:0, or C24:0) (−0.50 < r < 0, p < 0.05). The correlation analysis between the morphology and chemical composition of C. annuum showed that there was a weak negative correlation between the weight, length, and diameter of pepper fruit and the contents of capsaicin, dihydrocapsaicin, and nordihydrocapsaicin (r < −0.28, p < 0.05) (Supplemental Figure S7).

3.6. Principal Component Analysis (PCA)

In the study, PCA showed that there were differences among the different pepper species. The PCA score graph of the first two PCs explained 45.9% of the total variance, and the results showed the corresponding load graph (Figure 3B). It can be seen that the content characteristics of metabolite could be clearly distinguished for C. chinense (S22, S23, S24, S26), C. frutescens (S19, S20, S61), and C. annuum. The C. frutescens (S19, S20, S61) and C. annuum was highly similar in metabolite traits. Some C. chinense accessions (S23, S24) had a positive effect on PC1 and a negative effect on PC2. These accessions were characterized by a high concentration of capsaicin, dihydrocapsaicin, and β-carotene. Many content features were negative values as shown in the PC1 of Figure 3B, including ascorbic acid, total soluble solids, titratable acid, total soluble protein, C18:2n6c, total polyunsaturated fatty acids, and zeaxanthin, but the rest of the features in this study were positive values. The contents of β-carotene and capsanthin were positively correlated with those of C12:0, C14:0, and other fatty acids. Moreover, the above law of correlation was conformed to the concentrations of capsaicin, dihydrocapsaicin, and nordihydrocapsaicin with that of the C12:0, C14:0, C15:0, and C15:1 fatty acids (p < 0.05). The concentration of total monounsaturated fatty acids was significant positively correlated with that of C18:1n9c (p < 0.05), and the same as the total polyunsaturated fatty acids with that of C18:2n6c (p < 0.05) (Table 2, Figure 2).

3.7. Aggregated Boosted Tree Analysis

Analysis of the aggregated boosted tree showed that C15:1 and C16:1 made a greater contribution to nordihydrocapsaicin concentration in all of the fatty acids, accounting for 16.75% and 25.33%, respectively (Figure 4). For capsaicin, C15:0 and C16:1 were almost of importance and accounted for 15.52% and 21.89%, respectively, which was a relatively large proportion of the variation. For dihydrocapsaicin, the importance of the fatty acid components was the same as for capsaicin, but the impact was different at 15.67% (C15:0) and 19.11% (C16:1) (Figure 4). Among all of the fatty acids, C16:1 had the greatest effect on capsaicin, dihydrocapsaicin, and nordihydrocapsaicin. The content of C16:1 was significantly positively correlated with that of capsaicin, dihydrocapsaicin, and nordihydrocapsaicin. It was suggested that C16:1 may play an important role in the biosynthesis of these secondary metabolites of capsaicins.

4. Discussion

There were many reports of evaluation on pepper germplasm in recent years, which could be used to find the required excellent characters for the breeding of pepper varieties [3,31,32,33]. Morphological characteristics and chemical parameters were two extremely important factors in the study of intraspecific and interspecific genetic diversity and breeding of Capsicum [4,34]. Morphological characteristics include fruit weight, fruit color, fruit length, fruit diameter, etc., and chemical parameters mainly include total phenols, total sugar, titratable acid, ascorbic acid, capsaicinoids, carotenoids, and fatty acids.
Fruit morphology played an important role in the study of the variation and classification of pepper. There were various fruit shapes of fruits in different species of chili pepper [35,36]. The PCA analysis combining morphological characteristics and chemical parameters could divide the three pepper species (74 samples) into three confidence intervals, indicating that PCA analysis could effectively distinguish the three pepper species. The shape of the C. annuum fruit was mostly short horn and C. frutescens species tended to be long finger, and these are inconsistent with previous studies [34,35]. This may be due to the difference in the genotype and growth environment of the pepper resources studied in this study from those previously studied [4,37]. The reported literatures demonstrated that C. annuum varied more than the other species in terms of fruit weight, length, and diameter [32,38,39] and our work strengthened this argument. However, it was interesting that the longest fruit (S71, C. annuum) was longer than those in previous reports [40,41]. Additionally, the pepper germplasms employed in this study were morphologically differentiated, which was attributed to the variation coefficients of greater than 39%, including fruit weight, length, and diameter (Supplemental Table S2). Early research described a negative correlation between fruit size and capsaicin content [32,34]. However, a weakly negatively correlation was proved in our work with respect to the morphological indicators (weight, length, and diameter) of C. annuum and capsaicin content (r < −0.28, p < 0.05).
The nutrients in peppers mainly include vitamins, carbohydrates, proteins, and capsaicin [4,14]. Chemical profiles were critical to the overall sensory quality of fruits, such as total soluble solids, soluble sugar, ascorbic acid, or titratable acidity, and could be employed to determine the ultimate application and the preferable market for pepper commercialization [42,43]. It was well known that total soluble solids, the soluble sugar, ascorbic acid and titratable acidity increase as maturation progresses of pepper fruits [8,43]. Those compounds investigated in this study were both significant differences that were intra-specific and interspecific of peppers, of which the most significant between species were found in total soluble solids and soluble sugars.
It has already been confirmed that fruit color was affected by the composition and concentration of carotenoids (capsanthin, zeaxanthin, β carotene) and anthocyanins (delphinidin), which were very important substances in the peel of pepper [13,14,44]. The fruits of Capsicum spp. have various fruit colors, e.g., light green, green, purple, yellow, orange, and red [13,18,35]. The red pepper peel was associated with capsanthin content, the yellow with zeaxanthin and beta carotene content, and the purple with anthocyanin, respectively [13,18]. This study found that some yellow-green and other colored fruits also contained high carotenoid concentrations, whereas some dark green fruits also contained high delphinidin concentrations (Table 1 and Supplementary Table S1). In other words, the contents of carotenoid and anthocyanin were inconsistent with fruit color in some cases. This may be due to the masking effect of chlorophyll in pepper fruit [45]. In fact, pepper fruits often contain a variety of pigmented substances that affect the final color of the peel.
Research on capsaicinoids could lead to better use of pepper for food (formation of spicy taste), pharmaceuticals (antibacterial, anti-inflammatory), and industrial products (source of pigment) [6,32,45,46]. Currently, published data have proved that the concentration of capsaicinoids in C. chinense peppers was higher than that in other species [10,31,47], and our work provided clear support for this point. The wide variety among different accessions in capsaicinoid concentrations may be explained by differences in genotype, environmental conditions, cultivation and crop management, fruit maturity, and harvest time [47]. Of the fatty acids, C16:1 concentration was of the greatest importance for capsaicin, dihydrocapsaicin, and nordihydrocapsaicin. It was reflected in significant positive correlations between the concentration of C16:1 and that of capsaicin, dihydrocapsaicin, and nordihydrocapsaicin, suggesting that C16:1 may play an important role in the biosynthesis of these three capsaicinoids.
Many studies argued that there were significant positive correlations between the concentrations of capsaicin and dihydrocapsaicin and those of many fatty acids, which also indicated that the biosynthesis of capsaicins was related to that of fatty acids [9,48]. Moreover, the results showed that the main fatty acids in pepper were C14–C24 fatty acids, which could be explained in two ways that were not mutually exclusive: (1) C8–C13 fatty acids were the precursors of capsaicin synthesis in pepper [49], and (2) most of the C8–C13 fatty acids are involved in the synthesis of capsaicin.
In conclusion, the results of this study could provide an available theoretical basis for the identification and breeding of pepper germplasm resources.

