Cytological comparison of two cultivars 7 Range Mgmt. & Agroforestry 31 (1) : 7-10, 2010 ISSN 0971-2070 Cytological comparison of two cultivars of Egyptian clover ( Trifolium alexandrinum L) Magda I. Soliman 1 , E. M. Zayed *2 and G. A. Ramadan 2 Department of Botany, Faculty of Science, Mansoura University, Mansoura, Egypt. *Corresponding author e-mail : ehabzayed31@hotmail.com Received : 20 th August, 2009 Accepted : 25 th April, 2010 Abstract Cytological studies including chromosome number and karyotype analysis have been carried out on two cultivars ‘Helaly’ and ‘Fahl’ in Egyptian clover (Trifolium alexandrinum L.). The somatic chromosome counts for two cultivars were 2n = 16. Karyotype analysis showed differences in chromosome morphology. Chromosomes nsm (+) were observed in cultivar Helaly. The karyotype formula for Helaly was 2 nsm (+) + 2 nsm (-) + 12 nm. For Fahl, 6 nsm (-) + 10 nm were recorded. Helaly had highest A1 and A2 where Fahl had highest TF %, S%, Syi index and Rec index. Karyotype analysis revealed that cultivar Helaly is advanced one whereas cultivar Fahl is primitive. Chromosomal abnormalities were observed at mitotic division, which was higher in cultivar Fahl. Keywords : Chromosomal abnormalities, Chromosome number, Fahl, Fodder, Helaly, Karyotype analysis, Trifolium alexandrinum Introduction Egyptian clover (Trifolium alexandrinum) is one of the most important legumes of the Middle East and the Mediterranean because of its multicut nature. However, only single cut is possible from its ecotype Fahl. Cytological characters, including chromosome number and karyotype analysis have been considered important tool for taxonomic and evolutionary relationships (Moore, 1968). The number, size and shape of chromosomes were used to characterize the karyotype and define the taxonomic differences. The purpose of this study was to investigate chromosome number of two cultivars Helaly and Fahl, construct karyotypes and to reveal the types of mitotic irregularities if present and their frequencies. Materials and Methods Viable seeds of the two cultivars, Helaly and Fahl were obtained from Forage Crops Research Department (FCRD), Field Crops Research Department (FCRI), Agricultural Research Center (ARC), Giza, Egypt. Seeds were germinated and actively growing root tips were pretreated for 2-4 h in 0.002 M 8- hydroxyquinoline, fixed in 3:1 (absolute ethanol : acetic acid), hydrolyzed for 5 min in 1 N HCl at 60 0 C and stained in aceto-orcein according to Lacour (1941); Chattopadhyay and Sharma (1988). Well spread five metaphase plates were selected and photographed. Karyograms were drawn and lengths of long arm (L) and short arm (S) were measured for karyotype analysis. Karyotype analysis was carried out using “Micro Measure” Computer Program (Reeves, 2001). Mean chromosome length (MCL) in μ, the total chromosome volume (TCV) and the total chromosome length (TCL) were determined. To estimate karyotype asymmetry, two numerical parameters, A1 (intra-chromosomal asymmetry index) and A2 (inter-chromosomal asymmetry index) were used according to Zarco (1986). Symmetry percent (S%), Rec index (resemblance between chromosomes), Syi index (the symmetric indices) and the total form percent (TF %) i.e., the average degree of symmetry over the whole karyotype were calculated according to Huziwara (1962). Results and Discussion The two cultivars of Trifolium alexandrinum L. in the study were found to be diploid (2n= 16) (Plate 1) which is in confirmation with previous reports of the same genus (Bir and Kumari, 1979). There were substantial differences in karyotype of the two cultivars. The dissimilarity was found in the morphology of chromosomes and also in the mean chromosome length (MCL), total chromosome length (TCL) and total chromosome volume (TCV). The values of MCL, TCL and TCV were higher in cultivar Helaly than in Fahl (Table 3). The first chromosome in Helaly was longer than that of its counterpart in Fahl (Table 1) whereas eighth pair was shorter in Fahl than that in Helaly (Table 2). These differences might be due to chromosome deletions or due to different levels of condensation and differential contraction of chromosomes as suggested by El-Nahas 2. Forage Crops Research Department, Field Crops research Institute, Agriculture Research Center, Giza- 12619, Egypt.