| Paeonia suffruticosa Andr.is a plant belonging to Paeoniaceae,Paeonia and Sect.Moutan,is a unique and valuable woody flowers in China,known as "Exceptional beauty" and "the king of flowers" nicknamed.Peony has a wide range of ecological adaptability under long-term natural hybridization and artificial cultivation.Hunan Province is one of the natural distribution areas of peony in China,and also one of the main producing areas of medicinal peony in China.At present,under the humid and hot climate in Hunan,there are still many problems in the cultivation,planting,garden application and promotion of peony.The origin of peony and the relationship between varieties in Hunan province have not been well solved.Therefore,based on the investigation of peony resources in Hunan province,this study collected and conserved peony resources in Hunan province;Analyzed genetic diversity and genetic relationship of peony in Hunan province by SSR molecular marker technology;Carried out comprehensive evaluation of ecological adaptability;Measured the physiological response of Peony under high temperature stress and the effect of spraying exogenous substances of different concentrations on heat tolerance of Peony under high temperature stress.The main results are as follows:(1)Native peony in Hunan province has 30 varieties and one wild species.Through field investigation,only 17 of the 23 original varieties were found,6 of which had been lost or died.In addition,13 new mutant lines were found in the investigation.The main characteristics of native peony in Hunan Province are:(a)It is an excellent g roup with high temperature and humidity tolerance,and has produced some hybrid or variant varieties in the long history of cultivation.(b)The flower types are not abundant,and the single petal type accounts for 50.00%,while Huandred-Petals Subsection type,Crown subsection type and Proliferate-Flower type account for 16.67%respectively in the double petal type.(c)A single pattern.There are four color lines,among which pink line is the most,accounting for 33.33%;white line is the second,accounting for 25.00%;purple series is relatively small,accounting for 16.67%;rose and purple red varieties are the least,accounting for 12.50%.(d)The whole flowering period was earlier and there were no late-flowering varieties.(2)There are 136 varieties of introduced peony resources in Hunan province.They mainly come from six main producing areas of peony,among which the most peony varieties are in Central Plains(82),followed by Japanese peony varieties(32),then Jiangnan peony varieties(13),European and American peony varieties(6),Western Hubei peony varieties(2)and Southwest peony varieties(1).The main characteristics of introduced peony in Hunan are:(a)Rich in color,a total of 9 flower colors;(b)Comprehensive flower pattern,basically covering all flower types of peony(9);(c)Florescence is dominated by mid-florescence(41.18%);(d)The best adaptability in Hunan province is Jiangnan Peony Variety Group,Southwest Peony and Western Hubei Peony Variety Group also has better performance,and Central Plains Peony Variety Group adapts well.There were significant differences in sexual performance.(3)SSR molecular marker analysis showed that Peony in Hunan province had high genetic diversity.Using 14 pairs of primers for SSR molecular marker analysis,clear bands(115~379 bp)were amplified peony samples in Hunan province,with good repeatability and polymorphism;the average allele variation range of peony in Hunan province was 1.286-2.643;Shannon’s index(1)was 0.198～0.767;the observed heterozygosity(Ho)variation range was 0.286～0.786,with an average of 0.575.Expected heterozygosity(He)ranged was 0.143～0.464,with an average of 0.309;fixed index(F)ranged was-1.000～0.011,with an average of-0.898.The variation range of intra-population genetic diversity(Hs)was 0.111～0.507,with an average of 0.312;the variation range of total genetic diversity(HT)was 0.354～-0.766,with an average of 0.580;the variation range of inbreeding coefficient(FIt)was-0.258～0.724,with an average of 0.036;the range of gene flow(Nm)was 0.049～0.556,with an average of 0.284;and the variation range of standard genetic differentiation coefficient(GST)was 0.284.0.296～0.824,with an average of 0.461.