Assessment of various stresses and carbohydrates for their effect on the induction of embryogenesis in isolated wheat microspores

Isolated microspores of flowering plants can undergo embryogenesis when cultured in vitro under appropriate conditions. This process is triggered by various stresses including cold, heat and starvation. We have studied the effects of these stresses on the induction of embryogenesis in wheal microspores isolated from freshly cut or cold pretreated tillers. We show that the stress can be applied directly to microspore cultures, and efficient induction of embryogenesis can be obtained from microspores using a variety of stresses, namely cold (4 degrees C), heat (33 degrees C) and carbohydrate/nitrogen starvation. Cold pretreatment of tillers was able to replace stresses applied to microspores. For the first time we report on embryo formation in true ab initio wheat microspore cultures, not requiring any pretreatment of anthers or tillers prior to culture, in a maltose-containing medium. The effect of maltose on the induction of wheat microspore embryogenesis was specific and can possibly be attributed to its slow hydrolysis by plant cells, exerting starvation conditions early in culture and stable osmolarity of the medium later on. A comparison of three protocols for the induction of wheal microspore embryogenesis and plant regeneration has revealed no significant difference in plant yield, but the ploidy of the plants obtained was affected. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.