Karyotypic variation in some rapeseed (Brassica napus) cultivars using multivariate analysis

Karyologic studies were carried out on suitable metaphase cells of ten cultivars of Rapeseed (Brassica napus)، using squash technique، 0. 002 M 8-hydroxichinoline and 2% (w/v) aceto-carmin staining method. The chromosomal parameters measured were، short arm، long arm، chromosome volume، arm ratio، r-value، relative length and chromosome form percentage. Karyotype analysis showed that all cultivars were tetraploid (2n = 4x = 38). The resultant data were analyzed based on completely randomized design (CRD) with 5 replicates of cells. ANOVA indicated marked between-cultivars differences for most traits evaluated. On the basis of karyotypic formula، the cultivars had 4 types of chromosomes (M، m، sm، st)، categorizing in 8 different classes. Assessment of karyotype symmetry was carried out، using various parameters e. g. DRL، DI، TF%، S%، CV%، Stebbins and Romero-Zarco categories. The result of correlation coefficient showed that the short arm had the most correlation with form percentage، and chromosome volume had the least correlation with arm ratio. In cluster analysis based on UPGMA method، the distance was determined by eucldean distance dendrogram demonstrated 6 groups. The result of the principal components analysis showed that the first three components coverd 96. 1% of the data variation. According to the first two PCs، the cultivars were categorized into 6 groups.