Evaluation And Genetic Diversity Analysis Of Stenotaphrum Trin.Germplasm Resources

St.Augustinegrass（Stenotaphrum Trin.）is one of the import economic grass in south China.There is abundant native St.Augustinegrass in China with great potential of utilization.In view of St.Augustinegrass germplasm resource’s abundant variation and genetic diversity,systematic studies on different levels had been made on morphology,cytology and DNA markers in order to supply the theoretical base of St.Augustinegrass genetic improvement.In the comprehensive evaluation,this study preliminary analyzed the inter-relationship and variation of the green,turf quality,and stress resistance,which included shade,drought and salt resistance,on St.Augustinegrass accessions;meantime,nutrition characteristics of St.Augustinegrass accessions were evaluated their nutrition value assessment system.Excellent accessions had been selected in order to supply foundation for the development,utilization,and breeding new cultivars.The main research contents and results were as follows:（1）The study is to utilize 10 morphological indexes and turf quality,in order to preliminary assessment genetic variation of morphological characteristic among 58 St.Augustinegrass accessions.The results were as fellows:（1）there is rich diversity in morphological index and turf quality of St.Augustinegrassaccessions,all more than10%.（2）Each morphological index had a high correlation,and most of the indexes reached significant（P<0.05）or extremely significant difference（P<0.01）,such as the higher the height of the obtuse leaf and the higher the vegetative branch,the less developed the stolons;the longer the leaf,the thicker the internode and the lighter the leaf color.（3）The accessions of St.Augustinegrasscould be divided into 3 morphological groups by means of UPGMA.There were significant differences in vegetative propagation characteristics of St.Augustinegrassaccessions.The level of growth rate and vertical growth rate showed abundant diversity coefficient,the level of growth,the coefficient of variation was between 31.95%-119.73%,the average was 64.49%;the level of expansion coefficient and the level of growth rate had very significant positive correlation,horizontal expansion coefficient and horizontal and vertical growth rate growth rate were negatively correlated;according to the characteristics of vegetative reproduction by clustering can be divided into three categories:rapid propagation of stolon type,middle type and stolon slow propagation type.St.Augustinegrass genital reproductive characteristics of the correlative indexes showed abundant diversity,the coefficient of variation was from 6.67%to 40.00%,the average was 22.04%;most of the indicators are significant or extremely significant correlation,positive correlation between reproductive branches of each index is very obvious.Forty-one St.Augustinegrass accessions are divided into three categories,some of which like S1,S10,S9 and S26 with high reproductive branches long inflorescence and single spikelet number has more characteristics,cultivate excellent seed production potential.（2）The study was conducted to assess molecular genetic variation and relatedness among 84 St.Augustinegrass accessions.SRAP and ISSR markers were used.28 SRAP primer combinations generated a total of 273 clearly scorable bands encompassing 267polymorphic;percentage of polymorphic loci（PPL）was 97.8%;coefficients of genetic similarity（GSC）among the genotypes ranged from 0.25 up to 0.91,average 0.60;the He and Shannon genetic diversity phenotype index（I）were 0.38 and 0.55.527 bands were amplified by 27 high polymorphism,informative,and reliable ISSR primers,of which19.52 bands per primer;PPL for all accessions was100%;GSC among the genotyes ranged from 0.50 up to 0.88.He and I was 0.38 and 0.56 in average.Based on RAD-seq technology,SNP markers were,for the first time,developed in St.Augustinegrass.A total of 1280873 and 398155 polymorphic SNP sites were discovered by 49 S.secundatum accessions and 8 S.helferi accessions.SRAP,ISSR,and SNP markers all can produce rich diversity bands,the highest is SNP markers,followed by ISSR markers,and SRAP markers produce the least diversity bands.The clustering according to the results of SRAP,ISSR and SNP markers were also related to the geographical origin and species of the tested materials.Therefore,SRAP,ISSR,and SNP all could be applied to detect genetic diversity for St.Augustinegrass.（3）In 70%shading,the most shade resistant St.Augustinegrass germplasm was selected as S23 and the least tolerant was S12.To valuate the water use efficiency of St.Augustinegrass,the most drought resistance was S44,followed by S32,S11,S15 and S19.The worst drought resistance was S21,followed by S22 and S39.At a Na Cl concentration of 185 m M,the salt tolerance of the best followed by S49,S5,S37,S47and S22;the weakest tolerance to salt followed by S36,S35,S17,S19and S57.（4）According to flow cytometry,the ploidy of St.Augustinegrass is very rich,including diploid,triploid,tetraploid,pentaploid,hexaploid,heptaploid and octoploid（5）A total of 22 high nutrient St.Augustinegrass accessions were screened out,which could be used as fodder for the new strain of forage grass.（6）DNA fingerprints of six superior St.Augustinegrassstrains and four cultivars were successfully constructed by using SRAP markers.（7）Using SNP markers and four morphological traits（length of the stolon,height of the erect shoot,leaf length of the erect shoot,leaf width of the erect shoot）for association analysis,41 SNP loci were significantly correlated with morphological(P≤10^-5)in the S.secundatum,while there was no SNP loci significant correlated with morphological in the S.helferi.