5. Conclusions

The results of the work showed that there were significant differences in the quality of the fruits of different pepper accessions. From the perspective of morphological characteristics (fruit type, fruit color, fruit size, etc.), C. chinense, C. frutescens, and C. annuum accessions exhibited different levels of variation. Capsaicin and dihydrocapsaicin were the most important capsaicinoid substances in pepper fruits, of which C. chinense had the highest concentrations, whereas some accessions of C. annuum were not detected. The higher carotenoids were tested in orange and red peppers, whereas the higher anthocyanins (specifically, delphinidin) were found in purple and black peppers. The pepper fruits investigated in this work were rich in the fatty acid, linoleic acid, oleic acid, and palmitic acid. Therein, linoleic acid (a polyunsaturated fatty acid) was the main fatty acid present in peppers. Seventy-five accessions were identified in this study, of which four accessions had the highest content of quality-related compounds. Two of them belonged to C. chinense (S23 and S24) and possessed high capsaicin concentration. However, S67 (C. annuum) had high β-carotene concentration and S68 (C. annuum) contained high levels of total fatty acid and ascorbic acid. In view of the important roles of capsaicinoids, carotenoids, and fatty acids in food and health, many of the pepper accessions identified in this study were rich in these phytochemicals, and may shed light on development potential.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/app12126292/s1, Table S1: Morphologic parameters among 75 pepper germplasm resources; Table S2: Variation of 75 pepper germplasm resources; Table S3: Morphologic parameters and chemical parameters among three Capsicum species; Figure S1: The investigated 75 peppers germplasm samples; Figure S2: HPLC chromatogram of ascorbic acid of standard (A) and sample S28 (C. annuum); Figure S3: HPLC chromatogram of capsanthin, zeaxanthin, and β-carotene of standard (A) and sample S40 (C. annuum); Figure S4: HPLC chromatogram of nordihydrocapsaicin, capsaicin, and dihydrocapsaicin of standard (A) and sample S24 (C. chinese); Figure S5: HPLC chromatogram of anthocyanidins of standard (A) and sample S34 (C. annuum); Figure S6: HPLC chromatogram of fatty acid methyl ester of standard (A) and sample S09 (C. annuum); Figure S7: Correlation heat map of quality-related indicators in the C. annuum (67 accessions). Blue means negative correlation, red means positive correlation. The depth of the color represents the level of correlation (the higher the correlation, the darker the color). The size of the circle also indicates the level of the correlation coefficient, and the higher the correlation coefficient, the larger the circle. If the p value is greater than 0.05, there is no circle display.

