Comparative 1H NMR-Based Metabolomics of Traditional Landrace and Disease-Resistant Chili Peppers (Capsicum annuum L.)

Abstract

Chili peppers (Capsicum annuum L.) are economically valuable crops belonging to the Solanaceae family and are popular worldwide because of their unique spiciness and flavor. In this study, differences in the metabolomes of landrace (Subicho) and disease-resistant pepper cultivars (Bulkala and Kaltanbaksa) widely grown in Korea are investigated using a ¹H NMR-based metabolomics approach. Specific metabolites were abundant in the pericarp (GABA, fructose, and glutamine) and placenta (glucose, asparagine, arginine, and capsaicin), highlighting the distinct physiological and functional roles of these components. Both the pericarp and placenta of disease-resistant pepper cultivars contained higher levels of sucrose and hexoses and lower levels of alanine, proline, and threonine than the traditional landrace cultivar. These metabolic differences are linked to enhanced stress tolerance and the activation of defense pathways, imbuing these cultivars with improved resistance characteristics. The present study provides fundamental insights into the metabolic basis of disease resistance in chili peppers, emphasizing the importance of multi-resistant varieties to ensure sustainable agriculture and food security. These resistant varieties ensure a stable supply of high-quality peppers, contributing to safer and more sustainable food production systems.

Keywords: Capsicum annuum; Subicho; chili pepper; disease-resistant cultivars; landrace; metabolomics; multivariate analysis; nuclear magnetic resonance.

Figure 1

Representative ¹H NMR spectrum (800 MHz) of the pooled QC sample prepared by pooling equal volumes of all chili extracts.

Figure 2

OPLS-DA score plots derived from the ¹H NMR spectra (800 MHz) of each component in the pericarp, placenta, and seeds of the three cultivars (A). Corresponding loading of the scatter plot derived from targeted metabolite profiling (B). Thirty samples of each edible part were obtained (pericarp, ●; placenta, ■; seed, ▼), totaling 90 samples (n = 30).

Figure 2

OPLS-DA score plots derived from the ¹H NMR spectra (800 MHz) of each component in the pericarp, placenta, and seeds of the three cultivars (A). Corresponding loading of the scatter plot derived from targeted metabolite profiling (B). Thirty samples of each edible part were obtained (pericarp, ●; placenta, ■; seed, ▼), totaling 90 samples (n = 30).

Figure 3

OPLS-DA score plots derived from the ¹H NMR spectra (800 MHz) of the pericarp (A), placenta (B), and seed components (C) of the three cultivars. Ten samples of the three cultivars (Subicho, ●; Bulkala, ■; Kaltanbaksa, ▼) were obtained, totaling thirty samples (n = 10).

Figure 3

OPLS-DA score plots derived from the ¹H NMR spectra (800 MHz) of the pericarp (A), placenta (B), and seed components (C) of the three cultivars. Ten samples of the three cultivars (Subicho, ●; Bulkala, ■; Kaltanbaksa, ▼) were obtained, totaling thirty samples (n = 10).

Figure 4

OPLS-DA scores (A,C,E,G) and coefficient or loading plots (B,D,F,H) for metabolic differentiation between the Subicho and Kaltanbaksa pericarp components (A,B), Subicho and Bulkala pericarp components (C,D), Subicho and Kaltanbaksa placenta components (E,F), and Subicho and Bulkala placenta components (G,H) for identification of the chili pepper metabolites responsible for metabolic differentiation. The colors in the loading plot correspond to the correlation among variables. All OPLS-DA models were generated using one predictive and one orthogonal component. Their reliabilities and predictabilities are indicated by R²X, R²Y, and Q². Abbreviations of the names of the assigned metabolites are listed in Table S1. Ten samples were obtained from the edible parts of each cultivar (n = 10).

Figure 5

Quantification of individual metabolites in capsicum and comparison of the relative metabolite contents of the pericarp, placenta, and seed components of the three cultivars. Vertical bars denoted by different lowercase letters indicate significant differences between compounds at p < 0.05, as defined by Duncan’s multiple range test. Ten samples were obtained from the edible parts of each cultivar (n = 10). N.D. denotes values that were not detected. Different colored circles represent individual data points for each sample.