Cytogenetic Studies in Some Species of Medicago L. in Iran

IUFS Journal of Biology  IUFS J Biol 2014, 73(1): 21-30 Research Article Cytogenetic Studies in Some Species of Medicago L. in Iran Sara Sadeghian1*, Seyed Mohsen Hesamzadeh Hejazi 2 Research Center for Agriculture and Natural Resources of Fars Province Province, Iran Research Institute of Forests and Rangelands (Biotechnology Department), Tehran- Iran 1 2 Abstract A karyological study using the Image Analysis System was conducted of eight taxa of the genus Medicago L. namely M. radiata L., M. intertexta (L.) Mill. M. orbicularis (L.) Bart. , M. laciniata (L.) Mill., M. coronate (L.) bartal, M. rigidula (L.) All., M. polymorpha L.and M. scutellata (L.) Mill. used as forage plants from different geographic origins of Fars province from Iran. We found the two usual basic chromosome numbers in the genus, x=7 and x=8. In the group with x=7, two diploid (2n=14), one tetraploid (2n=28) species and in the group with x=8, five diploid (2n=16) species were found. Detailed karyotype analysis allows us to group the different species and to postulate relationships among them. Keywords: Chromosome, Fabaceae, karyology, Medicago, taxonomy *Corresponding Author:Sara Sadeghian (e-mail: ) (Received: 09.12.2013 Accepted: 21.07.2014) Introduction Medicago genus belongs to the tribe Trifolieae (Fabaceae, family). According to the IPNI reports the taxon includes about 396 annual and perennial species that have a widespread distribution from the Mediterranean to central Asia (Nixon 2006). This genus includes the widely cultivated major forage crop and weedy species M. sativa L. (alfalfa, lucerne) and the legume model species M. truncatula Gaertn. (Cannon et al. 2006). Taxonomically, Medicago along with Melilotus Mill. (sweet clovers) and Trigonella L. were included in the tribe Trigonellinae, first recognized by Schultz (1901), but as circumscribed this tribe was not accepted by most taxonomists. Instead, most authors recognized the tribe Trifolieae, which included these three genera and Trifolium L. (Rechinger 1984). Relationships within the genus are not yet sufficiently resolved, contributing to difficulty in understanding the evolution of a number of distinguishing characteristics such as aneuploidy and polyploidy, life history, structure of cotyledons, and number of seeds per fruit. Both polyploids and aneuploids are found within Medicago genus (Lesins and Lesins 1979). Polyploidy and chromosome rearrangement in the genus Medicago have resulted in the genetic isolation of genome groups. Diploid, tetraploid and hexaploid species all exist. Also, the union of two chromosomes in the genome and the loss of one centromere region has produced species with basic chromosome numbers of both x=8 and x=7. Some annual species have the base number x = 7 (Goldblatt 1981). The ploidy levels combined with differences in chromosome number have together provided a complete interbreeding barrier between members of this genus (Lesins et al. 1970). The first report about chromosomal number of Medicago was 2n=16 for M. disciformis and M. Arabica (Goldblatt 1975). It also recorded 2n=16 for M. marina and M. minima (Goldblatt 1978). The chromosome numbers of the M. rigidula rouges are different from 2n=14 (Goldblatt 1978) to 2n=16 (Goldblatt 1975). Different species of Medicago have 22 Sadeghian and Hesamzadeh Hejazi / IUFS Journal of Biology 2014, 73(1): 21-30 been recorded from diploid in M. orbicularis (2n=16) to tetraploid in M. scutellata (2n=32) (Goldblatt 1975). Medicago radiata or ray-podded medick is an annual plant species of the genus Medicago and belongs to the group of generic intermediates. It is found throughout the eastern Mediterranean and in Asia. Medicago intertexta or Calvary medick is an annual plant of the family Fabaceae. It is found primarily in the western Mediterranean basin area having spiny seed pods and leaves with dark spots. Medicago orbicularis is a winter annual plant with leafy stems, fimbriate stipules, oval non-hairy leaflets with toothed margins, orange-yellow flowers, and flat, coiled seed pods with no spines. It is found throughout the Mediterranean basin. It is also common along the European black sea coast. Common names include button clover and round-fruited medick. Medicago laciniata is a procumbent or ascending annual plant species of the genus Medicago. It is found primarily in the southern Mediterranean basin. Common names include cut-leaved medick and tattered medick. It grows in the Sinai, Egypt and is closely related to M. aschersoniana and may be hybridized with M. sauvagei (Singh and Lesins, unpublished). Medicago scutellata is an annual plant species of the genus Medicago. It is found throughout the Mediterranean basin. Common names include shield medick and snail medick. Deviating chromosome counts were given by Abdelguerfi and Guittonneau (1979) with 2n = 28 and Bauchan and Elgin (1984, cited in Goldblatt 1988: 109) with 2n = 30 chromosomes. Medicago coronata or crown medick is an annual plant species of the genus Medicago. It is found throughout the Mediterranean basin. Medicago rigidula is an annual plant currently interpreted as a Mediterranean species, indigenous to North Africa, Europe and Asia, and spontaneous in the new world and elsewhere (Small et al. 1990). The most intensive analysis of intraspecific variation of M. rigidula is that of Heyn in 1963 and 1984, who concluded her account by recording the great variability as well as the two recorded chromosome numbers (2n=14, 16). Medicago polymorpha is a Decumbent or ascending annual broadleaf plant species of the genus Medicago. Deviating chromosome counts were given (Fernandes et al. 1977; Fernandes and Queiros 1978; Labadie 1979, 1980) with 2n = 16 and (Dahlgren et al. 1971; Luque et al. 1988) with 2n=14. Common names include Bur clover and Bur medick. It is forage for livestock, but the fruit is prickly. It makes for a poor lawn in the late summer, when the leaves have yellowed and the fruit sets into the 7 mm seed heads that are covered with hooked prickles. Generally taxa will cross more readily when brought to the same ploidy level. Exceptions, however, are encountered where crossability at uneven levels is more successful. The 2n number alone, however, is of little use in determining thespecies relationship. For that purpose, karyotype studies may provide more information. Chromosome information is an important key for taxonomy, phylogeny, and evolution, genetic and breeding in Medicago plants. Here we present the report of the chromosome numbers, ploidy levels and comparison of karyotypic traits of some annual species of Medicago genus in Iran. Our results are useful for a better understanding of its taxonomy and breeding purposes such as inter and intraspecific hybridization and genetic variation induction. Materials and methods Plant material Complete specimens were collected in several field trips from various locations of the Fars Province (Iran) during their period of (...truncated)