Genetic diversity and alkaloid production in Catharanthus roseus, C. trichophyllus and their hybrids

Inter and intraspecific variation was analyzed in two Catharanthus species with regard to isozyme polymorphism and indole alkaloid content in roots and leaves. No significant differences in alkaloid production were observed in three groups of C. roseus plants individualized for their flower color. Conversely, comparisons between C. trichophyllus and C. roseus, showed large differences of alkaloid profiles in both roots and leaves. Specific isozyme markers on four presumed loci were found allowing us to establish that natural hybridizations could occur between the two species when grown together. Experimental hybridizations confirmed that introgressions were feasiblebut suggested that a reproductive barrier was acting and involved interspecific incompatibility. The identification and assay of the main alkaloid compounds in natural interspecific hybrids displayed such a high hybrid vigor that interspecific hybridization may present a new and successful way of improving alkaloid production in Catharanthus species.