Studies On The Effect Of Exogenous1Ax1and1Dx5Overexpressions On Wheat Food-processing Quality By Creating RILs And ILs

Food-processing quality of wheat is largely controlled by high-molecular-weight glutenin subunits (HMW-GS). Previous studies have correlated stronger dough and better food-processing quality to the HMW-GS subunit lAxl and subunits pair1Dx5+1Dy10. Due to the importance of HMW-GS in determining dough properties, HMW-GS genes have been the targets in wheat molecular breeding to develop cultivars with improved dough quality, and most of research focused on1Ax1,1Dx5+1Dy10and1Dx5. While most successful transgenic wheat lines are produced using "model" wheat cultivars with high frequencies of transformation but with poor agronomic traits such as lower yield and weak adaptability. An alternative strategy is to introduce the transgenes from "model" transgenic wheat into elite wheat cultivars by combining particle bombardment mediated transformation with conventional cross and backcross. In this study, crosses and back crosses between transgenic wheat lines (B102-1-2/1(having transgene1Ax1), B72-8-llb and B73-6-1(having transgene Wx5)) and Chinese elite wheat varieties (Email2, Email8, Chuanmai107) were carried out. The pedigree selection was used to select the pure lines which contained exogenous1Ax1or1Dx5overexpression by SDS-PAGE screening method. Finally, we developed two sets of recombinant inbred lines (RILs) and five sets of introgression lines (ILs), including the lines having exogenous1Ax1or Wx5overexpression and the distrinct compositon of HMW-GS. The main results are as follows:(1) The resultant RILs and ILs showed robust and stable expression of1Ax1or Wx5, thus demonstrating the feasibility of improving food-processing quality by combining particle bombardment mediated transformation with conventional cross and backcross.(2) In all lines from RILs and ILs, exogenous1Ax1or1Dx5overexpression did not cause the silencing of endogenous HMW-GS nor did result in new-born subunits. While overexpression of exogenous1Ax1or Wx5caused the compensatory effects of endogenous gluten proteins, and this compensatory effects was more obvious in the lines containing1Dx5.(3) Overexpression of1Ax1in the cultivars Email2, Emai18and C107could improve the overall dough strength, but the effects in1Ax1-null background was more obvious than the background containing endogenous1Ax1;(4) A set of relatively complete ILs generated by the cross between C107and B102-1-2/1were developed and it is demonstrated that different quality depends on the different combination of HMW-GS, lAxl along with endogenous HMW-GS1Bx17+1By18and1Dx2+1Dy12gave better dough mixing properties than other HMW-GS combinations. When lAxl was overexpressed, subunit pairs1Bx17+lBy18contributed to the increased over-mixing tolerance of the dough, pairs1Bx7+1By9played an important role in the hydration during early mixing, expression of the1Dx2+1Dy12maintained an appropriate balance between x-type and y-type subunits and thereby improved dough quality.(5) Overexpression of1Dx5in the cultivars Emai12, Emai18, C107led to an excessive increase in gluten strength, showing an abnormal mixing behavior, thus resulted in poor food processing quality.(6) One line in ILs generated by the cross between Emai12and B73-6-1displayed abnormal phenomenon with the absence of a minor band (5’) which was accompanied with exogenous1Dx5due to the transformation, and the absence of this band resulted in the change of mixograms.(7) ILs generated by the cross between C107and B102-1-2/1exhibited agronomic performance similar to their recurrent parent C107, and significantly higher than the transgenic line, B102-1-2/1. Even some traits of ILs were superior to C107. The results along with the proven stability of exogenous1Ax1or1Dx5above demonstrated that the approach of improving food-processing quality by combining particle bombardment mediated transformation with conventional cross and backcross is valid. The germplasm resources we have developed are valuable materials for further breeding on wheat food-processing quality.