Author Contributions

Conceptualization and methodology, K.Z., J.W. and M.D.; writing—original draft preparation, P.L., Y.L. and X.Z.; writing—review and editing, J.L.; project administration, Z.X. and R.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (32160708), the Major Science and Technology Projects in Yunnan Province (202102AE090005, 202205AR070001), the Rural Revitalization Science and Technology Project in Yunnan Province (202204BI090004).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Cluster heat map of quality-related indicators in the 75 pepper germplasm resources.
Figure 1. Cluster heat map of quality-related indicators in the 75 pepper germplasm resources.
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Figure 2. Correlation heat map of quality-related indicators in the 75 pepper resources. Blue means negative correlation, red means positive correlation. The depth of the color represents the level of correlation (the higher the correlation, the darker the color). The size of the circle also indicates the level of the correlation coefficient, and the higher the correlation coefficient, the larger the circle. If p value is greater than 0.05, there is no circle display.
Figure 2. Correlation heat map of quality-related indicators in the 75 pepper resources. Blue means negative correlation, red means positive correlation. The depth of the color represents the level of correlation (the higher the correlation, the darker the color). The size of the circle also indicates the level of the correlation coefficient, and the higher the correlation coefficient, the larger the circle. If p value is greater than 0.05, there is no circle display.
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Figure 3. Principal component analysis of quality indicators of 75 pepper germplasm resources. (A) The PCA score plot in the space of the first 2 PCs explaining 45.9% of the total variance, and (B) the corresponding loadings plot. Sample number as shown in Table 1.
Figure 3. Principal component analysis of quality indicators of 75 pepper germplasm resources. (A) The PCA score plot in the space of the first 2 PCs explaining 45.9% of the total variance, and (B) the corresponding loadings plot. Sample number as shown in Table 1.
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Figure 4. Aggregated boosted tree (ABT) reflecting the relative effect of fatty acid concentrations on the concentration and composition of capsaicinoids in pepper fruit.
Figure 4. Aggregated boosted tree (ABT) reflecting the relative effect of fatty acid concentrations on the concentration and composition of capsaicinoids in pepper fruit.
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Table
Table 1. Concentrations of fruit metabolites among 75 pepper germplasm resources.
Table 1. Concentrations of fruit metabolites among 75 pepper germplasm resources.
No.SpeciesTotal Phenolics (mg/g)Total Soluble Sugars (mg/g)Total Soluble Solids (°Brix)Titratable Acidity (%)Total Soluble Protein (mg/g)Capsanthin (µg/g)Zeaxanthin (µg/g)β-Carotene (µg/g)Delphinidin (µg/g)Nordihydrocapsaicin (mg/g)Capsaicin (mg/g)Dihydrocapsaicin (mg/g)Ascorbic Acid (µg/g)
S01C. annuum3.42 ± 0.7833.89 ± 3.590.96 ± 0.030.32 ± 0.023.65 ± 0.25138.99 ± 56.1550.72 ± 1.824201.31 ± 980.04ND0.60 ± 0.050.98 ± 0.070.82 ± 0.05416.72 ± 86.24
S02C. annuum4.78 ± 0.586.90 ± 2.110.68 ± 0.120.25 ± 0.053.02 ± 0.44ND6.03 ± 1.55186.11 ± 54.83705.09 ± 147.690.70 ± 0.261.80 ± 0.581.24 ± 0.3949.20 ± 11.76
S03C. annuum4.40 ± 1.2728.50 ± 7.300.71 ± 0.100.38 ± 0.028.22 ± 0.21ND3.21 ± 0.20NDND0.66 ± 0.191.06 ± 0.241.27 ± 0.24594.37 ± 34.59
S04C. annuum4.82 ± 1.8912.31 ± 1.800.79 ± 0.030.41 ± 0.072.20 ± 1.00ND2.69 ± 0.212526.04 ± 40.46ND0.61 ± 0.080.80 ± 0.121.14 ± 0.111011.36 ± 50.65
S05C. annuum3.66 ± 1.2633.36 ± 28.740.85 ± 0.150.35 ± 0.023.07 ± 0.41ND37.96 ± 2.89307.08 ± 67.62247.63 ± 44.720.25 ± 0.030.93 ± 0.070.64 ± 0.05152.16 ± 16.13
