| Introducing C4 high photosynthetic efficiency system to C3 crops as wheat can improve the genetic basis of photosynthesis of C3 crops and which can greatly improved photosynthetic efficiency and then increase biological and grain yields of wheat. They are always important frontiers of science subject in crop breeding science. This research focuses that T2 and T3 generations of transgenic common wheat cultivars Zhoumai 19 with maize C4 type pepc gene was molecular screened by PCR. As experimental materials, positive transgenic plants were studied photosynthetic characteristics and group photosynthetic rate on the growth period under field condition, yield characters was surveyed after mature; transgenic plants in potted pattern were researched that the response curve of photosynthetic rate to light intensity and CO2 concentration at heading stage; PEPCase activity of transgenic wheat functional flag leaf was determined to study the correlation between photosynthetic rate and PEPCase. PEPCase function of transgenic plants was verified by DCDP which is specificity inhibitor of PEPCase. The researches provide theoretical basis and germplasm materials for selecting high photosynthetic efficiency wheat varieties breeding.The results were as follows: 1. Two higher positive genetically modified strains 1-45-2 and 1-47-3. respectively 66.5% and 60.5% positive rate, were molecular detected by PCR technology among 12 strains, 2094 plants of T2 generation transgenic wheat with maize C4 type pepc gene. They also are materials for following researches.2. The correlation between PEPCase activity and photosynthesis rate of five transgenic positive strains was studied. The result shows that great difference of PEPC enzyme activities among transgenic strains were greatly different, between 1.63μmol min-1 mg-1 and 4.90μmol min-1 mg-1; among them, PEPC enzyme activity of 1-45-2 transgenic strain was increased by 2.8 times and photosynthetic rate of 1-45-2 transgenic strain was improved by 34.4%, compared with the controls; positive correlation was between photosynthetic rate and PEPC enzyme activity; net photosynthetic rate of transgenic wheat processed with PEPCase specificity inhibitors DCDP and the control was not significantly difference. It proved that photosynthetic increase of transgenic wheat uwas really caused by PEPC enzymes activity.3. Diurnal variation of gas exchange parameters of transgenic wheat and Zhoumai 19 was determined at different growth stages (heading, anthesis,7th day after anthesis and 15th day after anthesis). The results show net photosynthetic rate of transgenic wheat was obviously increased at the four stages, including the heading stages, maximum Pn of two transgenic wheat strains,1-45-1 and 1-47-1, were 29.45μmol min-1 mg-1 and 28.20μmol min-1·mg-1.which was increased by 16.0% and 11.0% respectively; at 15th day after anthesis, maximum Pn of that were 25.63μmol min-1 mg-1 and 24.23μmol min-1 mg-1, which was increased by 23.3% and 13.7% respectively; Stomatal conductance (Gs) was increased significantly, the intercellular CO2 concentration (Cj) was reduced, transpiration rate (Tr) was increased, water useful efficiency (WUE) were significantly different, compared with the control. The statistical analysis found that increased Pn of transgenic wheat was negatively correlated with its Ci changes and the positive correlated with its Gs change.4. Chlorophyll fluorescence parameters of transgenic wheat strains and zhoumai 19 were measured at the morning and noon on 15th day after anthesis. The results showed that from 8:00 to 12:00, variation amplitude of Fv,Fm (the maximum photochemical efficiency), qP (the photochemical quenching), NPQ (non-photochemical quenching),φPSN (the actual photochemical efficiency of photosystemⅡ) of transgenic pepc gene wheat were less than control; compared 12:00 to 8:00, the Fv/Fm,φPSN and qP were all declined and which of transgenic wheat were obviously higher than the control; NPQ of transgenic wheat, compared 12:00 to 8:00,was appeared to rise. but was lower than that of the control. These results demonstrate that transgenic wheat has better resistance to stress at noon of high light and temperature.5. Response curves of net photosynthetic rate respectively to light intensity and CO2 concentration were measured based on T3 generation of transgenic pepc gene wheat and the control at the anthesis stage, the results showed that the ability of CO2 assimilation of transgenic wheat was enhanced; saturated photosynthetic rate of transgenic wheat was improved by 14.8%; comparing with the control. CO2 compensation point drops by 28.2% and saturated light intensity improves 6.9% from 1450μmol-m-2-s-1 to1550μmol·m-2·s-1, the carboxylase efficiency also improve by 28%. 6. Diurnal variation of canopy apparent photosynthesis (CAP) of T2 generation of transgenic pepc gene wheat strain 1-45-2 and Zhoumai 19 at the heading and anthesis stages were determined and mature yield traits were statistically analyzed. The results showed that value of CAP was bigger than the control Zhoumai 19. especially at 17th day after anthesis; the major yield characteristics, such as weight per stem, thousand grain weights, single spike weight and harvest index of transgenic wheat, were significantly higher than the control. The results described above indicated that the transgenic wheat expressing maize pepc gene showed better photosynthetic characteristics than untransformed plant and has the potential to increase wheat yield.These results indicated that transgenic wheat expressing maize pepc gene showed better photosynthetic characteristics than untransformed plant and has the potential of increasing wheat yield. |
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