Phytochemical Assessment of Native Ecuadorian Peppers (Capsicum spp.) and Correlation Analysis to Fruit Phenomics

Abstract

In this work, the impact of pepper (Capsicum spp.) fruits morphology on their composition for health-promoting compounds was investigated. For that purpose, pepper accessions from Ecuador, one of the hotspots in Capsicum's origin, were analyzed for ascorbic acid, polyphenols, capsaicinoids, and prevention of cholesterol oxidation. Plant and fruit phenomics were assessed with conventional descriptors and Tomato Analyzer digital traits. Significant differences among accessions and species revealed a large diversity within the collection. The Capsicum frutescens group displayed the highest levels of capsaicinoids, whereas the polyphenols shortly varied among the five domesticated species. Capsicum pubescens exhibited the lowest content of ascorbic acid. The conventional descriptors describing the magnitude of plants and fruits, as well as digital attributes under the categories of size, shape index, and latitudinal section, mostly explained the variance among Capsicum groups. Correlation test revealed that phytochemical components were negatively correlated with the morphometric fruit attributes, suggesting that huge fruits contained lower amounts of nutraceutical compounds. Multivariate analysis showed that parameters related to fruit size, shape, and nutraceutical composition primarily contribute to the arrangement of pepper accessions. Such results suggested that those traits have been subjected to higher selection pressures imposed by humans.

Keywords: Tomato Analyzer; ascorbic acid; capsaicinoids; conventional phenotyping; correlation analysis; nutraceutical compounds; polyphenols.

Figure 1

Box plot of biochemical parameters. Twenty-fifth percentile, median, 75th percentile, and range minimum-maximum. Outliers (white circle) were identified as 1.5 times the interquartile range. Different letters indicate significant differences at p < 0.05.

Figure 2

Bar plots of biochemical parameters expressed per region for C. annuum, C. baccatum, and C. chinense. Different letters indicate significant differences at p < 0.05. Only those parameters showing significant differences among regions are represented.

Figure 3

Pearson’s rank correlation coefficients between pairs of traits. Color intensity (right scale) and the size of the circles are proportional to the correlation coefficients. Significant correlations at p < 0.05 are indicated with a white asterisk inside the circle.

Figure 4

Scatter plot of the principal component analysis (PCA) analysis for forty-two Ecuadorian pepper landraces. (A) Principal Component 1 (PC1) vs. PC2; (B) PC1 vs. PC3. Secondary axes show the factor loadings values. Traits with the highest factors for each component are represented.

Figure 5

Cluster analysis (Ward coefficient) based on four biochemical traits, four conventional fruit descriptors, and eighteen TA attributes for the forty-two Ecuadorian accessions. The color code matrix represents the variables standardized to z-scores. Letters in brackets indicate the Capsicum species (A = C. annuum, B = C. baccatum, C = C. chinense, F = C. frutescens, P = C. pubescens).

Figure 6

Geographical distribution of Ecuadorian pepper accessions. Provinces colored in white represent the Andes, those in grey the Coast, light grey the Amazon and dark grey the Austro.