Differences In Yield And Quality Of Different Millet Varieties And Transcript Analysis At Lipid Accumulation Stage

Foxtail millet(Setaria itclica(L.)Beauv.)is a kind of important grain and economic crops in the Yellow River basin in northern China,with a long history of cultivation.The grains rich in fat,protein,amino acids,unsaturated fatty acids,and other essential nutrients for human.Millet has become a kind of popular health foods.With the improvement of mechanization in agriculture and the promotion of advanced agricultural technology,the planting area of foxtail millet rebounded.And it is a key way to realize millet light and simple and efficient cultivation through mechanization and popularization of herbicide resistant varieties.In addition,the deshelled grains contain fat which is easy of oxidative rancidity,affecting commodity quality.Therefore,the selection and promotion of foxtail millet varieties with different fat levels is also one of the key problems to be solved urgently according to the market demand.Hence,it is imperative to study the accumulation characteristics of fat,protein,starch and other nutrients in grains of herbicide resistant foxtail millet varieties during filling process,analyze the accumulation characteristics of nutrient components in grains from different ear axis position,and dissect the characteristics of fat accumulation transcripts,which lays the foundation for breeding and high quality cultivation of herbicide resistant foxtail millet varieties.Four varieties of foxtail millet with significant differences in fat and other traits were selected from 59 varieties on the basis of comprehensive consideration of agronomic characteristics from 2017 to 2018,two of which were herbicide resistant varieties(JG35 and JG39),and the others were control varieties(3741 and 8852).Dry matter transport and yield components of foxtail millet were studied.The dynamic characteristics of fat,fatty acid,protein,amino acid,starch and yellow pigment accumulation during filling process were analyzed.And the fat accumulation transcripts of herbicide resistant millet varieties were dissected.The main points and the results are the following.(1)During filling process of herbicides resistant millet varieties,the change of relative content of chlorophyll in the top-three leaves showed similar regularity of the maximum was at 14-d after anthesis and then decreased gradually.The dry matter transport of different varieties of foxtail millet during grain filling process indicated that the average contribution rates of top-three leaves and top-three sheaths were higher than that of top-three stems,and there was a significant positive correlation between yield and stem diameter,panicle length and 1000-grain weight.Therefore,the panicle development of millet can be promoted through the rational management of fertilizer and water,and the yield of foxtail millet can be improved.(2)The trend of nutrition accumulation of herbicide-resistant millet varieties was similar to that of control varieties during grain filling process.The content of fat increased first and then decreased,while the content of protein was decreasing.And the content of starch,amylose and amylopectin increased,while the content of yellow pigment increased first and then decreased.In addition,the grains were rich in unsaturated fatty acids,where linoleic acid(C18:2cis)was the most,followed by oleic acid(C18:1cis).Besides,there were various species of amino acid in grains,because E/T and E/N were 34.10%-35.72% and51.74%-55.57%,respectively.Furthermore,the content of fat,starch and yellow pigment was the most in the middle spikelet at the early stage of filling process,while the content of protein during the whole stage of grain filling process was in the following order: middle spikelet > upper spikelet > lower spikelet.(3)A total of 163.34 Gb Clean Data were obtained by sequencing analysis of transcripts,and 2,201 new genes were discovered based on the comparison results.1,432 genes were annotated and the structures of 6,452 genes were optimized.At the different stages of grain filling process of JG35,1,920 genes were up-regulated and 1,297 genes were down-regulated compared with JG39.And 47 genes in the annotated transcripts were related to fatty acid synthesis by work annotation analysis of pathway gene.Additionally,36 genes were associated with fatty acid chain extension and 43 genes were associated with the synthesis of unsaturated fatty acids.