S06C. annuum4.46 ± 0.3124.80 ± 7.420.42 ± 0.150.38 ± 0.028.74 ± 0.6254.17 ± 11.6513.91 ± 3.562045.06 ± 821.531183.52 ± 174.830.38 ± 0.051.90 ± 0.261.41 ± 0.206.68 ± 2.24
S07C. annuum2.58 ± 0.5439.01 ± 6.570.92 ± 0.040.34 ± 0.044.71 ± 1.21ND59.81 ± 11.75623.03 ± 39.98ND0.22 ± 0.050.88 ± 0.140.65 ± 0.09826.71 ± 22.97
S08C. annuum4.69 ± 0.3834.03 ± 6.560.87 ± 0.080.31 ± 0.034.89 ± 0.7649.91 ± 15.2646.83 ± 25.701737.28 ± 84.14ND0.37 ± 0.011.32 ± 0.020.92 ± 0.02465.84 ± 43.43
S09C. annuum2.57 ± 0.2560.14 ± 10.421.12 ± 0.080.27 ± 0.012.33 ± 0.71ND9.85 ± 0.94NDNDNDNDND390.68 ± 20.72
S10C. annuum2.82 ± 0.3723.38 ± 14.250.35 ± 0.050.25 ± 0.013.66 ± 0.48ND39.49 ± 4.57884.89 ± 105.11ND0.70 ± 0.260.73 ± 0.310.52 ± 0.2270.02 ± 46.92
S11C. annuum2.90 ± 0.5613.83 ± 0.360.88 ± 0.080.23 ± 0.014.30 ± 1.333.33 ± 0.6359.50 ± 17.971261.74 ± 265.55361.40 ± 53.360.23 ± 0.080.84 ± 0.230.66 ± 0.18475.04 ± 132.38
S12C. annuum3.10 ± 0.2731.58 ± 6.960.87 ± 0.230.31 ± 0.063.49 ± 1.778.02 ± 4.8065.29 ± 1.181597.91 ± 414.39368.82 ± 45.200.29 ± 0.040.79 ± 0.090.78 ± 0.093.53 ± 0.46
S13C. annuum3.21 ± 0.7443.54 ± 19.390.61 ± 0.200.44 ± 0.039.56 ± 1.433.90 ± 1.4750.19 ± 3.161021.12 ± 77.42245.65 ± 33.810.42 ± 0.061.10 ± 0.150.82 ± 0.11705.92 ± 95.78
S14C. annuum3.64 ± 0.4125.59 ± 1.560.77 ± 0.020.47 ± 0.0410.17 ± 0.36ND43.20 ± 18.221180.31 ± 556.21227.91 ± 18.090.36 ± 0.050.77 ± 0.110.73 ± 0.10607.65 ± 107.27
S15C. annuum4.36 ± 0.2921.72 ± 8.860.84 ± 0.150.30 ± 0.034.55 ± 0.646.41 ± 0.7574.40 ± 2.061813.75 ± 119.54257.93 ± 62.880.23 ± 0.071.04 ± 0.220.59 ± 0.1670.71 ± 24.51
S16C. annuum4.99 ± 1.1630.86 ± 2.060.77 ± 0.020.28 ± 0.012.21 ± 0.414.63 ± 0.3438.81 ± 6.891010.42 ± 84.58311.33 ± 14.800.22 ± 0.060.84 ± 0.180.67 ± 0.14164.52 ± 31.56
S17C. annuum2.37 ± 0.3010.00 ± 1.230.56 ± 0.030.28 ± 0.013.55 ± 1.554.98 ± 0.2644.04 ± 2.151019.60 ± 125.84276.70 ± 41.660.44 ± 0.081.25 ± 0.230.88 ± 0.16253.13 ± 68.05
S18C. annuum3.50 ± 0.5821.11 ± 0.910.43 ± 0.030.27 ± 0.011.38 ± 0.392.72 ± 0.776.75 ± 0.35158.26 ± 18.74302.65 ± 18.090.20 ± 0.021.13 ± 0.101.13 ± 0.1165.07 ± 11.97
S19C. frutescens3.24 ± 0.4112.94 ± 2.650.43 ± 0.010.26 ± 0.024.48 ± 0.55ND3.95 ± 0.81NDND0.53 ± 0.172.60 ± 0.702.00 ± 0.524.66 ± 0.74
S20C. frutescens3.83 ± 1.419.52 ± 0.560.38 ± 0.030.25 ± 0.021.45 ± 0.182.23 ± 0.076.85 ± 1.19180.22 ± 40.15ND0.48 ± 0.072.99 ± 0.281.60 ± 0.143.48 ± 1.59
S21C. annuum5.61 ± 0.8218.59 ± 0.540.61 ± 0.020.28 ± 0.011.47 ± 0.348.61 ± 1.3251.87 ± 8.61668.21 ± 30.16239.10 ± 25.800.32 ± 0.111.57 ± 0.390.93 ± 0.23243.04 ± 0.91
S22C. chinese3.27 ± 1.2127.20 ± 1.720.63 ± 0.020.25 ± 0.030.41 ± 0.355.55 ± 0.713.54 ± 0.29NDND0.24 ± 0.036.03 ± 0.313.14 ± 0.16991.58 ± 51.92
S23C. chinese2.76 ± 0.3727.23 ± 9.670.69 ± 0.080.22 ± 0.042.05 ± 0.5721.16 ± 11.819.57 ± 0.114815.45 ± 1177.86ND0.72 ± 0.0718.42 ± 1.758.55 ± 0.82519.77 ± 172.27
S24C. chinese12.13 ± 2.3137.93 ± 17.090.70 ± 0.160.28 ± 0.012.35 ± 0.6445.40 ± 5.0617.52 ± 2.375037.45 ± 1508.38ND1.83 ± 0.2022.96 ± 2.2613.86 ± 1.3636.68 ± 8.04
S25C. annuum2.98 ± 0.535.45 ± 3.170.39 ± 0.040.21 ± 0.050.77 ± 0.462.78 ± 0.763.31 ± 0.2380.79 ± 24.55NDND0.12±ND528.03 ± 81.38
S26C. chinese2.63 ± 0.2640.26 ± 16.830.83 ± 0.160.31 ± 0.071.02 ± 0.173.92 ± 0.444.17 ± 0.323027.86 ± 1421.84ND0.23 ± 0.036.59 ± 0.562.72 ± 0.23554.66 ± 86.26
S27C. annuum4.41 ± 0.2326.79 ± 2.390.65 ± 0.050.31 ± 0.021.23 ± 0.335.54 ± 2.4049.65 ± 8.661297.85 ± 292.36377.53 ± 40.010.34 ± 0.041.25 ± 0.140.83 ± 0.10108.64 ± 51.59
S28C. annuum3.95 ± 0.8824.39 ± 13.680.75 ± 0.350.39 ± 0.052.42 ± 1.614.46 ± 0.7244.28 ± 7.20979.17 ± 204.70264.45 ± 12.000.59 ± 0.041.53 ± 0.101.21 ± 0.08644.53 ± 59.14
S29C. annuum3.74 ± 0.5138.27 ± 2.271.06 ± 0.090.31 ± 0.034.66 ± 0.437.13 ± 2.2356.44 ± 3.651285.63 ± 141.90413.25 ± 163.360.29 ± 0.011.25 ± 0.021.04 ± 0.0143.22 ± 25.52
S30C. annuum3.99 ± 0.6212.41 ± 6.300.95 ± 0.050.36 ± 0.024.92 ± 1.1530.79 ± 4.6827.43 ± 12.891330.57 ± 203.62ND0.62 ± 0.071.89 ± 0.191.23 ± 0.13408.22 ± 184.52
