Morphological and Cytological Studies of Colchicine-induced Polyploidy Lime (Citrus aurantifolia Swingle)

Abstract

Lime (Citrus aurantifolia) breeding was conducted by colchicine treatment to produce polyploidy lime. Healthy seeds were soaked in 0.4% colchicine for 6 hours. Polyploidy indicative morphologies, DNA content and chromosome number of putative polyploidy lime plants were verified. Measuring of DNA content by means of flow cytometric method showed 16% to treated plants contained two times of nuclear DNA content compared with the untreated control diploidy plants. Therefore indication of the tetraploidy lime plants were obtained. Consistency with the results of DNA content study, the chromosome number of tetraploidy plants and also the diploidy plants were 2n=4x=36 and 2n=2x=18, respectively when confirmed by squash technique and chromosome conting of root tip cells. Tetraploidy lime showed more significant thicker and broader leaves as well as larger guard cell size than diploid progenitor accompanied with significantly decrease of stomata and oil gland densities. Chromosome doubling of tetraploidy lime also increased lime fruit size, thickness of peel, seed size and seed number. Comparison with diploid, polyploidy lime fruit showed higher concentration of organic acid composition.