| Miscanthus lutarioriparius is a native perennial miscanthus species of China,which belongs to family Poceae and Miscanthus Andersson.Due to high resource use efficiency,it is an environmentally benign plant.Among lignocellulosic biomass resources,it has emerged as a leading crop.At present,this precious germplasm resource is basically in the state of semi-artificial and semi-wild in China,and is only used for paper-making.Therefor,the accurate assessment of genetic diversity and structure within and between populations is crucial to explore rational conservation and utilization options.In this study,twenty-two phenotype markers and twenty-seven SCoT markers were used to study the genetic diversity and population structure of M.lutarioriparius including nine populations from major distribution areas in China.The excellent M.lutarioriparius germplasms were evaluated to study the effects of planting density,fertilization and harvest time on biomass yield and characteristics.The main research results and conclusions are divided into five main parts and presented below:There were significant differences in 22 phenotypic traits between and within the populations.The phenotype diversity of M.lutarioriparius was rich,and the coefficient of variation(CV)indexes of the phenotypic characters ranged from 3.17%to 70.47%with the average of 24.00%.The character variation accounted for 36.91%among the populations and 63.09%within the populations.The diversity within the populations was greater than that between the populations.The average of coefficient of phenotypic characters of 9 populations were Pop4>Pop9>Pop8>Pop2>Pop3>Pop1>Pop5>Pop7>Pop6.Nine populations were divided into two groups,the populations from the south of the Yangtze River gathered into group ?,and the group ? comprised of 4 populations collected from north of the Yangtze River The DongTing lake area is an area with highest phenotypic variationIn 2nd part of this study,genetic diversity of nine populations was studied using 27 Start Codon Targeted(SCoT)markers.High polymorphic bands(97.67%),polymorphic information content(0.26)and allele number(1.88)have shown SCoT as a reliable marker system for genetic analysis of M.lutarioriparius.At the species level,the percentage of polymorphic loci(PPL)was 97.2%,Nei's gene diversity(H)was 0.36,Shannon index(I)was 0.54 and Expected Heterozygosity(He)was 0.56.Analysis of molecular variance(AMOVA)has revealed that genetic variation within populations(84.91%)was higher than among populations(15.09%).Moderate level of genetic differentiation was found in M.lutarioriparius populations(Fst=0.15),which was further confirmed by STRUCTURE,principal coordinates analysis(PCoA)and an unweighted pair group method with arithmetic mean(UPGMA)analysis that has also revealed a clear separation between groups of the north and south of Yangtze River.The gene flow of the populations within the respective south and north of Yangtze River area was high,but low between the areas.There was no obvious correlation between genetic distance and geographic distanceThe 3rd part of the study includes comprehensive comparsion and evaluation of nine agronomic traits(stem/leaf ratio,culm wall thickness,plant height,node number,internode length,stem diameter,plant weight,shoot number,nodal tiller number)and six energy-quality traits(water content,ash content,cellulose content,hemicellulose content,lignin content,net caloric value)of 30 M.lutarioriparius accessions.The outcomes of the study have shown that M.lutarioriparius possesses a wide genetic variation,which is evident by the large coefficient of variation 4.155?75.02%of more than 15 traits.These variations were mainly atteibuted by the yield-related traits,which could be explained by their highest cumulative presence 33.34%in the principal components analysis.The accession HUN202 from Li Country was identified as the best germplasm among the 30 accessionsIn the 4th part of this study,experiments were carried out to evalute the effect of planting density and fertilization on biomass production and biomass quality of M.lutarioriparius.Below are the main reseach outcomes of this part:tillers and the yield of M.lutarioriparius increased with the increase of planting density,whereas planting density had no effect on plant height and stem diameter.All growth parameters of M.lutarioriparius across different planting densities achieved the maximum growth in the third growing season.The optimum row spacing was 0.87m,and the optimum plant spacing was 0.87m.Fertilization could increase plant height,stem diameter and subsequently biomass of M.lutarioriparius.The maximum biomass production under fertilization treatment(N0P3K3 was 21747.13kg/hm2),which was 33.95%increase compared with the control.The sequence of the single-factor effect of fertilization on biomass ptroduction was P>K>N,whereas the effect of interaction among various fertilizations on biomass production was NK>NP>PK.Application of fertilizers can increase the content of cellulose,hemicellulose and lignin.The content of cellulose in each treatment varcied from 40.91%to 48.56%.The hemicellulose content of M.lutarioriparius under different fertilization treatments varcied from 25.01%to 28.81%.The N3P3K0 treatment has significantly increased hemicellulose content,and the N4P2K4,N4P4K2 and N4P0K0 treatments have significantly reduced the content of hemicellulose ofM.lutarioriparius.Application of potassicm has significantly increased the lignin content of M.lutarioriparius,whereas the lignin content in other fertilization treatments did not differ significantly compared with the control.For targeted yield and lignocellulose content,the most appropriate amount of fertilizer application was:Urea(55.08-193.89kg/hm2),Ca3(PO4)2(69.39-117.29kg/hm2),K2SO4(149.46-211.86 kg/hm2)According to the results,the biomass of M.lutarioriparius decreased with the delay in harvesting time,which was mainly due to reduced proportion of leaves.With the delay in harversting,moisture,ash,and hemicellulose contents were significantly decreased.Whereas cellulose,lignin contents and calorific value was significantly increased.Most of mineral elements of M.lutarioriparius have decreased with the delay in harvesting period,except the content of K and Ca which were increased at first and then decreased.Calorific value was positively significantly correlated with cellulose and lignin contents,and was significantly negatively correlated with hemicellulose contents.The ash content was significantly positively correlated with content of K and Ca.Delayed harvesting reduced the biomass of M.lutarioriparius,but significantly improved its fuel quality.M.lutarioriparius fuel quality was better when harvested in November to next JanuaryOverall,the study has showed that there were abundant genetic diversity and moderate genetic differentiation in M.lutarioriparius,which could be explainted in different way to screen out excellent germplasm resources depending on utilization pathways.Furthermore,the outcomes of this have shown that the biomass yield and quality of M.lutarioriparius can be improved through cultivation techniques.This study provides valuable guidance for the development of M.lutarioriparius and comprehensive future utilization options. |
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