Mutation Associated with Orange Fruit Color Increases Concentrations of β-Carotene in a Sweet Pepper Variety (Capsicum annuum L.)

Pepper is the second most important vegetable crop in Bulgarian agriculture and has become the subject of extensive breeding programs that frequently employ induced mutagenesis. The success of breeding programs can be enhanced by the efficient and integral application of different biochemical and molecular methods to characterize specific mutant alleles. On the other hand, identifying new cost-effective methods is important under a limited-resources environment. In this paper we compare the levels of five health-related carotenoid compounds of fruits (alpha-carotene, beta-carotene, lutein, beta-cryptoxanthin, zeaxanthin) between a mutant variety Oranzheva kapia (possessing high ss-carotene concentration) and a corresponding initial pepper variety Pazardzhishka kapia 794. Both varieties are intended for fresh consumption. Pepper is a major natural source of beta-carotene. It was observed that fruit at both commercial and botanical maturity from mutant variety had greater alpha-carotene and beta-carotene concentrations to the initial variety (7.49 and 1.94 times higher, respectively) meaning that the mutant was superior in fruit quality to the initial genotype. Two hydroxylase enzymes, converting alpha- and beta-carotene to lutein and zeaxanthin, respectively, are known to exist in pepper and are encoded by two genes on chromosomes 3 and 6-CrtZ(chr03) and CrtZ(chr06). The molecular characterization of the mutant variety through locus-specific Polymerase chain reaction amplification, gene cloning and sequencing as well as expression was performed. Our results suggest that the increased ss-carotene accumulation in the mutant variety Oranzheva kapia results from a biosynthetic pathway breakdown due to deletion of CrtZ(chr03) gene.

Automated summary

Pepper is the second most important vegetable crop in Bulgarian agriculture and has been extensively bred through induced mutagenesis. A comparison of a mutant variety and its initial variety showed that the mutant had higher levels of alpha-carotene and beta-carotene, indicating superior fruit quality. The increased accumulation of beta-carotene in the mutant variety was attributed to a breakdown in the biosynthetic pathway due to the deletion of the CrtZ(chr03) gene.