EMA based chromosome analysis in Bixa orellana L. and Limonia acidissima L

Abstract

Determination of chromosome number and their analysis particularly in vast number of economically important medicinal tree species are far from complete. Chromosome analysis provides information on chromosomal behaviour and identifies the plant with a particular karyotype formula which is the basis of genome analysis in a particular species. The present communication considered two medicinally important almost unattended Indian tree species, Bixa orellana L. and Limonia acidissima L., for chromosomal analysis using an improved cytogenetic protocol of Enzymatic Maceration and Air drying (EMA) method followed by Giemsa staining [5]. Chromosome analysis of Bixa orellana reveals to contain 2n = 14 chromosomes with karyotype formula represented by 4 M + 10 m. Chromosomes are relatively smaller in size (1.30–3.40 μm) and total chromatin length varies from 24 to 30 μm among the observed metaphase plates. Karyotype is bimodal due to the presence of a visibly long pair of chromosomes which are almost two times longer than all other pairs. Limonia acidissima L. confirms to contain 2n = 18 chromosomes and has a karyotype formula of 16 m + 2 m.t. Chromosomes are relatively smaller in size (1.53–2.83 μm) and total chromatin length varies from 32 to 43.5 μm among observed metaphase plates. Both the species show symmetrical karyotype with predominance of chromosomes showing median or nearly median primary constrictions. These chromosomal data will be useful in genome analysis of these economically important plant species for future improvement programmes.