Comparison Of Gene Expression Related To Panicle Type In Rice Varieties And Its Response To Nitrogen Fertilizer And Density

Panicle traits are important components of rice plant architecture and yield,including panicle size,shape,and grain density.The rice panicle is a cone-shape panicle,which is composed of primary branches,secondary branches,spikelet branches and spikelets.The number of spikelets during the formation of young panicle differentiation is one of the key factors to determine panicle shape and yield.Different genotypes of rice varieties showed great differences in panicle traits under the same environment and under different environmental conditions.Nitrogen fertilizer and seedling density in holes are important nutrient elements and cultivation measures that affect the growth and development of rice,and play an important regulatory role in rice traits and gene expression.To study the dynamic variation of related compounds,enzyme activities and gene expression related to young panicle differentiation during panicle formation and panicle traits in different genotypes of rice,as well as their response to environmental regulation is important to clarify the molecular regulatory mechanism of panicle development,to breed the super-high-yield rice varieties and to establish super-high-yield cultivation techniques theoretically and practically.In this study,different genotypes of japonica rice varieties(lines)GWS 15,Songjing 9,Dongnong 7366,Longdao 27,GWS 14,and Longdao 5 were selected to systematically compare and analyze young panicle differentiation,young panicle differentiation-related traits and enzyme activities,cytokinin,related gene transcription and expression,panicle traits and their responses to different nitrogen fertilizers and densities in holes and their changes,to clarify the molecular regulatory mechanism of panicle development and super high-yield rice breeding and cultivation theoretically.The research results are as follows:(1)There are significant genetic differences in panicle traits between different genotypes.According to the total number of grains per panicle,the 6 tested varieties can be divided into multi-grain varieties Songjing 9 and GWS 15,and more grain varieties Dongnong 7366 and Longdao 27,fewer-grain varieties GWS 14 and Longdao 5;the order of the number of secondary branches per panicle is Dongnong 7366>GWS 15>Songjing 9>Longdao 27>GWS 14> Longdao 5;the order of the grain number per primary branch is Longdao 5>Longdao 27>GWS 14>Songjing9>GWS 15>Dongnong 7366;the order of the grain number per secondary branch is GWS15>Songjing 9>Dongnong 7366>Longdao 27>GWS 14>Longdao 5.(2)Under the exogenous nitrogen treatments,the largest increase in the total number of grains per panicle,the number of secondary branches per panicle,and the grain number of secondary branches per panicle is GWS 14,the smallest is GWS 15,and the largest increase in panicle length per panicle is GWS 14,the smallest is the variety with more grain type Longdao 27.The largest increase in the number of primary branches per panicle and the grain number of primary branches per panicle is Longdao 27,GWS 15.With the increasing of the density in the hole,there are great differences of the same trait among different grain-setting varieties.With regard to the total grain number per panicle,the length of each panicle,the number of secondary branches per panicle,and the grain number of secondary branches per panicle,the largest decrease is GWS 15,the smallest is GWS 14,and the largest decrease of the number of primary branches per panicle is GWS 15,the smallest is Longdao 27,the largest decrease in the grain number of primary branches per panicle is GWS 14,and the smallest is Longdao 27.(3)During the formation of young panicles,the total nitrogen,soluble sugar content and the nitrate nitrogen content of root bleeding fluid in different panicle-type varieties increased significantly,which is an important indicator of young panicle development.The level of carbon and nitrogen compound content is GWS 15>Songjing 9>Dongnong 7366>Longdao 27>GWS14>Longdao 5;Plant total nitrogen and soluble sugar content,root bleeding sap nitrate nitrogen content in different panicle-type cultivars increase when nitrogen is added outside the roots,the response of fewer-grain varieties was higher than that of more-grain varieties,and multi-grain varieties had the weakest response.Under the condition of increasing the density in the hole,plant carbon and nitrogen content decreased,the response of multi-grain varieties was stronger than that of more-grain varieties,and the fewer-grain varieties were the weakest.(4)There are significant genetic differences in young panicle antioxidant enzyme activities between different panicle types during panicle formation.The order of SOD and POD activities is GWS 15>Songjing 9>Dongnong 7366>Longdao 27> GWS 14>Longdao 5;the antioxidant enzyme SOD and POD activities of different panicle varieties increased under the condition of adding nitrogen fertilizer outside the root,and the response of GWS 14 was the strongest.Under the condition of increasing the density per hole,the antioxidant enzyme SOD and POD activities decreased,the response of multi-grain varieties was the strongest,and the response of fewer-grain varieties was the weakest.(5)There are great genetic differences in the content of zeatin nucleoside in young panicles of different panicle-type cultivars during panicle formation.The order of zeatin nucleoside content is GWS 15>Songjing 9>Dongnong 7366>Longdao 27 >GWS 14>Longdao 5;the zeatin nucleoside content of different panicle varieties increased under the condition of increasing nitrogen fertilizer outside the roots.Among them,the fewer-grain varieties had the highest response,and the multi-grain varieties had the weakest response.The content of zeatin nucleoside in young panicles was decreased under the conditions of the density in the hole,the response of multi-grain varieties was the strongest,and the response of fewer-grain varieties was the weakest.(6)There are great genetic differences in the transcriptional expression level of young panicle differentiation-related genes Os CKX5,Os CKX9,Os RR2,Os RR5,Os LOGL2 and Os LOGL3 between different panicle-type cultivars at the young panicle formation period,and the expression level is GWS 15> Songjing 9>Dongnong 7366>Longdao 27>GWS 14>Longdao 5.Increasing nitrogen fertilizer up-regulated the transcriptional expression of young panicle differentiation-related genes Os CKX5,Os CKX9,Os RR2,Os RR5,Os LOGL2 and Os LOGL3,and the fewer-grain varieties had the strongest response,while the response of multi-grain varieties was the weakest.Increasing the density in the hole would down-regulate gene transcriptional expression.The multi-grain varieties had the strongest response and the fewer-grain varieties had the weakest response.