| Roses (Rosa sp.), which belong to the family Rosaceae, are one of the most important ornamental flowers in terms of economy and cultural history of humankind, due to their beauty, attractiveness and different usage areas. The emphasis in breeding in the past used to be on ornamental characters like flower shape, flower colour, or scent etc. In recent years inter-qualities, such as, disease resistance against the major pathogens and pestts, cold and drought resistance, and vase life for cut roses, have become increasingly important. Compared with traditional breeding method that is regarded as higher degree of uncertainly of unpredictability, molecular marker assisted selection is supposed to be a more efficient way to enhance and accelerate the breeding process. Genetic maps provide a framework of the chromosomal organization and can be used to identify genetic linkage between markers and desirable traits, to locate single genes, for QTL analyses and serve as starting point for map-based cloning of genes etc. Currently, related research are mainly focused on diploid level, while in this genus polyploidy occurs frequently in wild as well as in cultivated roses. The majority of the wild species are diploid, whereas most cultivated roses are tetraploid or triploid. QTLs are difficult to select for in a highly heterozygous tetraploid genome like that of the cultivated rose. Thus, a better understanding of a genetic linkage map with a tetraploid population and important genes that contribute to desired phenotypes will lead to improved rose cultivars. The main results were shown as follows:1. The present work contains a genetic linkage map for tetraploid roses that was constructed from an F1 segregation population using AFLP and SSR markers on 189 individuals. The preliminary ’Yunzheng Xiawei’ and ’Sun City’ maps consisted of 298 and 255 loci arranged into 26 and 32 linkage groups respectively.2. The recombined parental maps covered 737 cM and 752 cM of the genome respectively. The final integrated linkage map was aligned with seven integrated linkage groups, which had a calculated total length of 874 cM and 295 polymorphic markers, and it had a mean intermarker distance of 2.9 cM.3. A set of newly developed EST-SSR markers that are distributed evenly throughout the mapping population were released. On the final integrated map,108 pairs of newly developed EST-SSR markers provided 149 polymorphic loci, accounting for approximate 50% of the loci. Common SSRs were distributed within the different linkage groups in the present study, and these can be used as anchoring points in the future, while the newly developed EST-SSRs complement them well4. Based on a two-year five times’ field investigation, several QTLs controlling number of flower petals and flower colors were detected. Three QTLs controlling number of flower petals,4 and 2 QTLs controlling flower color yellow and pink respectively were finally detected on the final integrated map. These results will provide basic information for the future rose research work, especially for the flower color related work.Seven QTLs were examined for number of flower petals that explained the variation from 12.1%-68.7%. In addition, the QTL detection for flower color pink and yellow were found stable with high reliability.The results that were produced from a large number of individuals (189) and polymorphic SSR loci (242) will enhance the ability to construct higher density consensus maps with the available diploid level rose maps, and they will definitely serve as a tool for accurate QTL and marker assisted selection. |
PDF Full Text Request