S31C. annuum2.69 ± 0.9614.45 ± 0.960.58 ± 0.040.23 ± 0.042.55 ± 0.932.25 ± 0.576.71 ± 2.97224.90 ± 70.26ND0.11 ± 0.020.40 ± 0.050.29 ± 0.0420.32 ± 5.28
S32C. annuum3.62 ± 0.0537.21 ± 25.670.56 ± 0.050.28 ± 0.019.41 ± 0.192.85 ± 0.4713.71 ± 1.40363.58 ± 54.73211.97 ± 5.550.25 ± 0.011.32 ± 0.060.73 ± 0.038.33 ± 0.05
S33C. annuum2.54 ± 0.3733.82 ± 3.290.71 ± 0.250.26 ± 0.015.53 ± 0.313.34 ± 0.5944.93 ± 8.731162.24 ± 397.35247.79 ± 12.000.14 ± 0.060.77 ± 0.280.57 ± 0.2022.40 ± 10.94
S34C. annuum4.56 ± 0.4321.45 ± 2.770.60 ± 0.020.27 ± 0.023.70 ± 0.263.70 ± 0.6457.43 ± 11.401496.34 ± 399.63337.93 ± 49.020.25 ± 0.050.86 ± 0.140.71 ± 0.114.82 ± 0.96
S35C. annuum4.57 ± 0.3925.64 ± 0.180.57 ± 0.020.22 ± 0.031.05 ± 0.192.66 ± 0.2541.34 ± 1.721000.70 ± 7.05297.48 ± 47.030.19 ± 0.040.94 ± 0.180.64 ± 0.12265.03 ± 106.08
S36C. annuum3.67 ± 0.4617.15 ± 0.440.76 ± 0.040.32 ± 0.074.08 ± 2.304.96 ± 0.5939.11 ± 2.00947.66 ± 100.96287.98 ± 15.750.30 ± 0.031.27 ± 0.100.97 ± 0.08163.73 ± 33.59
S37C. annuum4.89 ± 0.4416.38 ± 5.930.80 ± 0.020.34 ± 0.022.81 ± 0.123.38 ± 0.6930.19 ± 3.66764.59 ± 46.00242.12 ± 24.930.45 ± 0.101.59 ± 0.251.36 ± 0.17290.41 ± 5.06
S38C. annuum3.97 ± 0.3449.45 ± 2.360.85 ± 0.030.20 ± 0.013.83 ± 0.984.82 ± 0.1451.53 ± 10.681294.95 ± 213.09265.83 ± 30.060.19 ± 0.000.72 ± 0.010.68 ± 0.0129.51 ± 24.13
S39C. annuum2.41 ± 0.7316.81 ± 6.540.83 ± 0.130.29 ± 0.062.14 ± 0.217.22 ± 1.0254.82 ± 0.401292.08 ± 13.13229.76 ± 32.890.25 ± 0.071.07 ± 0.270.88 ± 0.2246.33 ± 32.51
S40C. annuum3.68 ± 0.7216.06 ± 4.260.69 ± 0.070.24 ± 0.010.66 ± 0.174.29 ± 0.9343.29 ± 7.93986.07 ± 171.04303.72 ± 47.580.20 ± 0.030.86 ± 0.130.65 ± 0.09223.92 ± 7.52
S41C. annuum3.64 ± 0.4315.22 ± 2.090.47 ± 0.110.26 ± 0.021.02 ± 0.113.90 ± 1.1949.69 ± 15.961009.48 ± 200.54303.94 ± 18.570.53 ± 0.011.97 ± 0.031.38 ± 0.09154.49 ± 24.60
S42C. annuum2.85 ± 0.4031.48 ± 5.180.25 ± 0.030.23 ± 0.033.26 ± 0.784.69 ± 1.0453.26 ± 8.001096.17 ± 161.87265.68 ± 20.770.28 ± 0.010.84 ± 0.050.64 ± 0.0462.88 ± 3.70
S43C. annuum3.39 ± 0.3038.92 ± 26.070.83 ± 0.020.28 ± 0.016.36 ± 0.657.36 ± 2.83118.91 ± 2.372475.23 ± 195.81ND0.85 ± 0.052.29 ± 0.051.93 ± 0.044.76 ± 1.06
S44C. annuum3.33 ± 0.3844.69 ± 5.990.69 ± 0.110.27 ± 0.019.18 ± 0.3611.99 ± 1.5112.46 ± 2.382299.33 ± 372.61ND0.17 ± 0.021.04 ± 0.070.84 ± 0.06348.39 ± 97.58
S45C. annuum3.76 ± 0.5712.09 ± 1.950.58 ± 0.050.25 ± 0.012.42 ± 0.24ND48.09 ± 5.641231.07 ± 165.45240.58 ± 20.330.33 ± 0.061.75 ± 0.301.09 ± 0.17405.50 ± 251.74
S46C. annuum2.41 ± 0.3749.62 ± 1.420.76 ± 0.010.30 ± 0.036.84 ± 0.0915.21 ± 1.8319.21 ± 0.34646.41 ± 169.23ND0.10 ± 0.010.34 ± 0.030.20 ± 0.04769.21 ± 48.74
S47C. annuum4.48 ± 0.1854.75 ± 32.241.05 ± 0.150.34 ± 0.069.01 ± 2.5038.11 ± 3.0546.69 ± 7.91603.11 ± 250.06264.85 ± 52.080.35 ± 0.051.62 ± 0.220.99 ± 0.13904.82 ± 342.43
S48C. annuum3.29 ± 0.6632.90 ± 1.410.86 ± 0.070.45 ± 0.044.10 ± 1.224.58 ± 1.5547.95 ± 2.551183.36 ± 24.35250.38 ± 48.570.61 ± 0.051.36 ± 0.111.27 ± 0.07184.58 ± 74.58
S49C. annuum3.95 ± 1.2830.98 ± 12.090.97 ± 0.160.40 ± 0.013.44 ± 0.673.90 ± 0.3759.48 ± 10.511462.69 ± 16.09302.95 ± 25.590.29 ± 0.021.20 ± 0.050.98 ± 0.05857.24 ± 200.23
S50C. annuum1.90 ± 0.3317.10 ± 5.790.65 ± 0.060.25 ± 0.024.01 ± 0.4350.22 ± 9.4518.88 ± 5.481092.45 ± 404.37ND0.07 ± 0.000.26 ± 0.020.18 ± 0.02369.44 ± 102.68
S51C. annuum3.38 ± 0.1232.78 ± 8.080.90 ± 0.020.27 ± 0.014.92 ± 0.0112.22 ± 4.1486.94 ± 23.441739.75 ± 546.07ND0.92 ± 0.033.04 ± 0.101.83 ± 0.06715.06 ± 316.28
S52C. annuum3.78 ± 0.4622.90 ± 5.780.88 ± 0.210.38 ± 0.043.76 ± 1.1233.68 ± 17.2728.12 ± 1.641236.86 ± 49.00301.48 ± 3.760.25 ± 0.040.77 ± 0.080.63 ± 0.08710.83 ± 220.82
S53C. annuum3.92 ± 0.2610.00 ± 0.250.62 ± 0.030.37 ± 0.031.61 ± 0.12ND38.53 ± 6.98930.69 ± 134.94312.44 ± 51.440.27 ± 0.071.21 ± 0.310.72 ± 0.18378.99 ± 104.83
S54C. annuum2.82 ± 0.1014.88 ± 4.620.46 ± 0.060.29 ± 0.029.57 ± 0.09ND9.25 ± 1.83NDND0.37 ± 0.080.89 ± 0.160.91 ± 0.17812.04 ± 298.28
