Identification and validation of SNPs in the phytoene synthase 2 (psy2) gene associated with yellow color of the root in cassava (Manihot esculenta Crantz) accessions of the Brazilian Amazon

The biofortification of cassava ( Manihot esculenta Crantz) roots is one of the actual goals of genetic breeding, with the development of roots richer in carotenoids. In order to evaluate the natural genetic variation of cassava, this study analyzed 78 accessions from the Brazilian Amazon to verify the presence of single nucleotide polymorphism (SNP) molecular markers in the phytoene synthase 2 ( psy2 ) gene associated with root color. From the sequencing of 294 bp containing part of the intron 2 and the exon 3 of the psy2 gene, three SNPs located in the coding region and the existence of eight haplotypes were identified. The c.1434G > C (SNP1) and c.1485C > A (SNP3) variations were found in yellow and cream root accessions and nucleotide polymorphism resulted in amino acid substitution. SNP2 (c.1462T > C) was identified in accessions with white roots and its allelic variation did not result in amino acid substitution. Four haplotypes that presented SNP3 were widely distributed in the states of Pará, Amapá, Rondônia and Amazonas. All accessions of yellow or cream root that presented the SNP3 were in heterozygosity, confirming the dominance of the SNP, except for one accession, that could be used in genetic breeding. The effect of mutations on the structure and function of PSY2 was in silico evaluated by molecular dynamics and it was indicated that the aminoacid substitutions affected the active site of the protein depending on the distance. The results were compatible with the phenotype detected experimentally.