| 論文英文摘要 |
Root rot disease caused severe reduction of rose production, and Phytopythium helicoides is proved as the major causal agent. Zoospore suspension of the pathogen was used to infect roots and
basal stems of potted rose seedlings, and the artificial inoculation test caused root rot and wilt symptoms of the tested plants at 24–40°C with the optimum temperature for disease development at 28–36℃. In the further inoculation test, potted rose seedlings showed no symptom if they were soaked in water for only 1 day or without water. Soaking for 2 days or more will cause disease development, and the longer the soaking days were, the more severe the disease symptoms showed. Furthermore, other test result showed that young seedlings were more susceptible to the pathogen. While 2, 4 or 6 months old of the potted rose seedlings (cultivars: Wannainhong and Puli Star) were inoculated with pathogen, the disease severity indexes were respectively 1.8–2.7, 1.3–1.8 and 0. In all the artificial inoculation test Puli star cultivar were more susceptible than Wannainhong cultivar. For chemical screening, the media containing 0.1-1000mg/L of different chemicals were used to test the inhibition of the linear mycelial growth of the pathogen. The tested chemicals which had the half maximal inhibitory concentration
(IC 50) less than 20 mg/L were fluopicolide + propamocarb hydrocholoride, etridiazole, and metalyxyl-copper; which 20–200 mg/L were monopotassium phosphate and dimethomorph. In the potted experiments, those chemicals mentioned above could significantly reduce the disease severity of rose root rot, and showed high potential for disease management in the field. The results of
field trials showed that fluopicolide + propamocarb hydrocholoride, metalyxyl-copper, monopotassium phosphate, and neutralized phosphorous acid could significantly reduce disease incidence of the field roses. The latter two chemicals had better effects, which could reduce the disease incidence from 23.1% to less than 7.0%. |