The Mechanisms Of Continuous Cropping Obstacle Formation Of Chilli Pepper And The Response Of Chilli Pepper To Continuously Mono-cropped System

Chilli Pepper is one of the most popular vegetables.Due to long-term large-scale monoculture planting,continuous cropping obstacles occurs frequently,which seriously restricts the development of pepper industry.Previous studies have shown that the main causes of continuous cropping obstacles mainly focus on accumulation of autotoxic substances,imbalance of soil microbiome and soil nutrients.However,the main causes of continuous cropping obstacles of chilli pepper are still unclear.Therefore,the pot experiment was carried out to study the responses of chilli pepper to continuous cropping obstacles in continuously mono-cropped system in Jize County,Handan City,which is a national characteristic agricultural product advantage area of pepper and have been planted chilli pepper for decade years.Moreover,the soil barrier caused by pepper continuous cropping was studied from the characteristics of soil microbial community,soil enzyme activity and root exudates through soil pot experiments and hydroponics experiments.The main results are as follows:(1)Clarified the response of chilli pepper in a continuously mono-cropped systemThe pot experiment was conducted to study,the response of Hangjiao 8(HJ 8)andHangjiao 5(HJ 5)to continuous cropping obstacles in continuous cropping and noncontinuous cropping(control)soil.The results showed that the health index of plant seedling stage of HJ 8 and HJ 5 in continuous cropping soil was 45.81%and 40.71%lower than that of the control.Continuous cropping obstacles significantly inhibited the growth of pepper,and the inhibition effect on plant height and dry weight of HJ 8 was stronger than that of HJ 5.The activities of POD and SOD in leaves of HJ 8 in continuous soil were 40.75%and 32.21%lower than that in the control,respectively.HJ 5 could regulate the activity of SOD and resist adversity stress.The content of p-Hydroxybenzoic acid,Syringic acid and Ferulic acid in continuous cropping soil was 22.01%、46.91%and 71.81%lower than that in control.Continuous cropping obstacle significantly reduced the activities of Sucrase and Acid Phosphatase enzyme in the soil with HJ 8.Continuous cropping obstacle reduced the richness of soil bacteria.In continuous cropping soil,antagonistic bacteria,Bacillus and Rhodobacteria were 43.96%and 31.42%lower than control,and the abundance of pathogenic fungi,Ampullaria was 44.84 times higher than the control.(2)Clarified the main components of autotoxicant in pepper root exudatesThe components of root exudates of pepper in seedling and flowering stages were determined using hydroponic experiment.There were 11 kinds of root exudates detected in seedling stage and 14 kinds of roots exduates detected in flowering stage.The common root exudates in the two periods included Palmitic acid,Stearic acid,Sinnamic acid,4Hydroxybenzoic acid,Lactate,Succinic acid,Diisobutyl phthalate,Dioctyl phthalate,Dfructose,D-arabinose,β-Taropyrans.The root exudates in flowering stage were more than 6 species in seedling stage,which were Ethylamine,Succinic acid,4-Hydroxybenzoic acid,Squalene,D-arabinose and Dioctyl phthalate.The phenolic acids exudated by root were Gallic acid,p-Hydroxybenzoic acid,Phthalate,Clove acid,Ferulic acid,Cinnamic acid and Coumarinic acid.The contents of Gallic acid,Goumarinic acid,Phthalate,Ferulic acid and Cinnamic acid in root exudates at flowering stage was 3.71 times,2.22 times,9.59 times,4.44 times and 3.73 times of seedling stage.The main phytotoxic exudated by the root system of pepper are Diisobutyl phthalate,dioctyl phthalate,phthalic acid,syringic acid,phydroxybenzoic acid,gallic acid,cinnamic acid,ferulic acid,coumaric acid,The amount of Syringic acid and p-Hydroxybenzoic acid in seedling stage was higher than that in flowering stage,the amount of Phthalic acid,Gallic acid,Cinnamic acid,Ferulic acid and Coumaric acid in flowering stage was higher than that in seedling stage.(3)Explored the main causes of soil barrier in Pepper continuous cropping systemExtracts of continuous cropping soil for non-sterilization(S1),sterilization(S2),and then continuously poured into the sterile CK soil-pepper system to explore the main factors causing continuous cropping obstacles of pepper through the separation of soil phenolic acids and microorganisms,.The results showed that S2 significantly reduced the plant height and leaf number by 13.63%and 26.24%respectively compared with CK.For the S1 treatment,the soil invertase activity increased by 76.01%,reduced the contents of phydroxybenzoic acid and Syringic acid by 12.73%and 5.62%,increased the abundances of Sphingomonas and Rhodobacteria compared with S2 treatment.Fusarium and Alternaria were enriched in S2.Based on the function prediction of fungi,it was found that the addition of continuous cropping soil extracts could transform the vegetative type of fungi into the pathological type.The change of soil microbial community caused by long-term continuous cropping of chilli pepper led to continuous cropping obstacles.In conclusion,the composition and structure of soil fungi and bacterial communities have been significantly changed due to the long-term single continuous cropping of pepper and the accumulation of root autotoxins,which makes the antagonistic bacteria abundance decrease,the pathogen enrichment,and the soil enzyme activity decreases,caused the soil nutrient circulation ability becomes poor,the plant antioxidant enzyme system is disordered,and monoculture obstacle.