Cytological study and determination of ploidy levels in some hybrids of Kotra 10 cultivars of citrus plants

Exploration of ploid levels of citrus plants in the north of Iran which some of them have special charac­teristics, could be profitable in improvement of qualified and fertile citrus cultivars. In this case, six natural hybrids were selected from native citrus hybrids of kotar 10 in Mazandaran related to the center of citrus plants researches of country in Ramsar and were numbered from 7 to 12. These single hybrids have resulted from seeds of a hybrid named kotra 10. Which were studied after the rooting stage. Morpho­logical studies of these hybrids by use of squashing and staining have put them in the same class as Pseudo citrones. The number of chromosomes in all hybrids were determined to be 2n=2x=18. Morphological study of chromosomes in the Pseudo–citron, revealed that they were meta–centric chromosomes with few sub–meta–centric exceptions and relative length of chromosomes varied between 7% to 32% from big to small in all of hybrids. As a result, little differences were detected, in terms of size and morphology of chromosomes. The caryotypical characteristics, considering the homogeneity of the caryotype and the absence Variations among chromosomes in these caryotypes the hybrids will probably have been put in the early stages of evolution of phillogeny.