Allelopathic Effect And Biological Regulation Of Phenolic Acids In The Continuous Cropping Strawberry Soil

Phenolic compounds have been implicated as allelochemicals in many types of plants under mono-cropping management systems. In order to explore the role of phenolics in strawberry continuous cropping obstacle, we firstly identified the species and monitored the changes in phenolic acids from rhizosphere soil at different developmental stages of a mono-cropping strawberry system, topsoil and the decomposition of stem and leaf; Secondly, we assessed the effects of different types and concentrations of phenolic acids that had been exogenously added in vitro to Fusarium oxysporum f. sp. Jragariae and Colletotrichum gloeosporioides and tested and verified the relationship between the occurrence of strawberry anthracnose crown rot and the changes in root structure in response to different phenolic acids at varying concentrations using pot expermrnts; Finally, we studied the soil sterilization, applying different fertilizer, different crop residue decomposition, different kinds of earthworm on the regulation of soil phenolic acids and strawberry anthracnose crown rot. During the period, we also studied the soil sterilization and applying different fertilizer on the influence and regulation of strawberry plant growth and the effects of soil enzyme activities. The purpose of our studies is to provide theoretical basis and technical guidance for strawberry continuous cropping obstacle integrated biological control. Main results are as follows:Ten phenolic compounds were identified from rhizosphere soil of strawberry plants by HPLC. Compounds detected from soil samples in order of their appearance in the eluant:gallic acid, protocatechuic acid, chlorogenic acid,p-hydroxybenzoic acid, caffeic acid, syringic acid, vanillin, p-coumaric acid, ferulic acid and trans-cinnamic acid.The concentrations of ferulic acid (FA) and p-coumaric acid (PA) were higher compared to other phenolic acids. The total phenolic content and the phenolic acid content of PA and p-hydroxybenzoic acid in rhizosphere soil increased with the development of the strawberry plant, In contrast, caffeic acid, syringic acid, vanillin, and trans-cinnamic acid maintained relatively stable levels, whereas the concentrations of FA, gallic acid, protocatechuic acid, and chlorogenic acid decreased.Our research found that different kinds and concentrations of exogenous phenolic acids had different effects on colony growth and and conidial germination of F. oxysporum f. sp. fragariae. The effects of phenolic acids were found to be concentration-dependent and low concentrations of phenolic acids are generally believed to boost, but high concentrations can inhibit, promote or have no effect on colony growth and and conidial germination of F. oxysporum f. sp. fragariae. Amendments of FA at the concentration detected at the seeding stage in the rhizophere soil enhanced conidial germination and the colony growth of F. oxysporum f. sp. fragariae. Gallic acid acted synergistically with FA to increase conidial germination. Amendments of PA at the concentration detected in the rhizophere soil showed inhibitory effects on conidial germination, but stimulatory effects on the colony growth of F. oxysporum f. sp. fragariae, and protocatechuic acid and p-hydroxybenzoic acid acted synergistically to promote this effect. At relatively low concentrations, trans-cinnamic acid and benzoic acid had strong inhibitory effects on spore germination, while caffeic acid, syringic acid, vanillin, and chlorogenic acid had neutral effects. Overall, our results suggest that relatively high concentrations of FA might account for the early infection of strawberry seedlings with Fusarium wilt. The concentrations of PA and FA were relative higher than other phenolic acids in the plow layer soil of strawberry fields and decomposition of strawberry stem and leaf, which differed in their influence on the growth of C. gloeosporioides and development of strawberry anthracnose crown rot symptoms. Our results suggest that relatively high concentrations of PA and FA may increase the occurrence of strawberry seedling anthracnose crown rot. The effects of phenolic acids were found to be concentration-dependent, and strawberry anthracnose symptoms were apparent before affecting root growth of the strawberry plant. We could control the occurrence of strawberry anthracnose crown rot by regulating the trans-cinnamic acid (TA) content in plow layer soil.Our research showed that root architecture and ratio of root weight to leaf weight of strawberry plants had a different change in different growth and development stages for soil sterilization and normal soil. The growth of strawberry plants root were inhibited by soil sterilization compared with the normal soil cultivation of strawberry plant. The treatments of soil sterilization or applying organic fertilizer could significantly (P<0.05) promote phenolic acids content increasing in rhizosphere soil of strawberry plant compared with unsterilized soil and applying inorganic fertilizer, and the increasing of phenolic acid applied with vermicompost was significantly (P<0.05) lower than that applied with cattle manure. After soil sterilization, the activity of soil polyphenol oxidase could be recovered if applying organic fertilizer. The activity of soil catalase could be faster recovered if applying organic fertilizer than inorganic fertilizer. Applying vermicompost could significantly(P<0.05) promote the activity of soil urease compared with applying cattle manure or inorganic fertilizer. The activity of soil sucrase decreased significantly (P<0.05) because of soil sterilization and there are no significant difference between treatments of applying different fertilizers.The results showed that under the condition of high concentration spore, the decomposition of sorghum stem and leaf could decrease the disease index (DI) of petiole and the infection degree of crown longitudinal section (IDC)67.42%and91.00%compared with CK while under the condition of low concentration spore, the decomposition of sorghum stem and leaf could inhibit the growth of root compared with CK. That the content of p-coumaric acid was relatively high in decomposition of sorghum stem and leaf may be the reason for inhibition of strawberry anthracnosis.Earthworms can decrease the concentration of phenolic acids which produced by strawberry stem leaf and root residue decomposing in continuous cropping soil. The degradation effects of different kinds of earthworm on residue decomposition were different.