Germplasm Resistance Identification And Resistance Mechanism Against S. Sclerotiorum In Heading Chinese Cabbage

In recent years,the occurrence of Sclerotinia sclerotiorum in heading Chinese cabbage has been frequent,which has caused huge losses in the yield of Chinese cabbage.There are few studies on the identification methods for disease resistance to Sclerotinia sclerotiorum and the identification of germplasm resource in heading Chinese cabbage,which limits the progress of breeding of Chinese cabbage antibacterial nucleus diseases.In order to establish a rapid and accurate method for identifying the resistance of Chinese cabbage germplasm to Sclerotinia sclerotiorum,and screen resistant germplasm resources for disease resistance breeding,the identification method and resistance mechanism of Chinese cabbage to Sclerotinia sclerotiorum had been studied,which laid a theoretical foundation and technical support for the study of resistance breeding and disease resistance mechanism of Chinese cabbage to Sclerotinia sclerotiorum.The results obtained were as follows:1.The method for identifying the disease resistance to Sclerotinia sclerotiorum at seedlings in Chinese cabbage was established.The optimal inoculation size of hyphae agar block is 5 mm diameter,the optimal inoculation seedling is three-leaf-stage and the optimal culture temperature is 25 °C.2.15 resistance lines,28 tolerance lines,37 susceptible lines and 18 high susceptible lines were identified from 98 Chinese cabbage lines.There are resistant lines in Chinese cabbage,which can be used for breeding of resistant varieties.3.The relationship between SOD activity,GSH and MDA content and disease resistance to Sclerotinia sclerotiorum in Chinese cabbage has been confirmed.The activity of SOD in each material increased first and then decreased after inoculation.The peak time of SOD activity of each material was different.The SOD activity of resistant material was higher than that of moderately resistant and susceptible materials all the time.The GSH content of the three materials showed different trends after inoculation of Sclerotinia sclerotiorum.The GSH content of resistant material 15S94 generally showed an upward trend after inoculation.The moderately resistant material 14S474 showed a trend of rising first and then decreasing,and the susceptible material 17S20 rose first and then fell.The MDA content of the three materials showed an increasing trend after the inoculation of Sclerotinia sclerotiorum.The MDA content of the resistant material 15S94 was lower and the increase rate was lower than that of the other materials,and the change of the susceptible material was the largest.4.The antibacterial effect of salicylic acid(SA)on the Sclerotinia sclerotiorum of Chinese cabbage and induced disease resistance to Chinese cabbage were confirmed.The inhibition of mycelial growth was more obvious and the number of sclerotia in the single medium decreased with the increase of SA concentration in the medium.Mycelial growth was abnormal or even not growing when the concentration of SA in the medium was higher than 0.08 mg/mL.Exogenous application of SA can induce the resistance of Chinese cabbage to Sclerotinia sclerotiorum.With the increase of SA concentration and treatment time,the resistance of Chinese cabbage to Sclerotinia sclerotiorum was enhanced.The optimum concentration of exogenous SA to improve the resistance of Chinese cabbage seedlings to Sclerotinia sclerotiorum was 0.6 mg/mL,which can improve the disease resistance of seedings with little damage to seedlings.