Studies On The Fiber Properties And Genetic Diversity Of Gerbera Delavayi Franch

The natural cellulose fibres from abaxial side of fireweed(Gerbera delavayi) leaf blade, the shortest of natural textile fiber, is the material of fireweed clothes by minority people using manual twisting and weaving in southwest China, At present, the unique fireweed textile techniques, which date back more than 500, have been included in the intangible cultural heritage of Yunnan and Sichuan Province. Apart from mannual spinning, fireweed has importance of medical and ornamentla. However, previous research found that G. delavayi has not yet to be cultivated by people. Its wild resources have been severely damaged and need protective exploitation urgently.Genetic diversity research is the important basis for the protective development of fireweed, and molecular marker is the ideal method to reveal genetic diversity. Therefore, in this project, the nursery of G. delavayi will be established by 9 populations(SL: Shilin County in Yunnan Province; XP: Xinping County in Yunnan Province; WD: Wuding County in Yunnan Province; FY: Fuyuan County in Yunnan Province; LJ: Lijiang City in Yunnan Province; EY: Eryuan County in Yunnan Province; KY: Kaiyuan City in Yunnan Province; PE: Puer City in Yunnan Province; SDC: Dechang County in Sichuan Province). And then the genetic diversity and genetic structure of G. delavayi will be evaluated by genic-SSR fluorescence markers based on transcriptome data. At the same time, the fiber properties will be evaluated. This project will provide scientific basis for the strategy making in protective exploitation of G. delavayi.1) Fiber characteristics of G. delavayiThe chemical compositions of fireweed fibers were comparable with those of cotton, except for the wax content, which was four times higher in fireweed fibers that in cotton fibers. The fireweed fibers exhibited low values of length(3-8 mm), fineness(0.3-0.5 dtex), tenacity(0.5-0.6 c N/dtex), density(0.9 g/cm3), and crystallinity(14.6%), but similar elongation at break and moisture regain compared with those of cotton. Furthermore, the fireweed fibers showed smooth surfaces, soft textures, and water impermeability. In terms of fiber-collection method, treatment of leaves in a hot bath at 40 °C for 1 min exhibited the highest efficiency. After subjecting to hot bath, fibers showed a 20% decrease in wax content and a higher thermal stability compared with raw fibers. The small size hinders these fibers from achieving the desirable standard of spinning and weaving by modern machine, but the unique cellulose fibers can be used for manual textile application alone or combined with other fibers without any chemical treatment. In the future, high-efficiency fiber collection method, large-size fiber germplasm screening, and unique textile technology for fireweed fiber are potential key research directions.2) Development of Genic-SSR molecular marker in G. delavayiThe Uni Gene(moren than 1000bp) were selected from the transcriptome sequencing data of fireweed leaf blade. 5179 Genic-SSR loci were found by using MISA software, and 3464 pairs of Genic-SSR primers were designed by Primer 3 software. 350 pairs of Genic-SSR primers were selected by using the analysis of loci and primers. 61 primers were selected after the first amplification for the random selected samples(one sample from each population), which the primers were connected with M13 tail. After the second amplification with fluorescent primer and sequencing by 3730 DNA sequencer, 21 Genic-SSR primers which have high specificity and polymorphic were finnaly selected for comprehensive amplification.3) Genetic diversity of G. delavayiAfter neutral test for the gene polymorphism data from 21 pairs of primers, 19 primers were selected for the analysis of genetic diversity and genetic structure of fireweed. A total of 154 alleles detected for 204 individuals in 9 wild populations of fireweed. The average number of alleles per locus was 8. The total of effective allele gene(Ne) was 44.7307, of which the average effective number of alleles per locus was 2.2365. The observed heterozygosity(Ho) and expected heterozygosity(He) were 0.3049 and 0.4649. The average polymorphism information content(PIC) was 0.4317. Of 19 Genic-SSR loci, 7 were high polymorphism loci(PIC>0.5) and 7 were middle polymorphism loci(0.25<PIC<0.5). Therefore, the 19 pairs of Genic-SSR loci showed good polymorphism, which can be used for the population genetic studies of fireweed.The average genetic diversity of nine wild populations was low(Na=3.8596, Ne=2.0548, I=0.7894, Ho=0.3043, He=0.4152). Except XP, the other 8 wild populations have private allele gene(NP), and each population have 5.1111 private allele genes, which showed that each population have genetic variation within population. In addition, the average inbreeding coefficient(FIS) of 9 wild populations was 0.2617, which means the excess of homozygotes. All the nine groups were significantly from the balance of HWE, means that each population does not follow the random mating pattern recently, and the distribution of alleles is not very uniform. Thus, the genetic identity of the 9 wild fireweed populations was relatively high, and the genetic diversity was not very rich.4)Genetic structure of G. delavayiIn the calculation of STRUCTURE HARVESTER, the optimum delta K value is 5, which means these 9 wild populations have five gene pools. When k = 5, the gene of PE population mainly come from 1 gene pool, whereasa the gene of the other 8 populations were were composed of the other four gene pools. This result indicated that there is a obvious genetic differentiation between PE and the other populations. The gene proportion of those 8 populations in each gene pool was relatively uniform. In all, the structure of 9 wild population of G. delavayi is homogeneous.The genetic distance of 9 wild populations are maintained in a low level(mean 0.1169). The UPGMA cluster analysis based on Nei’s genetic distance showed that nine wild populations are divided to three groups, namely PE population located in south Yunnan, LJ and EY populations in northwest Yunnan, and KY, FY, SL, WD, XP and SDC(in south Sichuan) in central Yunnan. Meanwhile, the individuals within 3 groups and within 9 populations have many cross mixing based on individual UPGMA cluster analysis. This result indicated that there is much gene penetration existed within groups and no obvious genetic differentiation between groups.PCo A results showed that PE population(group 1) were separated clearly with the other two groups, indicating that PE and the other 2 groups differences greatly. At the same time, the second group and the third group showed a great deal of cross mixing, indicating that these two groups have high homogeneity and close genetic relationship. The above results are similar to the STRUCTURE and UPGMA results.Mantel test showed that the genetic distance and geographic distance of 9 wild fireweed populations is extremely significant positive correlation(r=0.573), which showed that the geographic distance or geographical isolation(IBD) has significant influence on the genetic distance of fireweed populations.Moleculor AMOVA showed that most of the genetic variation(89.03%) exists in the internal population, whereas 10.97% of the genetic variation exists between populations. This result is similar to the STRUCTURE and UPGMA results. FST(0.1097) show that there is a moderate genetic differentiation between populations. AMOVA of three groups based on UPGMA showed that most of the genetic variation existed within each group(89.41%), while there was only moderate genetic differentiation(FST=0.1059) among the three groups.The nursery of fireweed in the present study will lay the foundation for the bank of key germplasm resources in fireweed. It will provide the plant materals for the screening, cultivation and breeding of excellent fiber germplasm in the future. Meanwhile, the genetic diversity study of fireweed will give the scientific data for the strategy making in protective exploitation of wild G. delavayi resources. What’s more, the transcriptome data can provide reference for the further studies of fiber formation mechanism and fiber related genes. In addition, the evaluation of fireweed fiber properties is useful to the further understanding and utilization of this short natural textile fiber. In all, the project will is of great significance to inherit and carry forward the intangible cultural heritage —— fireweed textile technology.