Abstract
A technique for the in vitro colchicine treatment of microspore‐derived haploids of rape (Brassica napus L.) is presented. This allows effective and time‐saving chromosome doubling. The most effective method consists of an application of 50 mg/1 colchicine in a liquid B5 medium to the rooted micro‐spore‐derived plantlets for 4–8 days. By this treatment more than 50 % of the plants developed at least diploid sectors. A change of medium after some days may even increase this diploidization rate.