Induction of embryogenesis with colchicine instead of heat in microspores of Brassica napus L cv Topas

Prior to this report, heat treatment (32.5 degrees C, 24 h) was the method used to induce embryogenesis from Brassica napus microspores. Continuous culture at 25 degrees C results in pollen development. This study shows that colchicine alone, at the non-inductive temperature of 25 degrees C, can induce embryogenesis, thus demonstrating that heat shock is not required for embryogenic induction in B. napus cv. Topas. Embryogenic frequencies of over 15% were obtained by culturing isolated microspores with 25 mu M colchicine for 42 h at 25 degrees C. The microspore developmental stages responsive to colchicine were unicellular vacuolate and late unicellular, somewhat earlier stages than the population responsive to heat induction. Other groups have reported that heat-shock proteins are essential to the induction of embryogenesis. The present study offers a method of embryogenic induction without the use of heat which will allow discrimination between the factors associated with response to heat shock and those involved with changing cell development.