| Wild Allium plants are important plant germplasm resources,as well as important ornamental,medicinal,vegetable and forage plant resources,with great development potential.Allium spicatum Prain is an endemic plant in the Qinghai-Tibet Plateau.At present,the research on A.spicatum is mostly focused on phylogenetic relationships and adaptive evolve,but there are relatively few studies on its genetic diversity and nutritional components.In this study,the genetic diversity,ecological adaptability and main nutrient contents of A.spicatum were revealed by predicting the potential geographical distribution,community structure characteristics investigation,genetic diversity of phenotypic quantitative traits,variation of seed-setting traits,chromosome karyotype analysis,chloroplast genome construction and other studies.The germplasm was screened for domestication and breeding,which provided the scientific basis for the development and utilization of A.spicatum resources.The main results are as follows:(1)Under the current climatic conditions,the dominant climatic factors affecting the distribution of A.spicatum were isothermality(optimum value was44.87),annual mean temperature(optimum value was 3.78°C),annual precipitation(optimum value was 365.69 mm),and max temperature of the warmest month(optimum value was 18.02 °C).A total of 49 species were recorded in the natural populations of A.spicatum,belonging to 29 families and 48 genera.Among them,the most frequent are Asteraceae,Leguminosae,and Gramineae.Most of the A.spicatum in the population are associated species or occasional species.The habitats are mainly shrub grassland,alpine grassland,and gravel slope.The community types are the P.centrasiaticum community,E.nutans community,and O.thoroldii community.The importance value of A.spicatum was significantly negatively correlated with species richness,Shannon-Wiener index,and Simpson index,and significantly positively correlated with species evenness.The species replacement rate of β diversity was faster at 4 300～4 600 m,and the β diversity was relatively low below 4 300 m.The results of this study have important guiding significance for the development,germplasm collection and artificial cultivation of A.spicatum resources.(2)There were large genetic variations and abundant genetic diversity within and among the germplasm populations of A.spicatum.The variation coefficients of leaf number,aboveground stem diameter and spike diameter were within 30%.The variation coefficients of underground stem length,scape diameter,root length,underground stem diameter,root number,leaf width,leaf length and spike length were 30%～50%.The variation coefficients of scape height,plant height,aboveground and underground biomass were higher than 50%.There were extremely significant differences in the 7 fructification characteristics among the natural populations of A.spicatum.And the average phenotypic population differentiation coefficient was 55.49% with a range from 37.30% to 82.35%.Among-population variation was the main source of variation.Dry and fresh weight of spike,length and width of inflorescence and number of spikelet were the most important traits affecting fructification of A.spicatum.Longitude,altitude,temperature and precipitation were the main environmental factors affecting the fructification characteristics of A.spicatum.A.spicatum populations investigated were diploid,and the chromosome numbers were 8,10,and 11.The chromosome karyotype types were 2B,2C,and 1C.The karyotype asymmetry coefficient ranged from 55.29 % to 62.38 %,the length ratio was between 2.96 and 48.60,and the average arm ratio was from 1.22 to 4.09.The evolution degree of A.spicatum in Samada Township of Kangma County was relatively high,and the evolution degree of A.spicatum in Labupu Township of Nanmulin County was relatively low.The results provide a scientific basis for the protection of genetic resources,germplasm screening and artificial domestication and cultivation of A.spicatum.(3)The complete chloroplast genome of A.spicatum which was collected in Sangzhuzi District of Shigatse City is 152424 bp in length,circular in structure,and has four regions including a large single-copy(LSC)region of 82159 bp;a small single-copy(SSC)region of 17587 bp;and two inverted repeats(IR)regions of 26339 bp.The GC content of the genome is 36.90%,and those of LSC,SSC,and IR regions are 34.71%,29.70%,and 42.70%,respectively.The genome encodes 115 unique genes,including 79 protein-coding genes,38 t RNA genes,and 8 r RNA genes.There are 30 codons with RSCU > 1 in the chloroplast genome,and the codon preference ends with U or A.The number of SSRs in the chloroplast genome was 431,and the dinucleotide repeat type was the main type.Studies have shown that there are slight differences in the characteristics and structure of the chloroplast genome sequence of A.spicatum distributed in different regions,which may be an adaptive evolving performance of A.spicatum to adapt to alpine hypoxia and drought habitats.(4)The nutritional types of A.spicatum in natural populations were nitrogen-carbon(CN)type and nitrogen-carbon-ash(CN-A)type,and the grassland nutrient types of the populations were nitrogen-carbon-ash(CN-A)type,nitrogen-carbon(CN)type,carbon-nitrogen(NC)type,and ash-nitrogen(A-N)type.The variation range of ether extract(EE)in different populations was the largest,and the variation range of crude ash(Ash)in grassland mixed samples was the largest.Two principal components were extracted by principal component analysis,and the cumulative contribution rate was 87.87%.The 11 populations were divided into three groups by cluster analysis.A.spicatum is rich in crude protein(CP)and potassium calcium,with low sodium characteristics.Glutamic acid and sulfur-containing compounds(especially dimethyl trisulfide and(E)-allyl methyl disulfide)were the main substances affecting the characteristic aroma of A.spicatum.The research results provide a reference for the further development and utilization of A.spicatum resources. |
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