S55C. annuum4.04 ± 0.3116.33 ± 4.450.66 ± 0.050.34 ± 0.063.28 ± 0.3413.83 ± 5.4180.60 ± 7.741625.20 ± 677.81242.40 ± 3.070.29 ± 0.040.90 ± 0.120.67 ± 0.081029.64 ± 414.41
S56C. annuum3.35 ± 0.0323.06 ± 11.360.87 ± 0.120.29 ± 0.032.75 ± 1.063.97 ± 0.3744.07 ± 3.341014.19 ± 136.80321.01 ± 54.030.28 ± 0.100.83 ± 0.260.65 ± 0.20120.09 ± 31.62
S57C. annuum3.92 ± 0.3760.42 ± 7.810.98 ± 0.070.43 ± 0.046.75 ± 1.5461.21 ± 1.1669.91 ± 21.58701.40 ± 133.88278.51 ± 43.290.26 ± 0.060.92 ± 0.180.58 ± 0.11929.36 ± 268.77
S58C. baccatum2.65 ± 0.9023.57 ± 8.040.75 ± 0.170.23 ± 0.031.77 ± 0.692.49 ± 0.096.32 ± 1.62226.46 ± 74.47ND0.10 ± 0.020.58 ± 0.050.36 ± 0.03270.09 ± 72.14
S59C. annuum3.84 ± 0.7062.40 ± 7.870.81 ± 0.020.14 ± 0.023.32 ± 0.71170.92 ± 54.5643.17 ± 17.345278.37 ± 493.85ND0.02 ± 0.010.22 ± 0.010.12 ± 0.011517.32 ± 146.94
S60C. annuum4.95 ± 0.5154.55 ± 0.521.03 ± 0.060.63 ± 0.035.55 ± 0.9636.76 ± 7.5844.72 ± 1.171326.73 ± 76.88228.91 ± 26.030.38 ± 0.031.52 ± 0.080.97 ± 0.05784.88 ± 111.55
S61C. frutescens1.89 ± 0.0317.63 ± 8.410.53 ± 0.060.42 ± 0.051.96 ± 0.73ND4.06 ± 0.64107.70 ± 40.85ND0.04 ± 0.030.37 ± 0.050.21 ± 0.08277.86 ± 31.88
S62C. annuum4.23 ± 0.4619.36 ± 5.200.63 ± 0.080.32 ± 0.062.68 ± 0.30ND33.96 ± 1.92394.87 ± 89.31295.04 ± 85.270.32 ± 0.011.53 ± 0.050.92 ± 0.03673.38 ± 191.11
S63C. annuum3.52 ± 0.8430.88 ± 6.490.99 ± 0.210.42 ± 0.044.14 ± 2.1724.83 ± 8.9142.70 ± 9.70541.91 ± 98.93209.66 ± 1.170.37 ± 0.001.61 ± 0.020.77 ± 0.01648.36 ± 326.61
S64C. annuum2.31 ± 0.5822.63 ± 8.660.69 ± 0.040.28 ± 0.033.11 ± 0.514.37 ± 0.9841.01 ± 10.63949.32 ± 284.61249.30 ± 28.230.60 ± 0.091.71 ± 0.151.09 ± 0.075.44 ± 0.72
S65C. annuum3.93 ± 1.0339.88 ± 8.881.17 ± 0.050.27 ± 0.013.53 ± 0.6358.93 ± 29.0743.31 ± 7.362451.75 ± 398.86ND0.24 ± 0.020.88 ± 0.040.56 ± 0.031021.77 ± 349.44
S66C. annuum4.22 ± 0.5310.70 ± 1.910.73 ± 0.110.27 ± 0.017.16 ± 1.4621.86 ± 12.9167.17 ± 21.381595.52 ± 452.89365.09 ± 37.910.45 ± 0.071.67 ± 0.251.21 ± 0.1852.45 ± 21.71
S67C. annuum3.35 ± 0.1048.78 ± 9.650.81 ± 0.020.29 ± 0.042.31 ± 0.47116.37 ± 21.9468.64 ± 16.3411158.94 ± 845.46ND0.10 ± 0.010.67 ± 0.070.36 ± 0.04421.22 ± 183.19
S68C. annuum4.88 ± 0.3236.85 ± 3.031.34 ± 0.120.61 ± 0.064.49 ± 1.0751.75 ± 16.7132.93 ± 9.853761.49 ± 448.23NDNDNDND1102.40 ± 132.82
S69C. annuum6.12 ± 0.6411.49 ± 2.880.76 ± 0.180.43 ± 0.0110.62 ± 1.07ND25.37 ± 13.60ND2370.10 ± 380.840.29 ± 0.010.56 ± 0.010.37 ± 0.0185.83 ± 36.86
S70C. annuum4.41 ± 0.3611.18 ± 1.060.62 ± 0.210.21 ± 0.016.76 ± 0.762.44 ± 1.1014.94 ± 1.75546.00 ± 54.12830.16 ± 234.760.31 ± 0.031.58 ± 0.090.91 ± 0.05229.44 ± 112.52
S71C. annuum3.01 ± 0.4622.63 ± 4.190.60 ± 0.040.17 ± 0.015.93 ± 6.75ND21.66 ± 6.12405.09 ± 33.10805.71 ± 169.980.02 ± 0.000.24 ± 0.030.15 ± 0.02509.89 ± 224.37
S72C. annuum3.83 ± 0.3716.16 ± 7.900.72 ± 0.050.30 ± 0.064.56 ± 0.154.08 ± 0.8754.14 ± 10.241081.60 ± 233.36237.10 ± 5.560.40 ± 0.061.51 ± 0.251.29 ± 0.22766.56 ± 215.02
S73C. annuum4.56 ± 0.6315.77 ± 2.420.48 ± 0.100.27 ± 0.019.40 ± 0.27ND5.21 ± 0.50NDND0.73 ± 0.151.58 ± 0.201.41 ± 0.17241.55 ± 99.47
S74C. annuum3.93 ± 0.3349.91 ± 6.240.79 ± 0.200.40 ± 0.014.87 ± 0.695.09 ± 3.5756.37 ± 6.771325.14 ± 162.33245.87 ± 37.760.69 ± 0.032.12 ± 0.091.47 ± 0.06631.73 ± 218.25
S75C. annuum4.09 ± 0.5941.47 ± 2.271.11 ± 0.090.17 ± 0.033.92 ± 0.7271.87 ± 6.3511.57 ± 1.261092.92 ± 395.80ND1.25 ± 0.106.43 ± 0.103.18 ± 0.01494.16 ± 42.39
Table
Table 2. Fatty acid composition in 75 pepper germplasm resources (g/100 g of total fat).
Table 2. Fatty acid composition in 75 pepper germplasm resources (g/100 g of total fat).
No.C6:0C12:0C14:0C15:1C15:0C16:1C16:0C17:0C18:3n6C18:2n6cC18:1n9cC18:3n3C18:0C20:5C20:0C22:0C23:0C24:0Total SFAsTotal MUFAsTotal PUFAsTotal Fat (g/100g)
S010.24ND0.300.070.100.838.420.240.3869.5512.351.333.401.330.450.340.260.4014.1713.2572.594.40
S020.050.180.71ND0.060.386.450.15ND75.2110.921.073.210.460.380.320.110.3311.9611.3176.746.12