(4)The origin and relationship of Paeonia sufjfruticosa were determined.Peony in Hunan province belongs to Jiangnan peony variety group;Wild species P.ostiin Hunan province has close genetic relationship with wild Paeonia rockii,Paeonia qiui and P.szechuanica;Native peony Hunan province variety ’Fengdan’ and newly discovered mutant lines have close genetic relationship with P.ostii,Paeonia rockii and Paeonia qiui,which proves that these varieties are long-term natural hybridization or variation varieties.’Fendan’,is a variety introduced to Hunan province from central China in the early years.The’zixiuqiu’(ancient peony of west in Hunan province)is the P.szechuanica ’Pengzhouzi’.The pink double petal varieties in western of Hunan province are a special group with a long genetic distance from wild peony species and all peony varieties.’Cilihong’ has the same genetic basis as the wild peony,and is closely related to the wild peony,so it can be used as the evidence of’cilihong’for the wild peony in Hunan province.There is common genetic background between ’fengdan’and P.ostii,’fengdan’is the cultivar of P.ostii.(5)The comprehensive evaluation system of ecological adaptability of peony varieties in Hunan Province was established by using AHP method,and the comprehensive evaluation model of ecological adaptability was established.The ecological adaptability of 119 Peony Cultivars Growing in typical hot and humid climate was evaluated comprehensively.The comprehensive evaluation of peony ecological adaptability was divided into four criteria levels:growth traits,shape and quality traits,quantitative traits and flowering traits.The 14 indexes with maximum weight of heat tolerance were determined by Delphi method,and the adaptability evaluation of peony cultivars was divided into excellent,good and medium.According to the comprehensive score,7 grade Ⅰ varieties,27 grade Ⅰ varieties,70 grade Ⅲ varieties and 15 grade Ⅳvarieties were obtained.Varieties ranked in grade Ⅰ and Ⅱ are recommended to be preferred in humid and hot areas of Hunan province and South of the Changjiang River.(6)The mechanism of high temperature tolerance of peony was achieved by keeping the total chlorophyll content relatively constant to ensure the normal photosynthesis of cells,increasing the content of malondialdehyde to prevent cell membrane peroxidation and increasing the content of soluble protein to improve the water retention of cells.Under high temperature stress,the total chlorophyll content of Paeonia ostii ’Fengdan’increased slowly,while that of ’Xiangdan’ decreased first and then increased,and the total chlorophyll content of ’Fengdan’ was always higher than that of’Xiangdan’.MDA content increased with the increase of stress time.MDA content of Fengdan increased continuously with the extension of stress time,while that of’Xiangdan’ increased first and then decreased.MDA content of ’Fengdan’ was always higher than that of’Xiangdan’.The soluble protein content of ’Xiangdan’ increased continuously with the prolongation of stress time,while’Xiangdan’ began to show a continuous upward trend,and declined sharply at the later stage of stress;moreover,the soluble sugar content of’Fengdan’ was always high.According to the comprehensive evaluation,the heat resistance of ’Fengdan’ is better than that of ’Xiangdan’.According to the correlation analysis,the four indexes of heat injury index(HII),chlorophyll(Chl),electrolyte permeability(Rec)and soluble protein(SP)can be used as the evaluation indexes of exogenous substances induced heat tolerance of peony seedlings.(7)Spraying exogenous substances can improve the heat resistance of peony to varying degrees.Spraying 100 micromol/L salicylic acid(SA)could reduce the heat injury index(HII),40 mmol/L calcium chloride(CaC12)and 40 mg/L abscisic acid(ABA)of peony,increase the total chlorophyll(Chl),electrolyte permeability(Rec)and soluble protein(SP)content.The effects of SA on heat tolerance of Tree Peony Seedlings Induced by three exogenous substances were the best,followed by CaCl2 and ABA;there was no difference between ’Fengdan’ and ’Xiangdan’.SA can improve the heat tolerance of peony seedlings mainly by alleviating the degradation of Chl under high temperature stress,reducing Rec,reducing MDA content,increasing SOD activity and SP content;CaCl2 can improve the heat tolerance of peony seedlings mainly by alleviating the degradation of Chl under high temperature stress,reducing Rec,increasing SOD activity and SP content;ABA can improve the heat tolerance of peony seedlings mainly by alleviating the degradation of Chl under high temperature stress,reducing Rec and increasing SP content.Improve the heat tolerance of peony seedlings. |
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