| The low-phosphorus?LP?stress is a global problem for foxtail millet production and has been exacerbated by breeding activities that have been reduced the genetic diversity of foxtail millet.It is very important to evaluate the tolerance of foxtail millet.In this research,160 core accessions?from 5 different countries and 20 different regions of China?were evaluated for LP tolerance during the seediling stage under 3 Pi conditions.Plant height?PH?,Leaf length?LL?,Leaf width?LW?,Root length?RL?,Stem diameter?SD?,Dry weight of shoot?WS?and Dry weight of root?WR?and Root-shoot ratio?RSR?8 agronomic traits were analysed.In advance,we compared the root architechture between the sensitive varieties and the tolerant varieties under different Pi conditing.Genome-wide association analysis of natural populations?287 core collections?containing pre-test materials materials,based on a total of 14191 high-qualities and highly polymorphic SNP markers covering the whole genome of 9 chromosomes of the foxtail millet,were conducted to protest the genes to control the phenotypic traits.The significant association sites related to plant height,leaf length,leaf width,root length,stem diameter,dry weight of shoots,dry weight of roots and rootshoot ratio and their resistance to low phosphorus were detected under different phosphorus environments.The candidate gene locients resistant to low-phosphorus traits and low-phosphorus tolerance were also excavated,and excellent allelic variation in significant associated sites was analyzed.The genetic variation that determines the phenotypic variation of foxtail millet was preliminarily determined and molecular marker information and excellent carrier materials are also provided for the resistance and high-quality breeding of millet.The main findings were as follows:In this study,membership function analysis were carried out on 13 indicators of 160 core foxtail millet varieties,and soil cultured under low phosphorus?LP?and normal phosphorus supply?NP?conditions.The hydroponic test was used to screen low phosphorus tolerance varieties.There were 9 varieties with low-phosphorus tolerance,46 varieties with a litte low-phosphorus-tolerant,41 varieties with medium low-phosphate tolerance,47 varieties with a litte low-phosphorus-sensitive,and 17 varieties with low-phosphorus sensitivity.Furthermore,a soil culture experiment was conducted to cultivate selected varieties with 5 lowphosphorus sensitivity and 4 low-phosphorus tolerance under low phosphorus?LP?and normal phosphorus?NP?conditions.It was found that there were the root surface area,root volume,total root length and number of lateral roots of the four low-phosphorus-tolerant varieties were larger than those of the NP environment in the LP environment.The four traits of the five low-phosphorussensitive varieties were not necessarily greater than the NP environment in the LP environment.The root diameter of each variety is greater than the NP environment in the LP environment.There were 287 materials divided into two groups,Subgroup 1 and Subgroup 2.Subgroup 1 contains 115 varieties,and Subgroup 2 contains 172 varieties.Since the ratio of the relationship between any two materials in the population is 0-0.1,it was 72.25%.Therefore,most of the materials in the population are not related or weakly related,which is a good material for correlation analysis.In order to comprehensively evaluate the low phosphorus stress response to seedling millet by whole-genome correlation analysis,there were 287 core collections were selected and cultured in 3 phosphorus environments trait: E1(0.005 mmol·L-1),E2(0.25 mmol·L-1)and E3(2.0 mmol·L-1)and we measuring the phenotypes of PH,RL,LL,LW,DMS,ADW,UDW and RSR.The 14191 SNP markers were used to correlate with two models of millet phenotype,population structure,genotype and phenotype resistance to low phosphorus,population structure and genotype.The results showed that 84 SNP markers were significantly correlated with 7 traits in different phosphorus environments at the significant level of P<7.047×10-5,and which included 7 SNP markers were detected in multiple environments.A total of 39 SNP markers were detected to be significantly associated with the low-phosphorus tolerance of 6 traits;the phenotypic variation range explained by these significant SNP markers ranged from 6.53% to 12.42%.The attenuation distance of SNP markers was calculated by Linkage disequilibrium?LD?to be 100 kb.The phytozome database was used to locate candidate genes in the 100 kb region the above significant association sites,and 189 genes were obtained,which include.146 functional genes have been obtained.Seven genes Seita.5G236200,Seita.5G237300,Seita.7G023600,Seita.9G553400,Seita.7G082500,Seita.7G166200,and Seita.2G134600 were associated with the phosphorus metabolism pathway,and 43 genes were unknown.There were 7 trait-related and 21 low-phosphorus-resistant factors that can be used to enhance the excellent allelic variation of millet-tolerant to low-phosphorus and their corresponding typical materials were excavated based on the detected significant SNP markers.There were 10 rare excellent allelic variations that can maximize the synergistic effect of low phosphorus tolerance.And the typical materials were V56,V13 and V208.The remaining 18 excellent allelic variants were excellent allelic variations selected by nature,and the typical material with all the excellent allelic variations to RL,LW and UDW was V176,which has all the excellent features in DMS,LL and RSR.Alleles,V164 and V237 have all the excellent allelic variations in RL,DMS and RSR,and V84 has all the excellent allelic variations in LL,LW and RSR.We performed an excellent allelic variation analysis on the 9 low-phosphorus-tolerant varieties that had been screened.All of the nine varieties had different numbers of excellent allelic variations selected by nature.These varieties are reliable low-phosphorus materials that have been naturally evolved.Based on the excellent allelic variation of excavation,we predicted that the parental combinations of the six groups for the improvement of low phosphorus tolerance in seedling stage.They were V176×V17,V176×V84,V164×V84,V237×V84,V56×V176 and V13×V176. |
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