Study On High Yield Population Quality Characteristics And Regulation Of Peanut Under Single-seed Precision Sowing

Compared with the traditional planting of two or more seeds per hole,single-seed precision sowing can reduce competition among plants,give full play to the advantages of single plant and optimize population quality.It is an effective planting method to achieve high yiled and increase efficiency of peanut.At present,the high yield technology of single-seed precision sowing has been relatively mature,however,its theoretical system needs to be improved,especially the regulation effects of different plant types,nitrogen fertilization and other aspects on population quality of single-seed precision sowing are rarely involved.Therefore,the population quality indexes were screened out through the high yield demonstration experiment,and then compared with the double seed sowing,the high yield population quality characteristics of single-seed precision sowing were explored;The regulatory effects of different plant types,planting densities,nitrogen fertilizer levels and their interaction on peanut population quality and nutrient accumulation were explored from the aspects of plant growth and development,physiology,biochemistry and molecular mechanism with the methods of field slicing,enzymology,isotope tracing and transcriptome sequencing.And theoretical basis and technical support were provided for the healthy development of single-seed precision sowing technology of peanut.The main results were as follows:1.Population quality indexes of high yield peanutThe difference of peanut population quality under different yield levels were analyzed.The results showed that:The characteristics of high-yield population quality of peanut were high leaf area index,long duration of high value leaf area,more lateral branches,more dry matter and nitrogen accumulation after pod setting,high harvest index and grain leaf ratio,and multiple pods and double kernels.Among these,the leaf area index,the number of lateral branches,the number of pods per hectare and the rate of double kernel pods could be used as important morphological indexes to evaluate the quality of the population.The dry matter and nitrogen accumulation after pod setting（especially at pod fulling stage）could be used as physiological indexes of population quality.2.Quality characteristics of high yield population of peanut under single-seed precision sowingCompared with double-seed sowing,peanut under single-seed precision sowing had higher leaf area index,leaf photosynthetic rate,chlorophyll content and pods weight/leaf area;In the middle and late growth stage of peanut,the dry matter weight of single plant and population were higher.There were more pods per plant and per hectare,and the pods yield was higher The leaf area index,leaf dry weight of upper and lower layers and stem dry weight of lower layers of single plant and population were significantly higher than those of double-seed sowing at pod setting stage;The total root dry weight,root length,root surface area and root volume of single plant and population were higher than those of double-seed sowing,and the proportion of middle and lower layer roots were higher.Compared with double-seed sowing,the differentially expressed gene in leaves were mainly in the processes of redox reaction and protein phosphorylation,and the activities of oxidoreductase,ATPase and nucleoside triphosphatase were strengthened.3.The regulation effects of density on population quality and nutrient accumulation of peanut with different plant typesBased on the characteristics of high yield population quality of single-seed precision sowing,the erect peanut variety“Huayu 22”and semi creeping peanut variety“Huayu 9513”were used and three densities of 75000 plant hm^-2（D1）,150000 plant hm^-2（D2）and 225000plant hm^-2（D3）were set,and the regulatory effects of densities on the population quality and nutrient accumulation of peanut with different plant types were studied.The results showed that:The density tolerance of semi creeping peanut variety“Huayu 9513”was poor than the erect peanut variety“Huayu 22”.“Huayu 9513”had less accumulation of dry weight,nitrogen,phosphorus and potassium,and poor population quality under high density.The plant type index of“Huayu 9513”decreased at high density,which means the development of lateral branches was restricted.The optimum planting density under the current planting mode was lower than“Huayu 22”.At the same density,"Huayu 9513"had higher leaf area,leaf area duration,number of lateral branches,root length,root surface area,root volume,but had less distribution of dry matter to pods,lower harvest index and grain leaf ratio,lower effective branch ratio,fewer pods per hectare and lower pod yield.Transcriptome results showed that:the higher the density,the more the number of differentially expressed genes were in the leaves of the two peanut varieties.And the differentially expressed genes of the two varieties were mainly concentrated in flavonoid biosynthesis,carbon fixation in photosynthetic organs,amino sugar and nucleotide sugar synthesis,etc.4.Effects of nitrogen fertilizer and density on population quality and nitrogen accumulation characteristics of peanutAfter exploring the population quality difference of peanut with different plant types,erect peanut“Huayu 22”was taken as the tested peanut variety,and three nitrogen fertilizer levels 0（N0）,60（N60）,and 120（N120）kg hm^-2,and three planting densities 79300（D1）,158600（D2）,and 237900（D3）plants hm^-2 were set,and ¹⁵N isotope tracing technique was used to study the regulation effects of nitrogen fertilizer and density and their interaction on population quality and nitrogen accumulation and distribution of peanut.The results show that:With the increase of nitrogen fertilizer level,the leaf area index,the activities of SOD enzyme in leaves,the dry matter weight of vegetative organs to reproductive organs of peanut increased,while the effective branch ratio and the harvest index decreased.Increasing the application of nitrogen fertilizer could significantly increase the accumulation of fertilizer nitrogen in the plant,but reduced the absorption of other nitrogen sources such as soil nitrogen and nodule nitrogen,and the differences of total nitrogen absorbed by plants waere not significant.The activities of SOD enzyme in leaves,the number of lateral branches per plant and the first internode thickness of the main stem,root dry weight,root length and other root indexes,root shoot ratio,the dry matter weight of vegetative organs to reproductive organs decreased with the increase of density,but the number of lateral branches and root index of population,and pods yield increased.The nitrogen content of plant decreased with the increase of density,but increasing nitrogen fertilizer could delay leaf senescence.Under suitable nitrogen fertilizer(60 kg hm^-2)and planting density(188000plants hm^-2),the individual was strong,the population quality was good,and the yield was high.To sum up,compared with double-seed sowing,peanut under single-seed precision sowing had strong individuals,reasonable population structure,more photosynthetic products accumulated in the later stage of growth,high harvest index,strong source,large sink and smooth flow,which was the physiological basis of high yield.The ways to further improve the single-seed precision sowing technology were as follows:first,plant type regulation,and reasonable dense planting and appropriate sparse planting should be adopted for erect and semi creeping peanut respectively;Second,the fertilizer density should be coordinated.It should be thin when the nitrogen was high and dense when the nitrogen was low.The mechanism of achieving the same goal through different paths was to improve the photosynthetic performance after pod setting,especially the pod fulling stage,prolong the leaf functional period,and promote the accumulation and distribution of dry matter,which was also the core strategy for the optimal control of the population quality of single-seed precision sowing.