Abstract: Tetraploids were induced successfully from in vitro Vitis.vinifera cv. Jingxiu and Red Globe by soaking shoot segments in colchicine solution and adding colchicine in the culture medium. Ploidy levels were determined by flow cytometry. The results showed that the soaked-treatment had increased efficiency of inducing tetraploids than one of adding in medium. Tetraploid plants were obtained from the shoot segments soaked in colchicine solution at concentrations of 2000 mg • L-1 or lower during 48 h or shorter time after two to four regenerations of micropropagation. However, when soaking was extended to 3 to 4 d at colchicines concentrations of 2000 mg • L-1 or when colchicine concentration was increased to 3000 mg • L-1 for 3 to 4 d, or 4000 mg • L-1 for 2 to 4 d, pure tetraploids were easily obtained during first micropropagation regeneration. The optimal conditions for inducing tetraploids were under soaking shoot segments for 3 to 4 d with colchicine at a concentration of 3000 mg · L-1. The rate of induction was 16.7-23.3%.

Key words: Grape, Colchicines, Polyploid, Analysis of ploidy