Study On The Nutritional Effect And Bacterial Suppression Mechanism Of Digested Pig Slurry Applied To Tomato Substrate Cultivation In Facilities

Anaerobic digestion is one of the main technologies for livestock manure resourcing,but the problem of application of anaerobic fermentation solution must be solved,otherwise it will lead to serious secondary pollution.Digested slurry is rich in nutrients such as nitrogen,phosphorus and potassium,and is widely used in crops production,but the use of digested slurry requires sufficient farmland around the livestock farm.The application of digested slurry to substrate cultivation in facilities can provide a new way to solve the problem.Here,tomatoes were used as subjects,Two-Factor experimental design of fertilizers（digested pig slurry and mineral fertilizer）and soilless substrates（peat and cinder）was used.To study the nutritional effects of digested pig slurry in the"substrate-plant"system and its mechanism of increasing yield and improving quality,and to investigate the mechanism of digested slurry suppression of tomato soil-borne wilt pathogen（Ralstonia.Solanacearum RS）.The main results are as follows:1.Digested slurry application into peat substrate increased the leaf photosynthetic rate,and the total nitrogen and total phosphorus of plants were higher than mineral fertilizer application into peat substrate by 31.9%and 58.0%,respectively.Compared to mineral fertilizer treatments,digested slurry treatments significantly increased the p H,organic matter and available phosphorus content of substrates（P<0.05）.The results of PCA showed that the best performance of plants was achieved in digested slurry application into peat substrate,and the plants in mineral fertilizer application into cinder substrate treatment performed the worst.Both digested slurry and mineral fertilizer treatments showed significant disease symptoms on tomato leaves after inoculation with RS.However,the disease incidence of digested slurry treatment was decreased by 60.6%compared to mineral fertilizer treatment,and RS population in substrate and caudex tissue were significantly lower than mineral fertilizer treatment（P<0.05）.Oxidative stress parameters（hydrogen peroxide,superoxide anion production rate and malondialdehyde content）of tomato plants in mineral fertilizer treatment were significantly higher than digested slurry treatment（P<0.05）.Meanwhile,the antioxidant enzymes（superoxide dismutase,peroxidase and ascorbate peroxidase）and defense enzymes（polyphenol oxidase）activities of tomato plants in mineral fertilizer treatment were significantly lower than those of digested slurry treatment（P<0.05）.It was shown that digested slurry treatment reduced the incidence of tomato wilt disease,and reduced oxidative stress and membrane damage caused by RS bacteria by increasing plant antioxidant enzymes and defense enzymes activities.2.The highest fruit yield of tomato was obtained in digested slurry application into peat substrate treatment with 6.004±0.3 kg·m^-2,while the yield of digested slurry application into peat substrate treatment was not significant compared to mineral fertilizer application into peat substrate treatment.Digested slurry application into peat substrate treatment significantly increased the leaf photosynthetic efficiency and carbohydrate contents（sucrose,glucose and fructose）compared to other treatments,as well as the activities of sucrose phosphate synthase and AGPase in leaves（P<0.05）.The soluble sugar content in digested slurry treatments were significantly higher than mineral fertilizer treatments（P<0.05）.In addition,the acid invertase activity of fruit in digested slurry application in peat substrate treatment was increased by 36.3%,31.3%and 42.2%,respectively,compared to mineral fertilizer application into peat substrate,digested slurry application into cinder substrate and mineral fertilizer application into cinder substrate,while the AGPase activity was decreased by 24.2%,16.0%and 36.4%,respectively.Digested pig slurry application into peat substrate treatment regulated the activities of carbohydrate metabolism enzymes of plants,and obtained the better yield and quality.3.Transcriptome data analysis showed that the expression levels of differentially-expressed genes（DEGs）involved in oxidation resistance,cell wall reinforcement were upregulated in digested slurry+RS treatment,while pathogen-associated molecular pattern-triggered immunity（PTI）and effector-triggered immunity（ETI）were partly upregulated.Multiple hormone-related genes were differentially expressed in digested slurry treated plants.After inoculated with RS,the highest jasmonic acid（JA）content was found in digested slurry treated plants,while the highest ethylene（ET）content was found in mineral fertilizer treated plants.Digested slurry induced resistance to RS in tomato plants,and this resistance was associated with activated PTI and ETI-related responses and enhanced disease resistance and tolerance via several hormone signaling pathways（e.g.,SA,JA,ET,and ABA）.