Construction Of Embryo-based Regeneration And Genetic Transformation In Common Wheat

Plant regeneration system and genetic transformation are important for molecularimprovement on major crops. In this study, mature and immature embryo-based regenerationwas developed in one or several important wheat cultivars; stable or transient genetictransfroamtion was made in wheat cultivar “Bobwhite”, which lays important foundation forwheat improvement.（1）In this study, five“Jimai”wheat cultivars/genotypes, including Jinan17, Jimai19,Jimai20, Jimai21and Jimai22, were used to test the effects of phytohormones2,4-D, ZTand KT on mature embryo-based callus induction, differentiation and regeneration.Bobwhite, which has been widely used in transformation studies, was used here as a control.The results show, compared with Bobwhite,“Jimai” wheat cultivars have higherpercentages of callus induction, and among different cultivars, there are significantdifferences beacuse of genotype effect. At the same concentration of2,4-D in the callusinduction (CI) medium, genotypes had significant effects on the callus differentiation andregeneration. According to the percentages of regeneration,“Jimai” wheat cultivars havelower performances than that of Bobwhite. Therefore, improving the regeneration rate ofdifferentiated calluses is the key step to construct wheat mature embryo based regenerationsystem. When the genotype was same, different concentrations of2,4-D in the CI mediumshowed significant influence on callus induction, differentiation and regeneration. With thesupplement of4mg/L2,4-D in the CI medium, all tested genotypes except Jimai20regenerated, and the regeneration rate of Jimai22is10.33%, close to that of Bobwhite.This study provides a basis for developing mature embryo-based regeneration system in“Jimai” wheat cultivars.（2）Using gene gun bombardment, stable transformation was developed on wheat immatureembryos of “Bobwhite”. Under the BAR–conferred herbicide screening, the systemassociated with a2%transformation efficiency.（3）Using the established transformation protocols, four target genes including Yr10, Yr18,Yr36, and FT, were introduced to “Bobwhite”. FT gene controls the flowering time.Downregulation of the FT by RNAi construct delays the flowering time dramatically.（4）The transformation efficiency was significantly affected by various factors such asvector size, linear or circular status of target genes. Large vectors associated with lowertransformation efficiency; while circular plasmid was easier to be transformed than linear plasmid. For example, linear and circular plasmids carrying the BAR gene corresponded to0.39%and2.02%transformation efficiency, respectively.