Study On Main Diseases Of Winter Rapeseed(Brassica Campestris) And Fungicides Selection In Laboratory

1. The pathogen causing downy mildew of winter rapeseed in Gansu Province was identified as Peronospora.parasitica (Pers.) Fr. The pathogen could infect leaves, stem and pods of winter rapeseed and appeared white mould on the surface of infected area. The average incidence and disease index reached32.8%and28.40respectively at harvest stage. In the field, the sporangia of the pathogen was observed in the early April. Around22nd of May, the amount of sporangia reached highest, the average number of sporangia per square centimeter was0.71. When the temperature was16℃and RH was95%, the disease inoculated with pathogen after72h could occur. With the temperature of10.3℃, RH of61.0%and accumulated duration of rain precipitation of1.6mm in five days, the number of sporangia reached0.76/cm2, was the highest. The rotation of wheat-winter rapeseed could reduce the incidence of the disease. There was no significant in different cultivars of the severity of the disease besides Longyou No.9.2. It was determined for the sensitivity of different cultivars of winter rapeseed to the pathogen of downy mildew by using the leaf disc method, the results showed that winter oilseed rape leaves in vitro inoculation were consistent with the field material disease situation, from the morphological features observed on inoculated leaves and in the field of natural infected leaves pathogens, further demonstrate that the pathogen was Peronospora parasitica (Pers.) Fr.; Other cruciferous crops of group of resistance-phenotype to downy mildew of winter rapeseed could be divided into middle resistant(MR) and resistant. Five different cultivars of group of resistance-phenotype to downy mildew of Chinese cabbage and radish could be classified into sensitive (S), whereas to downy mildew of cabbage and Cauliflower could be classified into resistant; It was determined for the sensitivity of five fungicides the downy mildew of winter rapeseed, The fungicides (SYBK and Mancozeb+Cymoxanil) showed strong virulence to downy mildew pathogen, EC50were108and19.20μg/mL, more sensitive to downy mildew of winter rapeseed than other fungicides, such as Propamocarb, and winter rapeseed zineb on downy mildew pathogen were very insensitive. There were significantly positive correlation at pharmacy concentration and inhibition effect, The five fungicides of relative coefficiene was among0.95.3. The incidence of virus diseases of winter rapeseed was surveyed from2006to2008in Lanzhou and Wuwei districts of Gansu Province, the characteristic lesion with mosaic, crinkle and dwarf was produced on infected area, the disease incidence in most oilseed rape fields was less than1%, whereas the incidence in some fields nearby virus sources in the vegetable plots was up to8%-12%. Serological diagnosis of the viruses revealed that the proportion of TuMV was100%, tested by enzyme-linked immunosorbent assay (ELISA); Host range and interaction tests showed that the host range of viruses winter rapeseed is narrow, it could infect Chinese cabbage, radish, cabbage, cauliflower, lettuce, spinach, etc., the symptoms were vein clearing, mosaic and crinkle, but it could not infect cucumber, cowpea and chili. The pathogen of Chinese cabbage, radish, cabbage and cauliflower virus diseases could infect different cultivars of winter rapeseed, which could express mosaic symptoms.4The five pathogens causing root rot of winter rapeseed in Gansu Province were identified as Fusarium semitectum, Alternaria alternate (Fr.) Keissl., F. oxysprorum, Rhizopus nigricans, Penicillium sp., the main pathogens causing postharvest diseases of apricots were F. semitectum and A.alternate, the isolation frequencies of them were47.1%and30.9%, respectively. After artificial inoculation with or without wounds, the incidence of root infected by F. semitectum and A.alternate were90.0%and80.0%, or76.7%and70.0. With mycelium growth rate test method, the toxicity of seven fungicides to F. semitectum and A.alternate had inhibition effect, the result indicated that EC50of Carbendazim, Thiophanate-methyl, Hymexazol, Zineb, Thiram, Thiram+carbendazim and Hymexazol+metalaxyl were17.66、16.89、0.13、1435.20、50.84、59.03and0.53μg/mL,36.06、41.54、0.29、59.30、34.06、109.27and0.81μg/mL, EC50of Hymexazol showed strong inhibitive effects on F. semitectum and A.alternate were under0.3μg/mL. There were significantly positive correlation at pharmacy concentration and inhibition effect, The relative coefficiene was among0.90.