Preliminary Studies On Rose Breeding To Powdery Mildew(Podosphaera Pannosa) Resistance

The rose is one of the most prominent ornamental plants in the world. Roses have excellent practicabilities as be widely used as cut flowers, pot flowers, garden plants and whose extracts are used in varieties of industries. In practice, about 40% of all fungicides sprayed on roses are for controlling powdery mildew (Podosphaera pannosa var.rosae,syn.Sphaerotheca pannosa). Powdery mildew affects the normal growth of rose plants, reduces the quality of flowers and even destroys plants. In brief, it is the most serious and widespread fungal disease that adversely affects the rose production in greenhouses. The development of cultivars with improved resistance has been a major breeding challenge for a long time. Two of the main facts highly expected by the breeders are a need for more reliable assessment methods for screening and cultivars with durable resistance to powdery mildew. To compare the reliabilities of the three methods, variety reactions of 13 traditional roses,22 modern roses and Rosa×odorata f. erubescens to powdery mildew were studied by analyzing the results of them. Simultaneously, the roses with relatively high resistance were selected. Furthermore, new genotypes were then created by crossing 14 modern roses with 7 traditional roses and 4 wild species.The results are shown as follows:1. Comprehensive conclutions about the resistance of 36 roses were studied by analyzing the results of these three methods (measuring the natural infection rate in the field, the spore-suspension inoculation method and micro-observation method). It is indicated that R.'Regensberg', R.'Sheila's Perfume', R.'Black Magic', R.'Kardinal', R.'Modern Art', R.'Touch of Class'showed more desirable resistance among all the materials.2. A further research of applicability of the three methods was carried out by correlation analysis.The result indicated that it was more scientific to use average of Subordinate Function to evaluate the resistance to powdery mildew in roses.3. In order to obtain novel cultivars with more desirable resistance to powdery mildew, 7 Chinese traditional roses and 4 wild Rosa species were selected for crossing with 14 modern roses. From the above 142 cross combinations,1303 flowers were pollinated,293 fruits,2516 seeds and 167 seedlings were obtained. The 7 obtained F1 hybrids were validated using the SSR molecular marker process. After amplification of 5 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 2 hybrids that had only maternal fragments.The study provided preliminary assessment of resistance to powdery mildew in modern roses and traditional roses. Cross breeding was carried out to create novel cultivars with desirable resistance simultaneously. The research established basis for new rose cultivars culitivation with our own independent intellectual property.