Candidate Gene Analysis for the Genes Controlling the Yellow Color in Capsicum annuum Cultivar MicroPep

Abstract

Carotenoids are major pigments coloring yellow, orange and red in plants. In Capsicum, phytoene synthase (PSY), capsanthin-capsorubin synthase (CCS), β-Carotene hydroxylase (Crtz-2) and lycopene β-cyclase (Lcyb) were identified to be involved in the carotenoid synthesis pathway. Orange and yellow colors in pepper can be resulted from mutations in these four genes but the relationship between the colors and the four candidate genes has not been fully elucidated. We examined these four carotenoid biosynthesis genes and measured the carotenoid contents of C. annuum MicroPep Red (MR), MicroPep Yellow (MY) and their F2 population. MicroPep lines have dwarf phenotypes. Mutation of the two candidate genes, PSY and CCS, were identified in the MY line. These mutations of PSY and CCS genes cosegregated with the fruit colors in the F2 population with a phenotypic ratio of 9:6:1(red:orange:yellow). In the F2 population, red peppers (PSY/CCS) accumulate higher levels of total carotenoid than those of yellow peppers (psy/ccs). In the orange peppers, we were able to classify the carotenoid content profile according to genotypes of PSY and CCS. Total carotenoid content in type 1 (PSY/ccs) was much higher than that in type 2 (psy/CCS) but capsanthin was accumulated more in type 2 than type 1. These results show that PSY and CCS genes affect the fruit colors of pepper in different ways in the carotenoid pathway. Moreover markers developed in this study can be used to distinguish the fruit colors of pepper.