3D Somatic Karyotype Analyses in Carthamus tinctorius

Abstract

Summary Karyomorphological investigation have been carried out in ten different accessions of Carthamus tinctorius belonging to the tribe Cynareae (thistle), sub-family Tubifloreae of family Compositae. For concrete studies we explored the details of 3D karyotype using length and volume of the chromosomes and the chromosome complements, in addition to several other related parameters. The observations show variability pertaining to length and volume as well as morphology of chromosomes indicating the structural chromosome polymorphism. All the accessions possessed 2nϭ24 and symmetrical or slightly asymmetrical karyotype. The accessions belonging to the same species were showing intra-specific and inter-specific chromosome polymorphism. Key words CarthamusThe genus Carthamus L. belonging to the tribe Cynareae (thistle), sub-family Tubifloreae of family Compositae has about 42 species with varying chromosome number of 2nϭ20 to 2nϭ64 and has a wide range of adaptation. C. tinctorius, commonly called safflower, is the only cultivated species of this genus. Commercially produced safflower seeds contain 32 to 52 percent oil. It is one of humanities oldest crop cultivated in India mainly for oil from the seeds and reddish and yellow dyes for clothing and food preparation from the flowers. The somatic chromosome analysis of the genus Carthamus is very difficult due to poor stainability, stickiness and tendency to overlap at metaphase and diffuse appearance of primary and secondary constrictions of the chromosomes. Three dimensional somatic karyotype were analyzed for establishing the chromosome and karyotype polymorphism. Materials and methodsThe present paper describes the three dimensional karyotypic analysis of different accessions of Carthamus tinctorius. The accessions that were used for somatic karyotype are listed in Table 1.For investigating the somatic karyotype, roots were first pre-treated with 0.05% colchicine solution for about 3 to 4 h at 10°C in darkness. The roots were then washed thoroughly with water and fixed in 3 : 1 absolute ethanol and glacial acetic acid having a pinch of ferric chloride. The fixed root tip samples were stored in 70% ethanol in refrigerator. The root tips were smeared and squashed in 1% aceto orcein. Karyotypic analyses in cells exhibiting C-metaphase were performed in such temporary preparations. The somatic chromosomes were analysed from the photomicrographs using computerized Nikon Image Capturing system. The following parameters were used for the somatic karyotype analyses.(a) Length of long arms, short arms and the whole chromosome, (b) arm's ratio, (c) total length of long arms (TLLA), all short arms (TLSA) and the whole chromosome (TLCC), (d) gradient index (GI), (e) symmetry index (SI), (f) radius of a chromatid of the chromosome of a complement and (g) total volume of long arms (TVLA), total volume of short arms (TVSA) and the whole