Cytogenetical analyses of some species of the genus Sisymbrium (Brassicaceae) in Turkey

In this study, karyotype analyses of three species belonging to the genus Sisymbrium L. (Brassicaceae) and grown naturally in Turkey were conducted. These taxa are S. officinale (L.) Scop., S. runcinatum Lag. ex DC. and S. orientale L. The somatic chromosome number of 2n = 14 was reported for all species. Total chromosome lengths are between 1.33 and 2.43 μm in S. officinale, 1.30 and 2.48 μm in S. orientale, 1.02 and 2.18 μm in S. runcinatum. The karyotypes are as follows: S. officinale consists of 12m + 2sm, S. orientale consists of 10m + 4sm and S. runcinatum consists of 10m + 4sm chromosome pairs. S. runcinatum is the most asymmetrical karyotype based on all index values.


Introduction
The family Brassicaceae is the richest in the United States (616 species, 148 endemic) and the second richest in Turkey (606 species, 39 subspecies, 18 varieties, and 226 endemics) in terms of species number (Al-Shehbaz et al., 2007;Al-Shehbaz, 2010;Mutlu, 2012;Mutlu and Karakuş, 2015).Forty species belonging to the family Brassicaceae in Turkey were published as new species in the last decade (Mutlu, 2012;Mutlu and Karakuş, 2015), and this number has continued to increase.The family Brassicaceae has many species of economic importance and consumed as vegetables.These species are Brassica nigra (L.) Koch.(black mustard), Sinapis alba L. (gillyflower) is an important ornamental plant (Seçmen et al., 1998).

Materials and Method
The species were collected from different localities in Turkey.Collection information is listed below.Karyotypes analysis were carried on somatic metaphases using Image System Analysis.Root meristems from germinating seeds collected in the wild were used.Root tips were pretreated with α-monobromonaphthalene at 4°C for 16 h and were fixed with Carnoy for 24 h at 4°C.Before staining, the materials were hydrolyzed with 1N HCl for 12 minutes at room temperature, then stained with 2% acetic orcein and mounted in 45% acetic acid.Permanent slides were made by using the standard liquid nitrogen method.

S. officinale -A1
Photographs were taken through BX51 Olympus microscope.The ideograms were prepared with measurements taken on enlarged micrographs of ten well spread metaphase plates.The classification of chromosomes, the length of long and short arm, arm ratio, centromeric index and relative chromosomal length were measured by Software Image Analysis (Bs200ProP).Chromosomes were classified using the nomenclature of Levan et al. (1964).The karyotype asymmetry was determined as the interchromosomal asymmetry with parameters of Rec, A2 and CV CL and the intrachromosomal asymmetry with parameters of AsK, TF, Syi, A1, A and M CA (for details see Paszko, 2006;Eroğlu et al., 2013;Peruzzi and Eroğlu, 2013).

Sisymbrium officinale
The metaphase chromosomes and idiogram are shown in Figure 2a.The karyotype formula is 2n = 2x = 14 = 12m 2sm.The sixth chromosome pairs are submedian and the others are median as observed at mitotic plates.The total haploid length and mean haploid length of the chromosomes are 12.71 and 1.82 μm with single chromosome lengths ranging from 1.33 to 2.43 μm (Table 1).The intrachromosomal and interchromosomal asymmetry values are given in Table 2.

Sisymbrium orientale
The metaphase chromosomes and idiogram are shown in Figure 2b.The karyotype formula is 2n = 2x = 14 = 10m + 4sm.The second and third chromosome pairs are submedian and the others are median as observed at mitotic plates.The total haploid length and mean haploid length of the chromosomes are 12.84 and 1.83 μm with single chromosome lengths ranging from 1.30 to 2.48 μm (Table 1).The intrachromosomal and interchromosomal asymmetry values are given in Table 2.

Sisymbrium runcinatum
The metaphase chromosomes and idiogram are shown in Figure 2c.The karyotype formula is 2n = 2x = 14 = 10m + 4sm.The fourth and sixth chromosome pairs are submedian and the others are median as observed at mitotic plates.The total haploid length and mean haploid length of the chromosomes are 10.56 and 1.51 μm with single chromosome lengths ranging from 1.02 to 2.18 μm (Table 1).The intrachromosomal and interchromosomal asymmetry values are given in Table 2.

Discussions
Image Analysis System we used in this study made us to find the length of chromosomes and to compare different taxa more precisely.This system offers many advantages over conventional cytological and chromosomal techniques.It enables the analysis of a large number of chromosome spreads, saving the time and effort; besides, the accuracy of the data is high and the reproducibility of the image manipulation is complete and very sensitive helping to reduce error factor to minimal.

Species
All Sisymbrium species examined in the present study show a similar karyomorphology including only median and submedian chromosomes.According to literature survey, the cytological studies on Sisymbrium are generally related to the chromosomal counts.The report also confirm a similar karyomorphology including only median and submedian chromosomes for S. orientale and S. runcinatum from population of Libya (Kamari et al., 2015).Despite similar karyomorphology, the chromosome numbers are different between Turkey and Libya populations.
Karyotype asymmetry is an important parameter in karyological data (Eroğlu et al., 2013).S. runcinatum is the most asymmetrical karyotype based on all index values.However, the symmetrical karyotypes are different.While S. orientale is the most symmetrical karyotype in M CA , AsK, TF, Syi, A1 and A (intrachromosomal index values); S. officinale is the most symmetrical karyotype in CV CL , Rec and A2 (interchromosomal index values) (Table 2).
Karyological knowledge needs to be used in conjunction with other sources of data to achieve a better understanding of the cytological relationship of Sisymbrium species, leading to their natural classification.In this regard, karyotypes were determined in three species of Sisymbrium growing naturally in Turkey, and karyological attributes of selected species were evaluated for the first time.