CHROMOSOMAL LOCATION OF GENES-CONTROLLING SHORT-TERM AND LONG-TERM SOMATIC EMBRYOGENESIS IN WHEAT REVEALED BY IMMATURE EMBRYO CULTURE OF ANEUPLOID LINES

The expression of essential genes during somatic embryogenesis can be analysed by inducing aneuploid cells to undergo embryogenesis during i mmature embryo culture and then determining whether defects occur. Tri ticum aestivum disomic and aneuploid stocks, including 36 ditelosomics and 7 nullitetrasomic 'Chinese Spring' wheats, were compared for thei r ability to undergo somatic embryogenesis after 2 months of in vitro immature embryo culture. Their regeneration capacity was observed afte r 4 and 14 months of in vitro culture to determine which chromosome ar ms influence the process. The large range of variation found among the tested aneuploids suggested that genetic control of the somatic tissu e culture ability is polygenic. Our results indicate that genes affect ing somatic embryogenesis and regeneration are located in all of the h omoeologous chromosome groups. The lack of chromosome arms 1AL (DT 1AS ) and 3DL (DT 3DS) practically suppresses somatic embryogenesis, demon strating that major genes on wheat chromosome arms 1AL and 3DL control regeneration capacity. Results suggest that plants were mainly produc ed from somatic embryo development. Although the control of somatic em bryogenesis and regeneration is polygenic, the genes located on the lo ng arms of homoeologous group 3 chromosomes have a major effect. We al so have evidence of chromosome arms that determine the time required f or regeneration.