IN-VITRO INDUCTION OF TETRAPLOIDY IN MULBERRY (MORUS-ALBA L.)

A high frequency of tetraploidy was induced in mulbeny (Morus alba L.) through apical bud treatment under ia vitro conditions. Apical buds f rom in vitro-grown plants were treated with three different concentrat ions (0.05, 0.1 and 0.2%) of colchicine in MS medium for 24 h. Tetrapl oidy at a frequency of 39.4+/-4.8% was obtained using 0.1% colchicine, whereas the frequency of tetraploidy was significantly reduced to 16. 7+/-2.3% when 0.2% colchicine was used. Morphological, histological an d cytological evidence indicated a phenotypic and genomic similarity o f in vitro- with ex vitro-induced tetraploids. Rooting of tetraploids was on basal medium containing 2.6 mu M NAA. The recovery of tetraploi ds was 80.8% more efficient using the in vitro method instead of the e x vitro method. The use of the same colchicine medium for up to 4 week s with additional explants was found to be equally effective for the i nduction of tetraploidy.