S030.040.040.41ND0.050.476.730.16ND80.907.091.221.830.280.240.190.110.2310.037.5682.418.93
S040.050.050.44NDND0.426.710.13ND80.827.181.181.810.330.230.270.120.2510.077.6082.347.01
S050.100.020.27ND0.060.538.190.170.2074.2611.531.201.810.740.340.240.090.2311.5412.0676.407.44
S060.110.130.62ND0.070.486.820.18ND78.788.461.251.400.730.310.230.140.2710.308.9580.765.62
S070.070.040.39ND0.060.357.360.140.1875.8511.031.081.820.640.330.270.130.2610.8811.3877.757.28
S080.040.040.390.050.050.487.130.140.1376.1810.241.172.670.370.380.230.060.2511.3810.7777.857.71
S090.010.080.44NDND0.286.470.09ND77.929.950.652.420.620.420.340.060.2510.5910.2279.199.73
S100.140.030.32NDND0.737.250.230.3073.3210.281.203.012.070.370.280.150.3112.0911.0276.894.24
S110.060.020.28ND0.060.407.320.160.1775.9510.581.072.560.530.300.27ND0.2711.3110.9877.728.54
S120.070.030.320.030.060.387.250.150.2674.5411.271.073.280.410.380.280.110.1112.0411.6776.288.84
S130.100.060.53NDND0.507.670.130.1473.8710.821.233.070.710.440.320.140.2812.7311.3275.957.44
S140.100.030.340.030.050.498.090.140.2271.0513.531.073.040.790.370.250.140.2712.8214.0573.137.97
S150.040.020.250.040.060.607.570.160.2176.359.921.092.390.470.320.230.060.2111.3110.5678.139.10
S160.68ND0.39NDND1.139.260.420.9261.1616.410.453.802.900.680.490.640.6717.0317.5465.431.80
S170.190.020.28ND0.070.647.920.190.4270.0513.311.123.251.340.430.270.150.3513.1213.9572.935.77
S180.110.020.32ND0.100.646.880.26ND75.628.941.053.131.090.380.380.200.4612.249.5877.764.86
S190.42ND0.45ND0.160.536.980.57ND74.608.210.824.101.050.730.590.240.5514.798.7476.472.74
S200.42ND0.42ND0.150.656.840.48ND73.968.550.904.271.140.800.480.300.6314.809.2076.002.69
S210.090.030.380.060.060.527.440.150.1970.5514.521.053.330.620.390.240.110.2512.4915.0972.427.35
S220.050.080.750.080.210.616.250.36ND69.6814.971.103.630.360.700.590.190.3813.1915.6671.154.23
S230.091.214.200.411.551.948.831.380.7451.9018.241.114.140.721.071.150.220.6924.5320.5954.472.88
S240.041.204.230.751.994.428.782.060.6547.4617.501.124.160.620.960.930.280.8025.4522.6649.852.86
S250.100.360.96NDND0.495.930.34ND74.1610.641.333.670.340.570.390.220.2712.8111.1375.833.42
S26ND0.291.540.060.450.337.920.51ND63.5916.971.054.190.660.770.770.300.5917.3417.3665.302.89
S270.240.030.38ND0.080.828.620.250.4965.0516.441.263.321.600.480.300.310.3214.3417.2668.404.40
S28NDNDNDNDND0.010.08ND0.010.660.150.010.030.020.01NDND0.010.140.150.703.01
S290.060.010.240.040.070.396.760.170.2278.298.871.052.500.470.280.210.090.2810.679.3180.029.36
S300.060.010.230.070.070.637.420.180.2276.259.931.142.290.740.270.190.090.2011.0310.6378.348.36
S310.150.030.41NDND0.346.710.19ND74.3610.320.954.130.990.440.350.170.4613.0310.6776.303.75
S320.39ND0.36ND0.160.698.590.38ND67.0213.940.943.671.210.530.760.430.9216.1914.6369.182.75
S330.230.020.31ND0.100.577.110.210.4972.1712.071.073.011.420.340.170.440.2912.2312.6475.144.13
S340.66ND0.41NDND1.168.440.360.6762.7516.181.113.592.380.660.480.580.5715.7517.3466.912.43
S350.35ND0.27NDND1.098.520.290.5067.5813.171.333.251.900.560.420.290.4914.4414.2671.312.92
S360.50ND0.33ND0.141.178.340.310.6066.2013.831.293.302.120.520.390.480.4714.7815.0070.222.63
S370.130.020.30ND0.080.656.640.230.1277.688.841.092.280.970.250.180.190.3310.649.4979.875.54
S380.58ND0.43NDND1.068.480.290.7562.6416.161.203.692.800.590.420.410.4915.3817.2267.402.54
S390.190.020.290.110.121.307.370.280.3871.9411.421.302.931.060.390.310.250.3412.4912.8374.674.39
S400.16ND0.30ND0.090.728.060.210.2972.0011.841.302.901.120.370.250.150.2512.7412.5674.702.93
S410.070.030.35ND0.060.537.780.140.1673.8911.561.202.560.840.280.210.080.2311.8112.0976.108.22
S420.150.030.37ND0.070.627.950.180.3471.1912.761.172.991.120.370.240.170.2812.8013.3873.826.50
S430.250.030.370.150.121.868.060.340.9963.3416.231.203.721.860.500.320.230.3114.2318.2467.393.86
S440.040.110.68ND0.050.388.010.15ND74.609.401.103.071.040.510.390.100.3713.489.7876.748.62
S450.070.030.370.050.060.607.370.200.2176.1710.541.081.680.690.330.230.100.2410.6711.1978.157.70
