| Clubroot is a soil-borne disease caused by the infection of Plasmodiophora brassicae Woron.The plant is susceptible to disease at the seedling stage,and then the main root is swollen,which eventually leads to the dying of the plant,and the pathogen has the characteristics of rapid transmission,long survival time,great harm and difficult control,so it has a good reputation all over the world.Since the introduction of clubroot into China,the rapid development of China's cruciferous crops has increased year by year.With the continuous research on the prevention and treatment of cruciferous clubroot,it is generally believed that breeding resistant varieties is one of the most economical,effective and environmentally friendly methods for preventing clubroot disease.It is not known how strong the resistance to the cultivated varieties is,so how to quickly and accurately identify the resistance of the variety is essential.Therefore,in this paper,cruciferous crops of cabbage were used as experimental materials to study the changes of various resistance indexes of different resistant varieties of cabbage after inoculation with Plasmodiophora brassicae,aiming to find out the differences between different resistant cabbages,and The relationship between the resistance indexes was analyzed,and a set of index system for anti-clubroot of cabbage was established,which provided a reference for the subsequent cultivation of disease-resistant varieties and prevention of clubroot disease.The main findings are as follows:1.Determination of anti-infectance of eleven kinds of cabbage varietiesThe incidence rate and disease index of eleven kinds of cabbage varieties were determined.The results showed that Qinglian cabbage(incidence rate 15.4%,disease index 10.4)and green resistance No.9(incidence rate 18.6%,disease index 12.9)showed resistance Xiyuan No.6(incidence rate 28.2%,disease index 21.3)and No.83(incidence rate 42.0%,disease index 82.9)showed resistance,and Xiyuan No.4(incidence rate 53.6%,disease index 50.0)showed symptoms,CR17-1(incidence rate 100.0%,disease index 89.8),CR17-2(incidence rate 85.0%,disease index 72.2),CR17-3(incidence rate 95.0%,disease index 85.5),CR17-5(incidence rate 100.0)%,disease index 93.2),CR17-6(incidence rate 81.4%,disease index 78.9)and CR17-7(incidence rate 69.3%,disease index 56.3)showed high sensitivity.2.Establishment of early screening methods for resistant varieties(1)Study on early root hairs and cortex infection of different resistant cabbage varietiesThe hydroponic method was used to observe the root hairs and cortex of twelve kinds of cabbage varieties at an early stage.It was found that the root hair infection rate of the susceptible varieties was higher than that of the resistant varieties,and the latter was higher than the resistant varieties,and the infected varieties were infected.The peak was on the 10 th day,and the infection peak of disease-resistant and disease-resistant varieties was 13 th day.The number of cortical infections of susceptible varieties after 16 d inoculation was also significantly higher than that of resistant varieties,and the latter was higher than resistant varieties.Therefore,the root hair infection rate and the number of cortical infestation can be used as indicators of resistance to the evaluation of cabbage resistance.(2)Study on the amount of bacteria in the early roots of different resistant cabbage varietiesThe hydroponic method was used to determine the amount of bacteria in the roots of 12 cabbage varieties in the early stage by RT-qPCR.The results showed that Qinglian Cabbage,Green Resistant No.9,Xiyuan No.6,No.83,Xiyuan No.4,Jing The peaks of Feng 1,CR17-7,CR17-2,CR17-6,CR17-3,CR17-1,and CR17-5 all appeared on the 10 th day,respectively(lgPbDNA=5.35 fg,5.61 fg,5.95 Fg,6.01 fg,6.06 fg,6.10 fg,6.11 fg,6.26 fg,6.60 fg,6.41 fg,6.76 fg,6.84 fg).At the 4th,10 th and 16 th day after inoculation,there was a trend of increasing first and then decreasing,and there were significant differences in the amount of bacteria in the roots of resistant varieties,disease-resistant varieties and susceptible varieties.Therefore,the amount of bacteria contained in the roots can be quantified by qPCR,and the early development state of Rhizoctonia solani in the host root can be traced as an index for evaluating the resistance of cabbage.3.Physiological and biochemical indexes related to clubroot disease of different resistant cabbage varietiesFive cabbage varieties with resistance gradients were selected as the research objects.The hydroponic method was used to determine the changes of POD,SOD and CAT activities in the roots of cabbage,and the content of MDA and soluble sugar after the inoculation of Plasmodiophora brassicae Differences in change.The results showed that:(1)Antioxidant enzyme activity: After inoculation of Plasmodiophora brassicae with different resistance,the activities of POD,SOD and CAT are in the experimental stage,and the resistant varieties are higher than the resistant varieties,the latter is higher than the susceptible varieties,and The difference was most significant at the 10 th day,that is,the activities of POD,SOD and CAT were positively correlated with the resistance to cabbage swollen disease,so POD,SOD and CAT activities could be used as indicators for evaluating the resistance of cabbage to susceptibility.(2)Malondialdehyde(MDA)content: After inoculation of Plasmodiophora brassicae with different resistance,the MDA content in the root is higher than the resistant variety in the whole experimental stage,and the latter is higher than the resistant variety.There is a significant difference,that is,MDA content is negatively correlated with cabbage resistance to clubroot disease,so MDA content can be used as an index for evaluating resistance to cabbage resistance.(3)Soluble sugar content: After inoculation with Plasmodiophora brassicae,the resistant sugar content of the resistant varieties was higher than that of the resistant varieties in the middle and late stages of the experiment,and the latter was higher than the susceptible varieties,and with the infection The increase of time,the more significant the difference,that is,the soluble sugar content is positively correlated with the resistance to cabbage root disease,so soluble sugar can be used as an index to evaluate the resistance of cabbage.4.Construction of indicator system for resistance to clubroot disease in cabbageBy analyzing the resistance index of different resistant cabbage varieties and the correlation of each resistance index,it was concluded that the resistance index and the resistance index were the most closely related to the 10 th day after inoculation of Plasmodiophora brassicae.It is the highest,so we constructed the resistance index of root hair,the number of cortical infestation,the amount of bacteria in roots,POD,SOD,CAT,MDA and soluble sugar in the 10 th day of inoculation of Plasmodiophora brassicae.A system that serves as an early screening for cabbage varieties resistant to clubroot disease.5.Application of the system of cabbage resistance to clubroot disease in cabbageThe system of anti-root disease of cabbage was applied to cabbage with different resistance.The index of the root hair was infected,the number of cortical infestation,the amount of bacteria in the root and the content of MDA and the condition of the host were determined by the indicators in the antagonistic system.The index was positively correlated,and POD,SOD,CAT,and soluble sugar were negatively correlated with the host's disease index. |
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