Cytogenetical studies of some Convolvulaceae members from the Western Ghats, India reveal uniformity in karyotypes

Abstract

Karyotypes of six Ipomoea and one Merremia species were studied. Chromosome counts of 2n = 30 for I. corymbosa, I. kotschyana, I. marginata f. candida and M. rhyncorhiza) and 2n = 60 for I. ochracea were observed for the first time. Meiotic course of five Ipomoea species was also examined for the first time and two counts, i.e. n = 15 and n = 30 were recorded. Meiosis was found normal. Karyotypes of the studied species exhibited uniformity. All the species had chromosomes with median region centromeres and karyotypes were symmetrical (Stebbins’ 4A category). I. marginata f. candida had the shortest chromosomes with mean length of 0.99 ± 0.02 µm. I. ochracea and I. corymbosa had the longest chromosomes with mean length of 1.22 ± 0.05 µm and 1.22 ± 0.01 µm, respectively. As chromosomes were small and exhibited uniform morphology, fluorescent banding or fluorescent in-situ hybridization can be useful to differentiate the karyotypes and understand species interrelationships.