Karyomorphological analysis of different varieties of Tabernaemontana coronaria

Abstract

Tabernaemontana coronaria of Apocynaceae is an economically important medicinal plant, distributed throughout the tropics of the world. The different alkaloids produced by this species are effective against various disorders like abdominal tumors, asthma, diarrhoea, epilepsy, eye infections and fever. Morphological characters including internode length, petiole length, leaf area and leaf index varied between these varieties. Cytological analysis revealed three diploid varieties with 2n=22 chromosomes (Wild type T. coronaria, T. coronaria var. Variegata, T. coronaria var. Dwarf) and a triploid variety with 3n=33 chromosomes (T. coronaria var. Florepleno). A variation was recorded in total chromosome length and volume among the diploid varieties of T. coronaria. Most of the centromeric chromosomes were either median or median region. The present study indicated that cryptic structural changes of chromosomes might be responsible in the evolution of different varieties of T. coronaria except the Flore-pleno variety. Moreover, differential condensation of chromosomes attributing to variable chromosome length and volume has been suggested.