Distribution of 5S and 35S rRNA gene sites in 34 Chenopodium species (Amaranthaceae) BOZENA KOLANO 1 *, HANNA TOMCZAK 1 , RENATA MOLEWSKA 1 , ERIC N. JELLEN 2 and JOLANTA MALUSZYNSKA 1 1 Department of Plant Anatomy and Cytology, University of Silesia, Jagiellonska 28, 40-032 Katowice, Poland 2 Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602-5157, USA Received 13 September 2011; revised 17 May 2012; accepted for publication 8 June 2012 Studies on Chenopodium chromosomes are scarce and restricted mainly to chromosome number estimation. To extend our knowledge on karyotype structure of the genus, the organization of 5S and 35S rRNA genes in Chenopodium chromosomes was studied. The rDNA sites were predominantly located at chromosomal termini, except in a few species where 5S rDNA sites were interstitial. The majority of the diploid species possessed one pair each of 35S and 5S rDNA sites located on separate chromosomes. Slightly higher diversity in rDNA site number was observed in polyploid accessions. One or two pairs of 35S rDNA sites were observed in tetraploids and hexaploids. Tetraploid species had two, four or six sites and hexaploid species had six or eight sites of 5S rDNA, respectively. These data indicate that, in the evolution of some polyploid species, there has been a tendency to reduce the number of rDNA sites. Additionally, polymorphism in rDNA site number was observed. Possible mechanisms of rDNA locus evolution are discussed. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 220–231. ADDITIONAL KEYWORDS: chromosomes – fluorescent in situ hybridization – NORs – nucleolar organizing regions INTRODUCTION The genus Chenopodium L. includes c. 120 species, which are mostly colonizing herbaceous annuals occu- pying large areas in the Americas, Asia, Australia and Europe (Aellen, 1960; Jellen et al., 2011). Several species are of economic importance, either as prom- ising food sources or as noxious weeds. Chenopodium belongs to subfamily Chenopodioideae of Amaran- thaceae (Caryophyllales). The taxonomic history of Chenopodium is complex, and the most comprehen- sive treatments are those published by Aellen & Just (1943) and Aellen (1960). These divided the genus into 13 sections, some of which were further divided into subsections. In the late 1990s, a new system was devised by Mosyakin & Clemants (1996, 2002, 2008). The primary alteration in that system was the removal from the genus of the aromatic chenopods with glandular hairs as the distinct genus Dysphania R.Br. The hypothesis that the aromatic species are a distinct group was later supported by molecular phy- logenetic analysis (Kadereit et al., 2003, 2010). All phylogenetic studies indicated that Chenopodium is a polyphyletic genus (Kadereit et al., 2003; Muller & Borsch, 2005; Fuentes-Bazan, Mansion & Borsch, 2012). Recent analysis based on non-coding plastid and nuclear internal transcribed spacer (ITS) sequences showed that the genus consists of five major clades (Fuentes-Bazan et al, 2012). A separate clade was distinguished for aromatic chenopods with glandular hairs. The second clade, consisting of Chenopodium spp., related to C. capitatum (L.) Ambrosi and C. foliosum Asch. and Spinacia L. and two other genera of Chenopodioideae. Two other clades are composed of C. rubrum L. and relatives and C. murale L. and relatives. The fifth clade (Chenopodium s.s.) includes the crop species, such as *Corresponding author. E-mail: bozena.kolano@us.edu.pl Botanical Journal of the Linnean Society, 2012, 170, 220–231. With 2 figures © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 220–231 220 Downloaded from https://academic.oup.com/botlinnean/article/170/2/220/2416229 by guest on 28 December 2022