Study On Preventing Cabbage Clubroot By Rotating And Intercropping With Buckwheat

Cabbage (Brassica oleracea L. var. capitata L.) is a cruciferous vegetables,and widely cultivated around the world. It has been one of important vegetables in China,and played important role in annual vegetables supply.Clubroot disease caused by Plasmodiophora brassicae Woron. is one of the soil borne disease in the world. The bacteria mainly infected cruciferous crops.In recent years, the incidence of clubroot area had led to a serious decline in output, and even no harvest. Once the soil has been infected by P. brassicae, it will carry bacteria for a long term and will be no longer suitable for planting cruciferae crops. In addition,the bacteria is an obligate parasitic bacteria. It can’t grow on artificial medium, spread very far and fast, and has differentiation of many types, and ptevention to the bacteria also is very difficult.At present, the prevention generally relies on agricultural practices, chemicals agent,disease-resistant varieties,biological control methods. But there are not effective measures.To exploring new methods and technologies to control clubroot has important practical significance. Plants have many antibacterial substances. Grange and Ahmed(1985)had reported that more than 1600 kinds plants had controled pests. China has a vast superiority of natural conditions, and its geographical environment is complex, extremely rich in plant resources which are rich in anti-bacterial plant resources.Buckwheat is Polygonaceae,Fagopyrum Mill. dicotyledonous cereal crops. Zhang Qingping(1992) had found that cropping buckwheatin the ill wheat field can increased production of wheat next year, and Gaeumannomyces diseases also significantly reduced. Wang Libo(2005) and Feng Lisha(2006) also found that buckwheatcan can supress bacteria and fungi in a way.At the same time, we surveied the clubroot-prone areas of Fuling district of Chongqing.and found planting buckwheat significantly inhibited clubroot.In this study, we explored the prevention effect of cabbage rotating and intercropping with buckwheat to the clubroot through natural inoculation in field and indoor artificial inoculation experiments. Phospholipid fatty acids (PLFA) was used to determine microflora in rhizosphere soil of cabbage. Root exudates of buckwheat were collected by nutrient solution culture. The effects of root exudates from buckwheat were studied on the incidence of clubroot. Feasibility of alleviating clubroot through rotating and intercropping system of buckwheat together with cabbgae were tested, and focused on the microflora in rhizosphere soil of cabbage and the root exudates of buckwheat.This will provide a theoretical basis for preventing clubroot by biological pathway.The results are listed as follows:1. Through field Natural inoculation and indoor artificial inoculation experiments, the study tested the effect of cabbage rotating and intercropping with buckwheat on preventing the seedling cabbage clubroot. The test results showed that disease rate of monocropping was 88.5%.in the field experient,the The disease rate of cabbage rotating with buckwheat both were20%.0,and the inhibiting effect were the best on preventing the seedling cabbage clubroot. The disease rate of cabbage intercropping with buckwheat were67.5%,58.0%, and significant higher than rotation.The indoor experiment tested the effects of cabbage rotating and intercropping with buckwheat on plant growth, enzymatic activities related to plant resistance and seedling cabbage clubroot. In comparison with monocropping,intercropping and rotating with buckwheat decreased MDAcontent, the activities of CAT, PODand PPOin leaves and roots, as well as PAL activity in roots.The disease rate of monocropping was 88.5%.The disease rate of rotating and intercropping was22.5%,20.0%,80.0%,87.5%.Through field and indoor experiments, Intercropping and rotating with buckwheat increased fresh weight and plant height of cabbage,and controlled clubroot disease in seedling.2. With PLFA method, there are changes in microbial communities of cabbage rhizosphere soil under intercropping and rotating with buckwheat.The test results showed that intercropping and rotating with buckwheat increased the types and contents of PLFA in rhizosphere soil of cabbage in the field experiment,.The precedence ordering of types of PLFA of intercropping and rotating with buckwheat in rhizosphere soil of cabbage was Intercropping with buckwheat,intercropping with flower buckwheat,rotating with flower buckwheat,rotating with buckwheat,cabbage monocropping.The precedence ordering of contents of PLFA was rotating buckwheat, rotating flower buckwheat,cabbage monocropping,intercropping buckwheat,flower buckwheat intercropping.During the three different periods of indoor experiment, dynamic variations in microbial communities of cabbage rhizosphere soil under intercropping and rotating with buckwheat.For the types of PLFA,the same treatment in different periods, has not a law.In comparison with monocropping,the different treatments at same time,intercropping and rotating with buckwheat increased the types of PLFA in rhizosphere soil of cabbage.the same treatment in different periods,in addition to the total amount of PLFA under intercropping with buckwheat,the other four treatments were increased over time.Different treatment of the same period,the trend is rotating larger than monocropping and intercropping.Through field and indoor experiments, intercropping and rotating with buckwheat increased the types and contents of PLFA in rhizosphere soil of cabbage.3. Root exudates of buckwheat were collected by nutrient solution culture.The effects of root exudates from buckwheat on the incidence of clubroot. weretested,and results showed that root exudates buckwheat can prevent the seedling cabbage clubroot comparing with the control.