Karyological relationships in Indian species of Drimia based on fluorescent chromosome banding and nuclear DNA amount

Abstract

The genus Drimia (syn. Urginea), commonly called squill, represents a species complex, infrageneric delimitation being ill-defined due to morphological variability, population variation within species and polyploidy. In the present study, fluorescent chromosome banding and measurements of nuclear DNA content by flow cytometry were performed in five Indian species of Drimia: Drimia indica, Drimia polyantha, Drimia razii, Drimia wightii and Drimia coromandeliana to elucidate taxonomic relationship and obtain possible insights into the evolutionary processes within this group. All taxa analyzed exhibited similar karyomorphology with subtle differences accounted by nucleolar chromosomes. Nuclear DNA content ranged from 20.41 pg/2C in D. polyantha to 40.80 pg/2C in D. coromandeliana and was positively correlated with chromosome number (r = 0.67, P = 0.02) and total diploid chromatin length (r = 0.59, P = 0.06). Fluorescent chromosome banding revealed the presence of CMA(+ve)/DAPI(-ve) signals associated with nucleolar chromosomes presumably coincident with NOR in all species and unique CMA(+ve) signals in diploid populations of D. indica. Satellite polymorphism between homologous NOR-bearing chromosomes was observed which supports hybrid origin of the taxon. UPGMA dendrogram and scatter diagrams based on karyological parameters indicated a close relationship of D. indica, D. razii and D. polyantha while D. wightii and D. coromandeliana appeared distant. D. wightii appeared more close to D. indica than to all other species based on genome size and karyomorphology. As a whole, D. indica showed high intra-specific variability with populations exhibiting intergrading characters with other species. In conclusion, it is likely that hybridization followed by reproductive isolation of polymorphic forms arising by adaptation to different ecological niches resulted in species diversification of Drimia in India, probably from a common ancestor similar to D. indica.

Flow cytometry – a modern method for exploring genome size and nuclear DNA synthesis in horticultural and medicinal plant species

“…Their report was supplemented by Gitaí et al (2014), who established the GS of 28 species from the family Bromeliaceae. Other horticultural genera on which systematic classification studies have been supported by GS measurements are the vegetables: Lactuca, Capsicum, Daucus (Koopman, 2000;Doležalova et al, 2002;Moscone et al, 2003;Tavares et al, 2014;Nowicka et al, 2016), ornamentals: Rosa, Galanthus, Hemerocallis, Agapanthus, Lilium, Passiflora, Nerine, Dahlia, Fuchsia, Hydrangea, Nasturtium, Penstemon, Anthurium, Tulipa, Drimia, Cotoneaster (Yokoya et al, 2000Saito et al, 2003;Duncan, 2003, 2006;Souza et al, 2004;Marasek et al, 2005;Temsch et al, 2008;Talluri and Murray, 2009;Morozowska et al, 2010;Mortreau et al, 2010;Broderick et al, 2011;Bliss and Suzuki, 2012;dos Santos et al, 2014;Abedi et al, 2015;Nath et al, 2015;Rothleutner et al, 2016), and orchard crops: Ribes, Malus, Crataegus, Mespilus, and Olea (Chiche et al, 2003;Talent and Dickinson, 2005;Tatum et al, 2005;Brito et al, 2008). Although it is usually difficult to conduct FCM analyses on medicinal and culinary species (see Introduction), assessment of 2C was recently completed for: Curcuma, Salvia, Gentiana, Thymus, Ocimum, and 66 traditional Chinese medicinal species (Leong-Škorničková et al, 2007;Maksimović et al, 2007;Mishiba et al, 2009;Carović-Stanko et al, 2010;Koroch et al, 2010;Mahdavi and Karimzadeh, 2010;Zhang et al, 2013;…”

Fluorescent Chromosome Banding and Genome Size Estimation in Three Species of <i>Swertia</i>

“…Chromosome morphometric data were taken from at least five different metaphase plates from three individual plants of each species to construct karyotypes. Giemsa stained slides were destained in 70% methanol for subsequent staining of chromosomes with basespecific fluorochromes 4′-6-diamidino-2-phenylindole (DAPI) (AT-specific) and chromomycin A 3 (CMA) (GCspecific), following the protocol of Schweizer (1976) with minor modifications (Bhowmick et al 2012, Jha and Yamamoto 2012, Nath et al 2015. Chromosomes were stained with 50 µg mL 1 DAPI solution with Actinomycin D as a counterstain and observed under fluorescent microscope Zeiss Axioscop 2 with a UV filter cassette.…”

“…Based on conventional methods, S. chirayita and S. nervosa revealed an overall similarity in chromosome features while S. bimaculata had some differences in chromosome size and karyotype. There are many scopes to investigate chromosomal physiognomy based on advanced cytogenetic methods and fluorochrome banding analysis (Bhowmick et al 2012, Jha and Yamamoto 2012, Nath et al 2015. Especially the implication of enzymatic maceration and air drying technique (EMA, Fukui 1996) can potentially aid karyotype analysis following fluorochrome staining of chromosomes.…”

Chromosomal localization of 45S rDNA, sex-specific C values, and heterochromatin distribution in Coccinia grandis (L.) Voigt

“…Sex chromosomes have been distinctly identified through FISH with 45S rDNA as probes in animals and few plant species (Nakayama et al 2001;Lan et al 2006;Novotná et al 2011;Takehana et al 2012;Deng et al 2012). Simultaneously, variation in genome size is considered as an informative cytogenetic and taxonomic marker, employed in consolidating knowledge on species relations and cytogenetic evolution (Kron et al 2007;Nath et al 2014). Chromosomal distinction between male and female plants of C. grandis can be targeted through physical localization of 45S rDNA sequences.…”