Study On Nitrogen Response Mechanism Of Different Genotypes Of Sorghum In Alpine Region

With the advancement of breeding methods,sorghum varieties in Heilongjiang province have transitioned from medium-high stalk and sparse planting to short-stalked dense planting mechanized production.Nitrogen is an essential nutrient element for sorghum growth and development,previous studies mainly used medium-high stalk and sparse planting as the research background,there are few systematic studies on the mechanism of nitrogen metabolism and response to low nitrogen,and the research report is still blank on alpine region.In this article,the mechanism of carbon and nitrogen metabolism of density-tolerant sorghum was studied,and the basic law and difference mechanism of physiological response of different genotypes of sorghum were clarified.At the same time,the biological mechanism of nitrogen regulation on density-tolerant sorghum was discussed through transcriptome analysis,and nitrogen absorption and utilization and tolerance were predicted and analyzed metabolic pathways and related genes in response to low nitrogen.This study has an important significance to understand the nitrogen effect and metabolism mechanism of sorghum in alpine region,lay a foundation for the general mechanism of molecular assisted breeding of low nitrogen tolerant sorghum,and provide a theoretical basis for the formulation of high-efficiency cultivation technology in alpine region.The main results were as follows:1.Through the comparison of field low nitrogen tolerance index and the selection of NR,GS activity and chlorophyll content in seedling stage,Keza15 was selected as low nitrogen tolerant sorghum variety,and Suiza7 as nitrogen sensitive sorghum variety.During the evaluation of two different sorghum genotypes,it was found that chlorophyll b was sensitive to low nitrogen stress.2.The dry matter accumulation from loose powder to grain filling stage played a decisive role in the yield of the two sorghum varieties,and the effect trend of nitrogen on dry matter accumulation and distribution proportion was consistent.With the increase of nitrogen,the yield of nitrogen sensitive varieties increased more than that of low nitrogen tolerant varieties.Protein content increased with the increase of nitrogen application,while the content of starch,fat and tannin increased at first and then decreased with the increase of nitrogen application.N200(pure N 200kg/hm~2)treatment can ensure higher yield and better brewing quality,which is the best nitrogen application amount.3.The activity of NR,GS,GOGAT and GLDH in leaves increased with the increase of nitrogen,and the correlation coefficient between nitrogen and NR activity and GS activity was higher.Low nitrogen treatment could significantly reduce the PRO content of sorghum,the response of PRO activity of nitrogen sensitive varieties to nitrogen was higher than that of low nitrogen tolerant varieties,and MDA activity was lower than that of low nitrogen tolerant varieties.The activity of SOD and POD decreased significantly under low nitrogen treatment,and the response of nitrogen sensitive varieties to nitrogen was more significant than that of low nitrogen tolerant varieties.4.The starch accumulation of nitrogen sensitive varieties increased more than that of low nitrogen tolerant varieties,the 14-35 days after powdering is the key period of starch accumulation.The correlation coefficient between SS,SSS,SBE,GBSS,ADPGpase,UDPGpase and amylopectin content was the highest and extremely significant at 14 days after powdering,and the correlation coefficient with amylose was the highest and extremely significant at 28 days after powdering,the correlation coefficient between total starch content and grain number per ear,1000 grain weight and yield was significant.Compared with low nitrogen tolerant varieties,high nitrogen was beneficial to the improvement of SBE activity,GBSS activity and UGP activity of nitrogen sensitive sorghum varieties.5.Transcriptome analysis showed that the differential gene expression in the chlorophyll of Suiza7 was more abundant than that of Keza15,and the transcriptional code of nitrate transporter NRT2.4,NRT3.1 and NRT4.5 were more abundant in the low nitrogen tolerant varieties than that of the nitrogen sensitive varieties.6.Photosynthetic system and extracellular region play a key role in nitrogen tolerance of sorghum.Secondary metabolite biosynthesis,porphyrin and chlorophyll metabolism,photosynthetic antenna protein and so on are related to nitrogen absorption and metabolism.The common low nitrogen response genes of the two sorghum varieties were mainly concentrated in the classification of nitrogen metabolism and glutathione metabolism.In this study,MYB transcription factors were found to play an important role in the process of low nitrogen stress in sorghum.It was also found that ERF,b HLH,WRKY,NF-Y transcription factors were involved in the response process of low nitrogen tolerant sorghum.