| To explain the profound mechanism, a high-starch maize variety and a common maize variety and their inbred lines used as experimental materials, the dynamic accumulation of grain starch (total starch, amylose, amylopectin) and the activity changes of key enzymes involved in starch synthesis during grain filling period were compared, besides, the activity changes of key enzymes, the correlation of starch accumulation among the two different varieties and their inbred lines and heterosis were analyzed. The main results showed as follows:1 The changes of the accumulation content of starch of the high-starch variety and common maize variety and their inbred lines at grain filling stage all increased in'S'curve fashion. As for the content of total starch, the high-starch maize variety (zhengdan 18) was significantly higher than the common one; and the high-starch maize inbred line (zheng 29) in starch content indicated constant higher, compared with the common inbred line (zheng 58). To the two different starch content maize varieties, the difference in starch content was apparently smaller than that in amylopectin content; while the distinction in the amylose and amylopectin content among high-starch maize varieties was more significant than that among common ones. In total starch content, Zheng 29 as the parent of zhengdan 18 was obviously higher than zheng 258,the parent of zhengdan 958.On the basis of the data, it could be suggested that the discrepancy in total starch content of the 4 types was mainly because of the different amylopectin content in kernals.2 The heterosis values of over mid-parent, over high-parent and over low- parent were positive. To the high-starch maize variety, zhengdan 18,these values were 11.24, 9.89, and 12.66, respectively. In comparison with the common maize variety, it performed higher heterosis. 3 The high-starch maize variety, zhengdan 18 and its parent zheng 29 with higher sucrose from the fifth day to the thirtieth day after anthesis, it indicated the sufficient sucrose could meet the requirements of the starch synthesis.In the grain growth stage, and changes in activities of sucrose synthase(SS), adenosine diphosphorate glucose Pyrphorylase(ADPGPPase), uridine triphophate glucose pyrphorylase(UDPGPPase), soluble starch synthase(SSS), Granule-bound starch synthase(GBSS), and starch branching enzyme of four types appeared single-peak curves.To Zhengdan 18, the high-starch maize variety and its parent zheng 29, the activities of SS, ADPGPPase and GBSS were higher than zhengdan 958 and zheng 58.The activity of SS was of no significance correlated with the starch accumulation; however, the activities of ADPGase, SSS and GBSS in high-starch maize variety and its parent have a significantly positive correlation to total starch, as for the common maize variety and its parent, the ADPGPPase, SSS and SBE's activities were significantly positively related with total starch accumulation. The results indicated that the starch accumulation of high-starch maize was mainly regulated by the activities of ADPGPPase, SSS and GBSS; but for the common maize variety, ADPGPPase, SSS and SBE were the key enzymes to the synthesis of maize starch. |
