Analysis Of Genetic Relationships Between Wild Species And Chinese Traditional Roses And Powdery Mildew Resistance Breeding

The rose is one of the most prominent ornamental plants in the world.Roses are widely used as cut flowers and pot flowers,as well as garden plants,and whose extracts are used in a variety of industries. With over 2000 years of cultivation history,China has been a main distribution centre of the genus Rosa L.and holds 95 shrubs species,which includes 65 endemic in total.However,due to serious damages to natural habitats,ambiguous nomenclature,a complicated genetic background,and inadequate investigation into germplasm resources,the progress of researchers in breeding and exploitation were severely restricted.Chinese traditional roses,with favorable features such as strong disease resistance, adaptability and fragrance,have preserved up to now.R.chinensis 'Slater's Crimson China',R. chinensis 'Parsons' Pink China',R.odorata 'Hume's Blush Tea-scented China' and R.odorata 'Parks' Yellow Tea-scented China' have played a foremost role in the breeding development of modern roses. Therefore,in order to protect Rosa resources,conserve genetic diversity and classify different rose species,this research continued for three years and focused on the investigation,evaluation on the wild and cultivar Rosa resources,as well as their genetic relationships by using phenotypic,palynology,SSR molecular markers and nrITS sequence processes.The wild resource investigations were conducted in Northwestern Yunnan and Southwestern Sichuan areas where Rosa is concentrate distributed,Ili and Altay in Xinjiang,Changbai Mountain and Beijing suburban areas that all have distinctive rose resources.Furthermore,powdery mildew resistant plants were selected among the wild species and traditional roses as parents based on the resource evaluation,and new genotypes were then created by crossing with modern roses.The results are shown as follows:1.After 3 years of field survey in the areas mentioned above,43 Rosa species and 7 varieties belonging to 7 sections and 7 series were located and collected,these account for 44.8%of the total species number in China.The geographic distribution of Rosa featured a broad altitude range (700-4300m).Species such as R.orneiensis,R.soulieana,R.longicuspis,R.davurica and R.sertata, with strong adaptability and abundant variation,are widly distributed.The natural habitats of Rosa, especially in R.prelucens,R.odorata var.gigantean,R.rugosa and R.marretii have been devastated severely and should be protected urgently.A multifactorial appraisal system based on the Analytic Hierarchy Process was applied against Rosa species.10 species including R.moyesii,R.acicularis,R. xanthina et al.were chosen for direct landscape application or crossing parents,while 15 species consist of R.soulieana,R.laxa,R.brunonii could be able to improve their hybrids by some potentially useful characteristics.2.An investigation and arrangement of existing Chinese traditional roses was carried out and 22 traditional Chinese roses were selected.22 rose cultivars and 2 R.odorata were classified by the Q cluster analysis.19 dominate characteristics among 27 were selected under R duster analysis and the principal component analysis.The traditional roses were classified into 4 categories by the differences of plant types and flower traits.3.Pollen morphology of 11 Rosa species and 14 Chinese traditional roses were examined under scanning electron microscope(SEM) for the purpose of systematic observation and comparative analysis.The features of pollen grains were goniotreme,prolate and perprolate.The equatorial view was ellipse,while the polar view was 3-1abed rounded with 3 narrow opereulums annularly distributed in equal space.Exine sculpture was striate with apertures.The pollen type was N₃P₄C₅ model.Variability among species and cultivars were showed by the features of the exine sculpture.The exine sculpture was mainly stripy,and the tested pollens could be divided into five categories according to the orientation,thickness,distance and density of the stripes.The results of cluster analysis indicated that the size and exine sculpture of pollen could reflect the differences between sections to a certain degree. According to the evolution of rose pollen,it can be inferred that sect.Pimpinellifoliae is more primitive than sect.Cinnamomeae,and sect.Synstylae,sister to sect.Chinensis,are more evolutive.R.chinensis 'Parsons' Pink China',R.chinensis 'Slater's Crimson China' and R.chinensis 'Pu Fu Hong' were more evolutive than other cultivars,while R.chinensis 'Si Mian Jing' could be regarded as an original cultivar.4.SSR reaction system for Rosa was established and the suitable SSR primers were screened.64 resources were amplified by fluorescence quantitative PCR(FQ-PCR) with 12 pairs of primers.All mierosatellite markers showed a high level of polymorphisrn(4-15 alleles per microsatellite marker, with an average of 9.7 per locus).The fragment sizes ranged between 100-400bp.Cluster analysis revealed that Chinese traditional roses showed close genetic relationship with sect.Synstylae and sect. Chinensis,while showed dissimilarity with sect.Banksianae,sect.Cinnamomeae,sect.Microphyllae, sect.Pimpinellifoliae,and sect.Laevigatae.Meanwhile,R.multiflora,R.odorata var.erubescens formed a branch with modern roses.R.prelucens in sect.(endemic species in Yunnan) were in the same cluster with R.rugosa and R.davurica(both in sect.Cinnamomeae),while showed dissimilarity with R. roxburghii(sect.Microphyllae).Moreover,the rest of the cluster results coincided with traditional botanical classification.5.A further research of genetic relationships among Rosa L.was carried out by nrITS sequences. 36 ITS sequences were registered in GenBank and the accession number was FJ527684-FJ527719.In all species and cultivars,the length of ITS was 622-628bp,including 85 parsimony-variable sites and 42 parsimony-informative site,which were account for 13.5%and 6.7%respectively.The G+C content varied from 55.9%to 58.4%.The main variation of ITS sequences in Rosa was ITS1.In the ITS analysis,Chinese traditional roses,sect.Synstylae and sect.Chinensis comprise a single group,which agreed with the results of SSR molecular marker analysis and showed strong effects on the development of traditional roses.While R.prelucens and R.roxburghii(both in sect.Microphyllae,) were clustered together with wild species from sect.Cinnamomeae,which indicated that there was close genetic relationship between them.This result did not fully support the classification of the genus Rosa. Meanwhile,R.banksiae formed a single group by itself showed larger genetic distance with other groups.6.Resistance of 31 Rosa species and traditional roses to powdery mildew was studied by measuring the natural infection rate in the field.The results indicated that the resistance abilities varied among different materials.5 wild species were found to be highly resistant,while another 18 showed above-average resistance.11 traditional Chinese roses were selected for crossing with 6 modern roses with good ornamental characteristics but low resistant.From the above 44 cross combinations,563 flowers were pollinated,and 158 fruits were obtained from 29 hybrid combinations.The seed setting rate was 28%.The 10 obtained F1 hybrids were validated using the SSR molecular marker process. After amplification of 6 specific fragments,the results showed strong similarity with both parent fragments,thus demonstrating strong evidence of true hybrids.Further research is needed for the morphology identification with the other 4 hybrids that had only maternal fragments.The study provided the theory basis for the resource investigation,protection and utilization, genetic relationships analysis of genus Rosa L..Moreover,the research eatablished a material basis for new rose cultivars culitivation with our own independent intellectual property.