Evaluation Of Foxtail Millet Germplasm With Low Phosphorus Tolerance And Genome-wide Association Analysis Of Related Characters

Phosphorus is one of the essential elements for plant growth and development.Two thirds of China’s soil is deficient in phosphorus.Excessive application of chemical fertilizer has caused a series of problems such as environmental pollution while increasing the yield of crops.As a non-renewable resource,phosphate ore will be used up in the next few decades.Therefore,it is imperative to develop new phosphorus efficient crops to ensure national food security.Foxtail millet has the characteristics of resistance to poverty,strong resistance to stress,wide adaptability and small genome,etc.It is one of the ideal materials for the exploration of plant resistance genes and the study of plant resistance mechanism.In this study,the low-phosphorus tolerance characteristics of 308 foxtail millet germplasm resources were evaluated and screened,and their comprehensive mechanisms in response to low-phosphorus stress were explored at the phenotypic,physiological,biochemical and molecular levels.The main results were as follows:1,Through the way of laboratory hydroponic,seedling resistance to low phosphorus foxtail millet germplasm screening and the evaluation of low phosphorus characteristics,adopt comprehensive resistance to low phosphorus index could be divided into eight grade 308 material,the first level is low phosphorus tolerance type varieties(level Ⅰ),have 24 varieties,the first 8 is low phosphorus sensitive cultivars(levelⅧ),have 30 varieties.2,Through the way of hydroponic V376 and V254 of low phosphorus tolerance variety,low phosphorus sensitive cultivars V27 and V18 under low phosphorus stress of phenotypic index and physiological index are analyzed,and found that: 1)phosphorus under low phosphorus stress tolerance varieties root elongation,underground part dry weight,root cap ratio increased,root surface area increased,root secrete a large amount of acid phosphatase;2)the activities of SOD,POD and CAT enzymes related to the scavenging capacity of reactive oxygen species were almost stronger than those of phosphorus-sensitive varieties.The inhibition effect of low phosphorus stress on class II low-phosphorus tolerant variety V376 was significantly smaller than that of V27 on class Ⅷ.MYB transcription factor genes seita.3g278400.1,seita.2g168900.1,WRKY transcription factor seita.1g036000.1 and phosphorus transporter SiPHT1;1、SiPHT1;2、SiPHT1;3、SiPHT1;4、SiPHT1;8、SiPHT1;12;There were significant differences in gene expression levels between different varieties and at different stress time points.Compared with V27,the expression levels of phosphorus transporter and transcription factor genes in V376 root system were significantly up-regulated.3,Using cover millet genome-wide SNP marker 1410570 high quality and high polymorphism of 308 corn seedling stage 17 traits(chlorophyll,plant height,leaf length,leaf width,leaf area,fresh weight,on the ground,underground fresh weight and root cap ratio,root length,total projection area,total surface area,average diameter,root volume,root number,branch number,the number of cross,the characteristic coefficient of resistance to low phosphorus)analysis of genome-wide association(GWAS),found in P <0.0001 significant level,detected 96 significantly associated markup.4,The phytozome database was used to locate the candidate genes in the regions of 50 kb above and below the extremely significant correlation sites,and 267 candidate genes were screened,among which 203 candidate genes had known functions and 64 genes had unknown functions.Functional annotation involves participation phosphatidyl metabolic pathways and their biosynthesis,promote plant root elongation and anthocyanin accumulation of gene transcription,involved in the process of protein phosphorylation,and some factors such as zinc finger protein genes,the bHLH transcription factor gene family,phosphatase gene,as well as the family of ABC transporters,bZIP transcription factors,ERF05 family of transcription factors and MYB transcription factor etc.5,Haplotype analysis of genes related to phosphorus metabolism.According to genome-wide association analysis,a gene that may be related to phosphorus metabolism was identified by gene annotation.After analysis,it was found that Si7g32390 had multiple haplotypes in some germplasm,and there were nonsynonymous and synonymous variations in all of them.In the future,favorable haplotypes related to low phosphorus tolerance will be identified and low-phosphorus resistant materials will be excavated to provide germplasm resources and molecular basis for the study on low phosphorus tolerance of millet,which is of great significance for the in-depth analysis of the molecular response mechanism of foxtail millet’s tolerance to low phosphorus stress.