NUCLEOLAR CHROMOSOME VARIATION AND EVOLUTION IN THE GENUS VICIA

The nucleolar chromosomes in the genus Vicia usually comprise one or r arely two pairs of the complement in the diploid (2n = 10, 12, 14; x = 5, 6, 7) taxa. Barring V. anatolica nucleolar chromosomes in compleme nts of various species have one secondary constriction and one satelli te each. In V. anatolica (2n = 2x = 10) one of the two nucleolar chrom osome pairs contained two secondary constrictions and two satellites. The nucleolar chromosomes in Vicia species show substantial variation, in satellite size from very minute to highly conspicuous, in the loca tion of primary and secondary constrictions from terminal to mid regio n, and in the size of mid arm from very small to about 90 per cent of the total chromosome size. On the basis of proportionate size of the t hree stainable components, the nucleolar chromosomes in Vicia species have been classified into eighteen distinct types. The comparative mor phology of the nucleolar chromosomes shows that interchanges including Robertsonian fusion, deletion and/or inversion have mainly contribute d to their divergence and evolution. Overall, the nucleolar chromosome variation showed a good correlation with the taxonomic classification . The present results provide probably the first example of an astonis hing array of diversity in the form and shape of nucleolar chromosomes within a genus.