Cytology of Different Species of Gardenia with Special Reference to the Value of Karyotypes as an Aid to Identification

Abstract

1. Cytological studies on six different species and varieties of the genus Gardenia have been performed. All the individuals have been found to be characterized by 2n=22 chromosomes. The species are:-
i) Gardenia jasminoides Ellis
ii) G. jasminoides Ellis var. stanleyana
iii) G. jasminoides Ellis var. fortuniana
iv) G. tubifera wall.
v) G. lucida Roxb.
vi) G. kirkii
2. Detailed karyotype analysis of all these species have been carried out and each species has been shown to have a distinct karyotype of its own. This shows that changes in chromosome morphology have been an associated feature of their evolution.
3. Chromosomes are mostly medium in size with generally median to submedian primary constrictions. Number of chromosomes with secondary constrictions have been found to vary from four to ten. In G. jasminoides, a pair of chromosomes with supernumerary constrictions has also been recorded.
4. Nuclei with altered chromosome complements have been noted in the tissue of the same species and their role in evolution has been discussed. It has been suggested that these altered chromosome complements can give rise to daughter shoots with different genomic constitution maintained in otherwise normal numbers.
5. Numerical variations of chromosome number in the somatic tissue have also been detected. In absence of any species with different chromosome number, numerical variations seem to play no important role in speciation of this genus.