Changes Of Several Defensive Enzymes Activities Of Resistant Cultivar And Susceptible Cultivar Of Arachis Hypogaea After Ralstonia Solanacearum Inoculation

Ralstonia solanacearum is the bacterial wilt pathogen and Gram-negative bacteria. Plants which can be infected by Ralstonia solanacearum cover 44 families, more than 300 species. Solanaceae are the most. Mutiple classification systems of Ralstonia solanacearum exist, two of them are internationally accepted classification systems.: First, Ralstonia solanacearum is divided into 5 types according to host range; Second, 5 variants are divided into based on oxidation capacity using 3 disaccharides(maltose, lactose and cellobiose) and 3 hexanols(mannitol, sorbitol and alcohol Euonymus). Its secretion systems can be divided into 6 types. The major virulence factors of Ralstonia solanacearum are extracellular polysaccharide and extracellular proteins. Because of plasticity of the genome of Ralstonia solanacearum, bacterial wilt is difficult to control. Genome of Ralstonia solanacearum has bipartite genome structure, alternate coden usage region, insertion sequences and transposon. In addition, horizontal gene transfer can happen in he genome of Ralstonia solanacearum.Peanut wilt is a bacterial vascular bundle disease caused by Ralstonia solanacearum. Severe disease hazards happened in China, Indonesia, Vietnam, etc. Affected areas of China are the largest. The incidence rate reaches 30% in the peak period, even 100%.There are many control methods on bacterial wilt, such as the use of resistant varieties and transgenic plants, proper rotation of crops, chemical control and biological control, etc. Breeding resistant varieties widely considered is the most cost-effective method on peanut wilt.Defense systems involved in the process of Ralstonia solanacearum infecting plants are complex. From different angles, these defense systems can be divided into preformed resistance and systemic resistance, non-host resistance and host resistance, seedling resistance and adult plant resistance, etc.The process of plant disease resistance widely Involves plant secondary metabolism, which can be mainly divided into 2 categories, one is antitoxin, which is expressed constitutively, The other one is phytoalexin, which is expressed after microbial infection.The resistance mechanisms of plants is the root cause that plants can survive in the long struggle with plant pathogens, and can coevolve with the pathogen constantly. Cultivating and screening of resistant cultivars and cultivating Ralstonia solanacearum resistant cultivars by transgenic technology are still the cost-effective, user-friendly way to control bacterial wilt.Redox enzymes of plants are participants of plant secondary metabolic reactions, and closely related with plant resistance. PAL is involved in plant chromogenesis, cell differentiation, lignification, disease resistance and regulation of secondary metabolites, etc. Regulation of secondary metabolites includes regulations of compounds of flavonoids compounds, paclitaxel, alkaloid and kalofilum kathing, etc. CAT's main function is to disintegrate H₂O₂, and transform it into H₂0 and 0₂ which are non-toxic. Free radical is seriously harmed, and result in bioactive molecule oxidized, so CAT is very meaningful to reduce body injury. PPO is involved in plant photosynthesis, resistance to pests and diseases, growth, color formation, defense system and wound healing, etc. POD is involved in lignin and suberin synthesis, reactive oxygen species metabolic processes, the degradation of auxin, plant responses to external stress and plant tissue brown stain, etc.two concentrations OD600 of 0.5 and 0.1 was prepared by Ralstonia solanacearum suspension in this study.'9102'(resistant cultivar) and'Zhonghua 8'(susceptible cultivar) were cultivated to the stage of three leaves by Soil, then were injected 20μl Ralstonia solanacearum suspension under the first tiller of the main stem. They were sampled on the fifth, seventh, tenth, twelfth and fourteenth day between the first and second tiller of the main stem. PAL, CAT, PPO and POD activities and soluble protein content of every sample were measured.4 enzymatic activities were compared. Not all of the 4 enzymatic activities of resistant cultivars were higher than that of susceptible cultivars in earlier stage, but all of enzymatic activities of resistant cultivars were higher than that of susceptible cultivars in later stage.The results showed that key enzymes activity of resistant and susceptible cultivars of peanut at later stage of bacterial wilt were positive correlated to peanut disease resistance. This conclusion can be a indicator as reference of identifying peanut disease resistance.