Karyological Evaluation of Five Hybrid Cultivars of Sugarcane (Saccharum officinarum L.)

Classical cytological studies were carried out to give karyological information about five hybrid cultivars of sugarcane. Root tips pretreated with saturated α-bromonaphthalene solution for 8 h at 4 °C. The roots were fixed in 1:1 chromic acid 1%: formaldehyde 10% for 48 h, followed by hydrolysis in 1N NaOH for 15 min at 60 °C. After enzymatic digestion of Hematoxylin-stained roots, each root tip was squashed in a drop of 45% acetic acid. Karyotype analysis showed that chromosome size varied from 0.571 μm to 5.076 μm with predominance of m chromosome types so that more than 50 paired chromosomes were m type in each cultivar. Multivariate tests of significance and ANOVA showed that, except for TF%, the means of Symmetry Index, Dispersion Index, Difference of Range of Relative Length, Coefficient of Variation, and Haploid Set Length were significantly different among cultivars. The karyotypes were similar with respect to TF%-based symmetry and centromere position of more than 90% of the chromosome pairs. These results showed apparently, that the evolution of karyotype in S. officinarum has mainly involved chromosome number and polyploidy rather than chromosomal changes and karyotype asymmetry