The Research On Pathogenicity Of Influence Factors And Division Of Infection Type Of Plasmodiophora Brassicae

The clubroot of cruciferous plants is a soil-borne disease, the disease has increased dramatically after introducing into our country, and disadvantage to cultivate the cruciferous crops. Most domestic research focused on investigation and control, but few studies on infection. In this study, we investigated the environmental factors in different inoculation conditions, the roots of the occurrence of infection for production of seedlings observed to understand the law of rape seedling roots of early infection, combined with the incidence survey to find the causative factors and incidence of root hair infection and the relationship between the situation. At the same time, we tried to use four different host plants to divided the infection type of Plasmodiophora brassicae by infecting the root hair. Main results were as follows:1,Through observing early infection of roots about four host, Fengkang 70(Brassica pekinensis), Huangyoucai(Brassica juncea L.),Baiyoucai(Brassia chinesis var. oleifera) and Chuanyou 21 (Brassica napus L.), the results were as follows:in root infection stage, main infection site of restspores was 0-3cm on host taproot, the root hairs and epidermis containing zoosporangium can be found after 5d, and the number of root hair infection had increased over time and reduced the law again; the infection maximum was discovered after 8d in different hosts; the infection trend between root hairs and epidermis was not entirely consistent; the infection number of root hairs and epidermis was different among different hosts, and the host which has the most infection number was Huangyoucai in four hosts.2,Through observing infection of dormancy spores to root hairs under different impact factors, the results showed that the infection number of root hairs was increased by rot treatment; when photoperiod was extended to 18h, the infection number of root hairs significantly reduced, and infected curve was gently, the time was delayed arriving the maximum infection number, and declined slowly; the infection number of root hairs by spray inoculation was more than mix soil; compared with the pot culture and hydroponic culture, the infection number of the former was much more than the latter, and the appearing time which the maximum infection number was delayed about 1d.In hydroponic culture, root hairs infection still occured when spore concentration is 1×103/ml, the infection number was maximum in spores concentration of 1×105/ml, but the infection number range had little change in 1×104～1×106/ml spore concentration; In pH 4.2～7.7 range, the infection number of root hairs reduced with pH value decreased by hydroponic culture, a few hair infection still occurred in the alkaline environment of pH 7.7, and the relationship of infection number and the pH was linear negative correlation, but the slope was different in different hosts.The best inoculation spore concentration was 1×107/g in pot culture, the infection number of root hairs of four hosts, Huangyoucai, Fengkang 70, Baiyoucai and Chuanyou 21, was 242,224,215 and 185, in which the maximum infection number was Huangyoucai; the pH values of roots hairs infection peak of four hosts were 5.6,4.9,4.9 and 5.6; In alkaline environment of pH 7.7, infection still occurred in an average of 1～3 root hairs.3,Through researching club investigation in pathogenic factors such as different spores concentration, pH value, the results show that the disease index was much more serious as increasing spores concentration in 1×104～1×108/g range, and the situation did not exactly match the root hairs infection. The most serious disease host was Huangyoucai in 1×10/g concentration condition; the optimum pH for incidence was 4.9, the disease index was gradually declined as pH value increase or decrease, and few club was found in pH 7.0 while no club in pH 7.7. The influence of different inoculation method to root hairs infection was more than the incidence condition, but there was little correlation between the infection number of root hairs and the incidence in the optimal infection concentration and pH value.4,According to the difference among infection numbers of root hairs for four hosts by hydroponic culture, the nine different sources of P. brassicae were divided into 4 types. The pathogens extract from Santai rape and Emei baby Chinese cabbage belong to No.2, which can easily infect root hairs of four hosts; the pathogens extracted from Liangshan and Xindu cabbage belongs to No.3, which can easily infect Huangyoucai; the pathogens extracted from Pengzhou cabbage belongs to No.4, which can easily infect Huangyoucai and Chuanyou 21; the rest pathogen materials belong to No.1, which less infects four hosts.