Variation in Chromosome Number, Karyotype and Nuclear DNA Content of Five Species of Indian Typhonium Schott. (Araceae)-A Medicinally Important Plant

Abstract

Summary Detailed karyotype analysis of somatic chromosomes in 5 species of Typhonium Schott. of the family Araceae was carried out for the first time. The chromosome number varied from 2nϭ16 in T. flagelliforme to 2nϭ52 in T. diversifollium. Chromosome number 2nϭ18 and 2nϭ26 in T. trilobatum and T. roxburghii respectively suggest formation of anueploids during speciation. The asymmetric karyotype revealed structural alterations with 2 distinct types of chromosomes (long and very short types) as evident in different species of Typhonium. Significant variations in chromosome size were observed among the studied species. TF% revealed sub-metacentric long chromosomes in T. flagelliforme (TF value, 33%) and metacentric short chromosomes in T. diversifolium (TF value, 41%). Average chromosome length varied from 2.03 mm in T. diversifolium, a high altitude species (5000-7000 ft), to 8.68 mm in T. flagelliforme, a low land species (70-250 ft). Significant variations were observed in Interphase Nuclear Volume (INV) which varied from 142.05 mm 3 in T. trilobatum to 335.02 mm 3 in T. flagelliforme; nuclear DNA content varied significantly from 0.199 pg in T. diversifolium to 0.833 pg in T. flagelliforme.Key words Chromosome number, Karyotype, Nuclear DNA, Typhonium.The genus Typhonium Schott. of the family Araceae comprises about 79 species distributed mostly in the south-east Asia and north-east Australia (Hay 1993). In India and Indo-Malesian region, the genus is represented by 16 species (Santapau and Henry 1973). While Typhonium divaricatum (Linn.) Decne occurs mainly in the Penninsular India, T. trilobatum (Linn.) Schott. and T. flagelliforme Decne are the commonly found species in Bengal, Bihar, Orissa and Coromandel coast.In T. trilobatum, somatic chromosomes 2nϭ18 was reported (Sharma and Mukhopadhyay 1965) and 2nϭ26 (Simmonds 1954) were reported with distinctly different morphological characteristics among the ecotypes. Taxonomical grouping of some members of Araceae i.e. genus Sauromatum and Lazarum into Typhonium (Hay 1993) was of interest to us. However such groups based on chromosomal parameters, their karyotypes are not available. This paper deals with detailed investigations on chromosome number their karyotype, interphase nuclear volume (INV) and in situ nuclear DNA content in 5 Indian species of Typhonium may provide insight into chromosome behavior and genomic characteristics during the evolution and speciation in this genus. Materials and methods PlantsTubers of 5 species of Typhonium were collected from varied ecological conditions and main-