Comparative color and quality analyses of color mutants and wild-type of pepper at different developmental stages

In this study, the wild type 6421 and the fruit color mutant E55 of pepper were evaluated for fruit color, pigment contents and quality components at different developmental stages. The results demonstrated that the fruit color of 6421 and E55 changed from green to yellow and then to red, and from green to brown and then to orange, respectively, as the fruit developed from mature green to ripe. For both 6421 and E55, the color parameters a* and C* increased, while hue angle (h) value decreased. Furthermore, chlorophyll (Chl) content declined, whereas carotenoid (Car) content increased. Additionally, the contents of VC, soluble sugar, soluble protein and capsaicin increased, while cellulose content decreased. At the mature green stage, there was no significant difference between 6421 and E55 in five color parameters (L*, a*, b*, C*, and h values), Chl and Car contents or six quality indicators (cellulose, VC, soluble sugar, soluble protein, and capsaicin contents) (P > 0.05). During the color-turning to ripening stages, L*, b* and C* values and VC and soluble sugar contents were significantly higher and soluble protein and cellulose contents were significantly lower in E55 than in 6421 (p 0.05). Correlation analysis showed that for both 6421 and E55, Chl and Car contents were significantly or extremely significantly correlated with each quality parameter except for cellulose content. Among the tested quality indicators, soluble sugar, soluble protein, and capsaicin contents were significantly or extremely significantly positively correlated with each other, while cellulose content was significantly or highly significantly negatively correlated with the other indicators. This study can serve as a theoretical basis for research on the coloration mechanism of peppers as well as for the screening and breeding of high-quality pepper cultivars.