A comparative study of chromosome morphology among some accessions of Aegilops crassa

Department of Agriculture and Plant Breeding, Faculty of Agriculture, Maragheh University, Maragheh, Iran. Department of Agriculture, Faculty of Agriculture, Guilan University, Rasht, Iran. Department of Agriculture and Plant Breeding, Faculty of Agriculture, Mohaghegh Ardebili University, Ardebil, Iran. Department of Biotechnology, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran

Because of importance of genus Aegilops as a wild genetic source of wheat, some cytogenetic analysis reported (Chennaveeraiah, 1960;Badaeva et al., 1998Badaeva et al., , 2001) ) and indicated that all A. crassa chromosomes can be identified by their morphology and C-banding patterns.Cytogenetical studies have been carried out on A. crassa but a comparative study of chromosome morphology among accessions in A. crassa is not well documented.*Corresponding author.E-mail: hatamimaleki@yahoo.com.
Hence, cytogenetic study among its accessions could cover its slight cytogenetic data.In the present work, karyotype characteristics between 10 accessions of A. crassa were analysed by Aceto-Iron-hematoxilin staining method.

MATERIAL AND METHODS
The study was conducted at laboratory of cytogenetic of Agriculture Faculty of Guilan University, Iran.Nine accessions of A. crassa species obtained from gene bank of Seed and Plant Improvement Research Institute (SPII) of Iran and one accession collected by authors were used in this study (Table 1).Seeds were germinated on moist filter paper in petri dishes, kept at room temperature 20 -25 °C in the dark.Actively growing roots of about 1 -1.5 cm in length were excised, pretreated with a 0.002 M aqueous solution of 8hydroxyquinoline for 4 h at 4 °C, washed in distilled water for 10 -15 min and fixed in Lewitsky fixative at 4 °C For 30 -36 h.The fixative was prepared by mixing equal parts (in volume) of 1% chromic acid and 4% formaldehyde (10% formalin) just before using (Agayev, 2002).
The root tips were washed and hydrolyzed in 1 N NaOH for 7 min at 60 °C and stained with aceto-iron-hematoxylin 4% for 12 h at  25 °C.Stained roots were washed in distilled water for at least 10 min, then 1 -1.2 mm the root of tips were cut and macerated in cytase for 1.5 h.Each of the root tips was carefully transferred on a drop of 45% acetic acid on a slide for 3 -5 min, covered by cover slip and gently squashed.A number of 10 cells with well spread chromosomes were studied and photographed.
Chromosome measurements including long arm, short arm, chromosome lengths, arm ratio index and relative chromosome length were made with micro measure 3.3 software (Reeves, 2001).Chromosomes were designated according to Levan et al. (1964) and chromosomes were named as 1, 2, 3…13 and 14 in descending order of length.karyotype asymmetry was calculated according to Stebbins (1971).Statistical analysis performed by SPSS version 14 software.

RESULTS AND DISCUSSION
All the 10 accessions of A. crassa showed a tetraploid somatic chromosome number of 2n = 4x = 28 and this generally agree with the previously reported karyotype (Badaeva et al., 1998;2001).Size of long and short arms, relative lengths, L/S ratios and total chromosome length for each accessions are presented in Table 2. Means of karyotypic characters of fourteen mitotic chromosomes in 10 accessions are available in Table 3.These accessions had 13 m + 1 sm karyotype formula (Table 3).Karyotype for 10 accessions of A. crassa is presented in Figure 1.Arrangement of chromosomes in karyotype are based on mean of relative lengths of each chromosome in all accessions (Table 3).
Chromosomes number 3 and 9 are two chromosomes that consistently have satellite (Figure 1) and this is in agreement with previous studies (Chen-naveeraiah, 1960;Badaeva et al. 1998).Chromosome number 3 had a satellite in short arm, that is, in agreement with Badaeva et al. (1998) and number 9 had a satellite in the long arm, but Badaeva et al. (1998) reported that secondary constriction in this chromosome is located in the short arm.Some differences were observed among accesssions, for example, length of the individual chromosomes and arm ratio, which could be due to variety of reasons such as methods of measurement or use of different accessions.Results revealed that all chromosomes could be distinguishable by their morphology characteristics and this is in agreement with Badaeva et al. (2001).In these accessions, chromosome modifications such as variation in chromosome number or B chromosome was not seen.
All the accessions showed the symmetric karyo-type and were placed in 1A category of stebbines (1971) asymmetry categories.This shows that A. crassa acessions can be considered as relatively primitive acessions.However, some polymorphisms were observed among 10 accessions for karyotype characters.

Figure 1 .
Figure 1. of the 10 accessions of A. crassa.Arrow shows the satellite chromosome.

Table 1 .
List of studied accessions of A. crassa for karyotype analysis.

Table 2 .
The karyotypic characters of fourteen mitotic chromosomes in 10 accessions of Ae. crassa.

Table 3 .
The means of karyotypic characters of fourteen mitotic chromosomes in A. crasssa.