ارتباط ميان سطح پلوييدي و تعداد كلروپلاست هاي سلول هاي محافظ روزنه در سرده يونجه

Relationship Between the Ploidy Level and Chloroplast Number in Stomata) Guard Cells of Medicago sp.

Determination of ploidy level is requird for studying interspecific relationship, genetics of transgenic plants and developing interspecific hybrids in breeding programs. Genus Medicago is the most important forage crop of Fabaceae family. There are almost 85 annual and perennial species under this genus. Species of this genus have small chromosomes with different ploidy levels, requiring extensive ploidy analysis in its breeding program. Therefore, an efficient technique is needed for determination of the ploidy level. The relationship between ploidal level and the number of chloroplasts in stomatal guard cells was studied in order to examine the possibility of using cloroplast count as an alternative to chromosome count. Three randomly selected middle leaves of greenhouse grown plants were used for chloroplast counting in twenty pairs of stomatal guard cells per each leaf. Chromosome numbers were also determined in root tip squashes of studied plants. The ploidy level was highly correlated with the number of chloroplast in stomatal guard cells of lower surface of the leaf. Number of chloroplasts in tetraploid species M saliva L., M. scutellat (L.) Mill. Gard. and M. rugosa Desr. was approximately twice as many as the number of chloroplasts in diploid species M coronata (L.) Bartalini, M. radiate L., M rigidula (L.) All., M. polymorpha L., M constricta Durieu., M. noeana Boiss., M. minima (L.) Bartalini., M. truncatula Gaetn., M littoralis Rhode., M orbicularis (L.) Bartalini., M. laciniata (L.) Mill. Gard., M. arabica (L.) Huds., M. ciliaris (L.) Krocker. and M. lupulina (L.). Our results suggest that this method can successfully be used for determination of ploidy level in Medicago species.