Introduction

Bell pepper (Capsicum annuum L.) is one of the most important vegetables consumed worldwide. Pepper is a diploid plant with 24 chromosomes (2n = 2x = 24). Its fruit contains a wide range of nutrients, vitamins, and bioactive pigments with significant health benefits. Carotenoids notably enhance the nutritional value of pepper. The carotenoids in pepper mainly consist of the highly stable capsanthin and capsorubin, along with β-carotene, β-cryptoxanthin, lutein, zeaxanthin, antheraxanthin, and violaxanthin. Xanthophyll pigments are mainly found in red peppers. The main carotenoids in fully ripened yellow/orange peppers include lutein, β-carotene, violaxanthin, antheraxanthin, zeaxanthin, and β-cryptoxanthin. Vitamin C, another nutrient and antioxidant, is present in some pepper varieties at concentrations twice as high as those in tomatoes, apples, or oranges per gram of fruit fresh weight. Anthocyanins, an important group of water-soluble pigments belonging to flavonoids, are widely distributed in plant organs, contributing to various colors such as red, blue, and purple. Anthocyanins possess biological functions that promote health, including antioxidant, anticancer, anti-aging effects, as well as protecting eyesight. Genetic diversity is a major prerequisite for any crop breeding program. The cultivated Capsicum species exhibit broad diversity due to evolution, domestication, and artificial selection. The genetic diversity of pepper germplasm resources is critical for ongoing research and breeding efforts. Plant breeders have employed diverse breeding techniques to improve economically important traits in peppers. Therefore, information about genetic diversity is essential for breeding programs. The main goal of the present study was to evaluate the diversity of quality traits and their genetic parameters among 80 inbred lines of bell pepper.

Materials and Methods

This study aimed to evaluate the genetic diversity of 80 bell pepper genotypes based on fruit quality traits. The experiment was conducted based on completely randomized design under greenhouse conditions at Shahid Bahonar University of Kerman. Quality traits were measured at both mature unripen and fully ripened fruits. Subsequently, genetic parameters such as genotypic and phenotypic coefficients of variation, genetic and phenotypic variance, broad-sense heritability, narrow-sense heritability, and response to selection were calculated. All data were subjected to analysis of variance (ANOVA) for different color groups of inbred lines. To assess genetic diversity among the lines, principal component analysis (PCA) was conducted. In addition, means were compared using Duncan’s mean comparison test.

Results and Discussion

Mean comparisons revealed that genotype 9 was one of the best lines in terms of ascorbic acid and photosynthetic pigment contents (chlorophyll a, chlorophyll b and total chlorophyll). Genotype 67 was the best line in term of anthocyanin accumulation in both mature unripen and ripened fruits. Genetic parameter analysis indicated that anthocyanin content in mature unripen fruits had the highest heritability and response to selection. The highest genotypic and phenotypic coefficients of variation were related to anthocyanin content in mature unripen and ripened fruits, respectively. ANOVA results among different cultivar groups based on fruit color showed significant differences for all measured traits, indicating sufficient diversity among the groups. The highest anthocyanin content was found in maroon ripened fruits (27.30 mg-1gFW). The highest and lowest vitamin C content in ripened fruits were observed in red and maroon peppers, respectively. The highest chlorophyll-a level was found in orange-colored fruits (0.63 mg-1gFW), while the lowest was observed in brown-colored fruits (0.41 mg-1gFW). Considering PCA results, the first two components explained 70.87% of the total variation. Biplot analysis divided the inbred lines into two groups. The smaller group included genotypes 50, 26, 41, 51, 81, and 65, which had low levels of photosynthetic pigments and high carotenoid content. High genetic diversity observed among the studied genotypes suggested that the potential for identifying promising inbred lines to improve hybrid breeding programs

Conclusion

This study was performed to assess the diversity of quality traits and their genetic parameters among several bell pepper inbred lines. The results exhibited a wide range of genetic diversity and high amount of heritability among studied lines. Significant differences were observed between the different color groups also showed proper diversity for almost traits between different colors. It seems that, there is a potential of identifying promising inbred lines among studied lines.