| Tree peonies(Paeonia Sect.Moutan)are famous traditional flower in China,which also have important medicinal and oil values.P.rockii(flare tree peony)was one of the wild species involved in the origin of cultivated tree peony in China.As a kind of tree peony germplasm resources with strong resistance to adversity,wide adaptability and great development potential,cultivated P.rockii has formed a cultivar group second only to the traditional P.suffruticosa.In order to fully explore and utilize the germplasm resources,the genetic diversity and causes were revealed by analyzing phenotypic traits,molecular markers and cultivation origin.Furthermore,through association analysis,molecular markers associated with important traits were mined to provide support for molecular-assisted selection breeding.The main results were as follows:1.Based on phenotypic traits,EST-SSR(Expressed Sequence Tag-Simple Sequence Repeat)markers and cp DNA(Chloroplast DNA)sequences,the diversity of 282 cultivars was analyzed.The results showed that the six quality traits varied widely,and the flower color could be divided into six color systems:white,pink,red,purplish red,dark red and blended color.The variation coefficients of 28quantitative traits ranged from 12.32%to 108.72%,and the variation was evenly distributed in the population without obvious hierarchical structure.A total of 185 alleles were detected from 34 EST-SSR,and the average values of heterozygosity,polymorphism information content and diversity index were0.537,0.611 and 0.908,respectively.In addition,all the samples were divided into three groups.The haplotype diversity and nucleotide diversity of 80 cultivars based on the combined fragments of 3 cp DNA sequences were 0.164 and 0.28×10-3,respectively.To some extent,these 282 cultivars can reflect the current genetic variation status of cultivated P.rockii,and can be regarded as the core germplasm resources.2.Thirty-four EST-SSR markers and three cp DNA sequences were used to analyze the genetic diversity of 282 cultivars and 45 populations of 5 wild relatives.The EST-SSR data showed that the genetic diversity of cultivated P.rockii was at a medium level.The cp DNA data showed that 17 of the 45populations had higher diversity than cultivated P.rockii.Further analysis showed that 15 populations of P.rockii subsp.rockii,P.rockii subsp.atava,P.qiui and P.ostii were involved in the origin of cultivated P.rockii.The conservation and utilization of wild resources should be targeted,and the beneficial genetic variation should be excavated to improve the diversity of cultivated P.rockii.3.Using association analysis to find the loci associated with important traits is the basis of marker-assisted selection.Nineteen phenotypic traits and eighty-one EST-SSR markers were used to analyze the association population of 160 cultivars.The results showed that the variation coefficients of phenotypic traits ranged from 11.87%to 110.64%.A total of 493 alleles were detected and the optimal subgroup structure was determined as 3.Most of the markers were in linkage equilibrium by linkage disequilibrium analysis.Based on the single-marker association analysis of mixed linear model,17 significant association combinations of 4 flower traits with 11 EST-SSR and 117 significant association combinations of 10 fruit traits with 32 EST-SSR were obtained.4.According to the gene effects corresponding to the significantly associated locus,P280 and PS64were identified as the combinations of locus for the assisted selection of high yield(individual seed fresh weight)in P.rockii.Aiming at high yield,2 out of 151 candidate clones were screened by using P280and PS64,which laid a foundation for the cultivation of high-yielding tree peony. |
PDF Full Text Request