S460.170.140.66ND0.050.337.100.11ND77.648.651.112.080.930.300.320.100.3111.348.9779.689.17
S470.040.050.42NDND0.256.050.12ND78.238.930.993.170.520.510.41ND0.3011.079.1879.747.36
S480.110.030.41ND0.060.578.670.150.2067.8815.791.213.200.770.370.220.140.2213.5916.3570.067.16
S490.080.020.280.030.070.427.390.170.3075.1010.951.082.740.520.300.220.100.2411.6011.4077.007.64
S500.110.070.65NDND0.486.780.160.2374.9010.601.352.731.000.310.260.140.2411.4511.0777.485.00
S510.080.020.25ND0.060.577.32ND0.4573.7211.901.152.610.880.390.280.100.2411.3412.4776.197.88
S520.090.030.380.040.060.558.590.160.2369.3614.641.163.030.770.350.240.110.2313.2515.2471.517.44
S530.090.020.26ND0.060.578.010.180.2173.3911.201.192.960.820.370.290.090.2912.6211.7775.618.22
S540.070.070.520.020.060.356.870.18ND77.009.480.982.690.680.350.290.090.2811.489.8678.667.29
S550.070.030.37NDND0.548.160.160.4270.7114.131.082.640.850.310.210.090.2212.2614.6773.066.25
S560.150.020.27ND0.080.707.620.180.3672.8611.271.252.941.080.380.330.210.3012.4711.9775.565.29
S570.080.020.25ND0.070.557.280.130.2275.6810.151.202.870.550.330.250.110.2711.6610.7077.648.22
S580.120.020.44ND0.110.908.100.19ND67.6516.060.973.330.430.530.510.160.4713.9916.9669.054.96
S590.900.692.94ND0.090.5612.330.20ND59.5412.842.164.052.410.480.360.130.3122.4813.4064.114.24
S600.040.030.310.050.070.577.630.190.1774.0811.640.992.740.540.380.260.070.2311.9612.2775.778.07
S610.160.030.51ND0.111.018.400.20ND68.4114.720.913.160.450.580.630.180.5314.4915.7369.783.98
S620.100.020.270.050.080.497.220.190.1877.948.641.092.240.630.320.210.100.2410.999.1879.838.19
S630.040.020.260.060.070.647.830.180.2175.599.941.012.580.640.350.250.090.2511.9110.6377.469.30
S640.060.020.27ND0.050.537.890.150.1773.2112.091.192.531.010.320.240.080.1911.8112.6275.588.18
S650.050.050.410.040.050.517.940.110.2071.6914.271.132.420.490.300.20ND0.1511.6814.8273.509.09
S660.070.040.350.050.050.507.240.170.1973.4912.790.982.750.320.380.250.110.2711.7013.3374.978.82
S670.050.551.81ND0.050.429.490.10ND64.2816.271.432.821.590.410.370.070.2816.0016.6967.317.98
S680.030.150.80NDND0.276.690.10ND77.639.65ND2.501.080.380.370.060.2811.379.9278.7110.94
S690.050.040.33NDND0.257.040.140.1176.219.950.983.200.490.430.390.080.2912.0110.2177.799.74
S700.050.080.44ND0.050.326.700.13ND78.118.791.092.610.430.410.350.110.3111.259.1279.638.53
S710.060.300.98NDND0.316.380.13ND75.809.601.183.370.650.400.360.200.2812.469.9177.634.92
S720.050.020.220.040.050.377.670.160.1576.6510.51ND2.660.480.350.260.070.2711.7910.9377.299.74
S730.200.030.310.130.111.107.110.31ND73.9010.311.283.070.760.350.310.210.4112.4211.5475.945.00
S740.080.050.380.070.080.727.390.18ND76.209.271.142.870.570.400.230.090.2812.0310.0677.918.14
S750.100.060.32ND0.061.726.020.160.2278.278.531.421.800.500.290.260.090.199.3510.2580.407.67
Values are average of duplicates; ND—not detected.
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MDPI and ACS Style

Li, P.; Zhang, X.; Liu, Y.; Xie, Z.; Zhang, R.; Zhao, K.; Lv, J.; Wen, J.; Deng, M. Characterization of 75 Cultivars of Four Capsicum Species in Terms of Fruit Morphology, Capsaicinoids, Fatty Acids, and Pigments. Appl. Sci. 2022, 12, 6292. https://doi.org/10.3390/app12126292

AMA Style

Li P, Zhang X, Liu Y, Xie Z, Zhang R, Zhao K, Lv J, Wen J, Deng M. Characterization of 75 Cultivars of Four Capsicum Species in Terms of Fruit Morphology, Capsaicinoids, Fatty Acids, and Pigments. Applied Sciences. 2022; 12(12):6292. https://doi.org/10.3390/app12126292

Chicago/Turabian Style

Li, Pingping, Xiang Zhang, Yuting Liu, Zhihe Xie, Ruihao Zhang, Kai Zhao, Junheng Lv, Jinfen Wen, and Minghua Deng. 2022. "Characterization of 75 Cultivars of Four Capsicum Species in Terms of Fruit Morphology, Capsaicinoids, Fatty Acids, and Pigments" Applied Sciences 12, no. 12: 6292. https://doi.org/10.3390/app12126292

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