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 me thod used to induce embryogenesis from Brassica napus microspores. Con tinuous culture at 25 degrees C results in pollen development. This st udy shows that colchicine alone, at the non-inductive temperature of 2 5 degrees C, can induce embryogenesis, thus demonstrating that heat sh ock is not required for embryogenic induction in B. napus cv. Topas. E mbryogenic frequencies of over 15% were obtained by culturing isolated microspores with 25 mu M colchicine for 42 h at 25 degrees C. The mic rospore developmental stages responsive to colchicine were unicellular vacuolate and late unicellular, somewhat earlier stages than the popu lation responsive to heat induction. Other groups have reported that h eat-shock proteins are essential to the induction of embryogenesis. Th e present study offers a method of embryogenic induction without the u se of heat which will allow discrimination between the factors associa ted with response to heat shock and those involved with changing cell development.