Characterization and genetic linkage mapping of the horticulturally important mutation leafless inflorescence ( lli) in periwinkle Catharanthus roseus

Abstract

Catharanthus roseus is a seasonal to perennial garden plant and the exclusive source of the anticancer drugs vincristine and vinblastine. Its horticultural importance is due to the compound racemose inflorescence architecture of branches in which pairs of prominent flowers are subtended by one of the two leaves per node. Here is reported the construction of a molecular framework genetic linkage map and mapping on it of the LEAF-LESS INFLORESCENCE ( LLI) locus. It is quantitatively shown that the adult lli mutant plants produce altered inflorescence of improved horticultural value, wherein axes are excessively branched, two flowers are formed per node that are bare of subtending leaves, and several times more open flowers are displayed each day, as compared to LLI plants. Segregational analysis of 914 PCR-based polymorphic markers identified 564 of them that segregated according to monogenic 1:1 ratio among 191 F 2:7 recombinant inbred lines of a mutant mapping population. The linkage analysis of 564 DNA markers gave a map in which 84 RAPD, 11 ISSR and 39 SSR (anonymous) markers and 8 microRNA and 30 EST-SSR (coding region) markers were organized into 8 linkage groups (LGs). All LGs contained 2–20 microsatellite markers. The framework map spanned 1790.4 cM and intermarker distance was 10.3 cM. While known primers/primer pairs were used to develop RAPD, ISSR, SSR and microRNA markers, the EST database of the species was mined for EST-SSR markers. EST-SSR resources developed in the study have added to the existing repertoire of microsatellites in C. roseus. The lli locus mapped to a 3.9 cM interval in the middle of LG4 flanked by microsatellite markers.