Studies On Diseases Species Of Major Flower Plants In Shanghai And Root Rot Of Gerbera Jamesonii

In recent years, Shanghai has become the major flower production base in China.With the changes of flower species and climate, diseases of flower plants changed. In2006-2007, we made a filed survey of major flower plants diseases in Shanghai and asystematic research about root rot which was a serious disese of Gerbera jamesonii.1. The disease species of major flower plants in ShanghaiFifty-five species of disease were found in thirty-six species of major flower plants inShanghai. Among them five species of disease were new domestic records in Shanghai.According to the investigation results, a list of disease in these flower plants was made.2. The studies on root rot of Gerbera jamesoniiThe pathogens of root rot of Gerbera jamesonii was identified as Phytophthoracryptogea based on its morphological characteristics, pathogenicity and sequence ofribosomal DNA-ITS. The results of biological characteristics indicated that the optimummedia for mycelia growth was V₈ and CA; the optimum pH and temperature for myceliagrowth were 6 and 25℃, respectively. Light intensity give no significant influence onmycelia growth. The lethal temperature for mycelia growth was 44℃.Both of the percentage of activation and death enhanced gradually with oosporesculture age prolonging. The percentage of activation was 26.4% when the oospores were60 days old and it was the highest one. And then, the percentage of activation decreased.The dormancy declined gradually. The percentage of activation of oospores pretreated with35℃for one day was 37.2%, the highest one. H₂O₂ treatment lightly affected viability ofoospores.After Gerbera was inoculated by Phytophthora cryptogea, the activity of PO,PAL, PPO and SOD changed subsequently. The activities of PO,PAL,PPO and SOD wereincreased after inoculation and reached the maximum after 5-7 days.The bioassay of 7 fungicides against Phytophthora cryptogea at 3 different fungalgrowth stages was investigated in vitro. The results showed that Dimethomorph andMefenoxam&Mancozeb was able significantly to inhibit the mycelial growth, and their50% effective concentration(EC₅₀) values were 0.58,1.46μg.ml^-1, respectively.Famoxadone & Cymoxanil,Mefenoxam & Mancozeb and Propamocarb hydrochlorideinhibited the formation of pathogen sporangium,and their EC₅₀ values were 0.48,0.82,1.00μg·ml^-1, respectively. The values of EC₅₀ of Propamocarb hydrochloride,Dimethomorph,Mefenoxam&Mancozeb and Famoxadone&Cymoxanil against zoosporegermination were 0.82,0.89,1.09,1.60μg·ml^-1, respectively. Oxadixyl & Mancozeb,Chlorothalonil and Mancozeb only gave low inhibition to pathogen at 3 growth stagestested.