Functional polymorphism in lycopene beta-cyclase gene as a molecular marker to predict bixin production in Bixa orellana L. (achiote)

Bixin is an apocarotenoid obtained from the seed aril of Bixa orellana L., a tropical plant known as achiote in Mexico. This compound is the second most commonly used natural colouring for food and pharmaceutical industries. B. orellana is an outcrossing species that displays high genetic variability. Recently, the colour traits of sexual organs were associated with the biosynthesis and accumulation of bixin in mature seeds. Herein, we describe a new approach for genotype–phenotype association by surveying lycopene beta-cyclase (Boβ - LCY1 ) gene variation in sixteen achiote accessions divided into three groups according to contrasting traits, such as flower colour, fruit colour and bixin production. Using a combination of single-strand conformational polymorphism techniques and the sequencing of polymorphic bands, we identified several single-nucleotide polymorphisms that divided the accessions into three haplotypes. Surprisingly, we observed that these three haplotypes were consistent with the same three groups previously characterized by phenotypic traits. We derived a putative sequence for the Boβ - LCY1 gene and surveyed the variations in this sequence. The heterozygosity of Boβ - LCY1 alleles resulted in a higher bixin content, likely associated with heterosis for this metabolite. These findings augment the toolbox available for the selection and genetic improvement of B. orellana and provide a reliable phenotype–genotype association method for commercial varietal selection, contributing to the development of laboratory techniques to identify desirable traits of commercial plant species.