Evaluation of genetic variation among three species of Allium on the basis of karyomorphology and SDS-PAGE profiling

Abstract

Determining the base number, ploidy level and type of ploidy are important aspects in the cytogenetic study of a species. Genetic variation among the three species of the genus Allium (A. cepa, A. sativum and A. hookeri) has been carried out on the bases of chromosomal karyotype and protein banding patterns on SDS-PAGE. Protein profiling was prepared from the observed bands on SDS-PAGE after electrophoresis and staining with coomassie brilliant blue. Shoot protein was extracted in phosphate buffer (pH 7.5) and run on gel for 3 hours at 20 mA constant current. Band numbers were varies from 31 to 39 in different position on the gel according to their Rf value. Bands were scored as binary data and computed in MVSP software for dendrogram analysis to examine their genetic relationship using Jaccard's coefficient. Three species were grouped into three distinct clusters in the dendrogram. Species cepa and sativum was grouped at the similarity coefficient value of 0.53 and species hookeri was placed in separate group at coefficient level of 0.40. Genetic variation was also examined on the basis of PCA analysis. The number of chromosome were found to be present 16 in Allium cepa,16 in Allium sativum, and 22 in Allium hookeri. The shortest chromosome in Allium cepa was 8.75(μm) and the longest one was 23.12(μm) with the ratio of shortest/longest chromosome of 0.37, the mean chromosome length of 15.23(μm) and a mean centromeric index of 0.16%. The shortest chromosome in Allium sativum was 10.62(μm) and the longest one was 30.0 (μm) with the ratio of shortest/longest chromosome of 0.35, the mean chromosome length of 17.41(μm) and a mean centromeric index of 0.60%. The shortest chromosome in Allium hookeri was 5.62 (μm) with the ratio of shortest/longest chromosome of 0.21, the mean chromosome length of 16.58(μm) and the mean centromeric index of 0.46%. Allium hookeri is considered to be much more advanced than the rest of the species (Allium sativum, and Allium cepa) because karyotype of the A. hookeri was ranges from submediam to telocentric chromosome, which is evolutionarily advance characters.