The Starch And Protein Accumulation Characteristics During The Development Of Proso Millet

Proso millet is one of the main crops in arid and semi-arid areas of northern China.The grains of proso millet are rich in nutrients including starch,protein,fat,dietary fiber,trace elements and vitamins.And it also can be used as the medical food.However,there are few studies on the mechanism of nutrients accumulation in the process of grain formation.Therefore,exploring the characteristics of grain development of different types of proso millet has great significance on improving the variety and developing resources.In this study,two waxy proso millet varieties(Longshu 21 and Jinshu 5)and two non-waxy proso millet varieties(Yumei 2 and Longmei 8)were selected as materials to study the dynamics of nutrients accumulation,the activities of starch synthesis related enzymes,the transportation of dry matter,the characteristic of grain-filling during the filling process of grains and the nutrient consumption during the process of seed germination.The main conclusions are as follows:(1)The accumulation of amylose,amylopectin and total starch showed a trend of S-type growth,and all the accumulation rate showed a single peak curve during the grain filling process.The amylose accumulation and accumulation rate of non-waxy millet varieties were significantly higher than those of waxy varieties,but there was no significant difference between amylopectin and total starch.The content of crude protein decreased and the content of gluten was the highest during the maturation of grains.The total protein content of the protein accounted for 19.36%~25.12%,non-protein nitrogen content more.The ratio of essential amino acids to total amino acids was 33.10%~52.93%,accounting for 48.53% ~ 78.22% of non-essential amino acids,which was rich in glutamic acid,proline and leucine.The lysine content of waxy varieties was higher than that of non-waxy varieties.The content of fat in the process of grain formation increased first and then decreased,and the change of water content showed a single peak curve,which increased first and then decreased,and the difference was not obvious between waxy varieties and non-waxy varieties.(2)The activity of ADPG-pyrophosphorylase(AGPP),soluble starch synthase(SSS),granule-bound starch synthase(GBSS)and starch branching enzyme(Q enzyme)all showed a single peak curve during the process of grain filling.The peak of the same enzyme activity appeared at the same time in different types of proso millet varieties,and the peak time between the enzymes was different.The AGPP activity and GBSS activity of non-waxy proso millet varieties were higher than those of waxy varieties in the early and middle stages of grain filling,while SSS activity and Q enzyme activity were lower than those of waxy varieties.The accumulation rate of total starch,amylose and amylopectin of waxy varieties was positively correlated with SSS activity and Q enzyme activity.In the non-waxy varieties,the amylose accumulation rate was positively correlated with the activity of AGPP,SSS and Q enzyme,the total starch accumulation rate was positively correlated with the activity of SSS and Q enzyme,the amylopectin accumulation rate was positively correlated with the activity of SSS.The SSS activity and Q enzyme activity play key roles in the process of starch accumulation of waxy proso millet varieties,while the accumulation of starch in the non-waxy proso millet varieties was mainly SSS.(3)The chlorophyll content of the top three leaves of different proso millet varieties were basically the same,which was gradually increased after reaching the peak at 14 days after anthesis and then decreased.And the content of chlorophyll in non-waxy varieties was higher than that of waxy varieties during whole filling stage.The top three stems had the highest contribution rate to grains,the top three leaves was the second,and the top three sheaths was the lowest.The contribution rate of the top three stems and the top three sheaths of non-waxy varieties were higher than those of waxy varieties,while the contribution rate of the top three leaves between the waxy varieties and the non-waxy varieties was not significantly different.The grain filling trend of different types of proso millet varieties was the same,and all of them were asynchronous grouting.From the flowering to the 28 d after flowering,the grain weight gain was the fastest.The grain filling curves of waxy millet varieties were below the non-waxy varieties and the highest grain filling rate of non-waxy proso millet and the average grain filling rate were higher than those of waxy varieties.Grain weight is determined by maximum grain filling rate,average grain filling rate,growth active period and actual grouting time.(4)The protein content was gradually increasing with the seed germination of different proso millet varieties.The content of albumin began to increase gradually from germination,and the content of albumin was higher than that of waxy varieties.While the changes of globulin,glutenin and gliadin were not obvious.With the germination of seeds,the starch content of different types of proso millet varieties reduced gradually,and the starch consumption of non-waxy varieties more than waxy varieties.With the seed germination,the activity of ?-amylase increased first and then decreased,and the peak of ?-amylase activity in waxy proso millet varieties was 1 d later than that of non-waxy varieties.?-amylase activity increased first and then decreased and increased again,and the activity of ?-amylase in waxy varieties was higher than that in non-waxy varieties during germination.The content of fat decreased gradually with the seed germination,while there were no significant changes between waxy varieties and non-waxy varieties.