Detection and mapping of quantitative trait loci for the contents of the terpenoid indole alkaloids, vindoline and catharanthine, in the leaves of Catharanthus roseus using bulk segregant analysis

Abstract

A mapping population consisting of 191 F2:7 recombinant inbred lines (RILs) of Catharanthus roseus was used for segregation analysis of DNA markers, leading to the construction of a genetic linkage map of 174 DNA markers placed on eight linkage groups (LG). These markers were present at an average inter-marker distance of 10.2 cM. Leaves harvested from cultivated C. roseus plants are the main source of vindoline (V) and catharanthine (C), which are chemically condensed during commercial synthesis of the widely-used anti-cancer drugs, vincristine and vinblastine. To detect and map the major genes/quantitative trait loci (QTL) that control the accumulation of V and C in C. roseus leaves, a bulk segregant analysis approach was used. The above mapping population of RILs was phenotyped for their leaf alkaloid profiles and the distributions of V and C contents were used to assemble two pairs of contrasting bulks of RILs, one each for V and C accumulation in extremely low or extremely high amounts. Primers for the 174 already- mapped markers were PCR amplified on the bulks. Among the markers that discriminated between the high-C and low-C bulks, and the high-V and low-V bulks, those that amplified all members of their specific bulk were identified. This led to the detection of two QTLs (V1 and V2) and their co-segregating/linked DNA markers for high-V content, and one QTL (C1) and its linked DNA markers for high-C content. These three QTLs were then mapped. V1 and V2 were observed to lie on LG1, and C1 was on LG6. The QTLs V1 and V2 had large additive effects. These, and C1, appear to be suitable for marker assisted selection.