| Cucumber wilt is a worldwide rhizosphere soil-borne disease which caused by Fusarium pxysporium f.sp.cucumeris. It is relatively difficult to control because the high transmission speed and incidence in practical production. Environmental pollution would bring by using chemical agents for preventing the Fusarium wilt. The grafting technology can prevent Fusarium wilt effectively, but this technology was relatively difficult for the farmers because the complicated technological rules and the tedious management system after grafting, and the quality of cucumber would decline after grafting. Therefore, finding an environmental and easily operate technology for controlling cucumber wilt is an urgent problem for research workers. Recently, our research group found that parsley rotated cucumber can reduce the incidence of Fusarium wilt, and the allelopathic inhibition was found between the parsley root material extracts and the F. oxysporium under the PDA medium cultured condition. Unfortunately, the matter in the parsley root material has inhibitory effect on cucumber wilt still unclear at present.In this study,6 kinds of extract solution were obtained from the fresh parley root rhizosphere soil and seeds by using the ethanol and acetone as extraction. Extracts from parsley were examined after a repeated series of purification (four cycles) in chromatography (10mm×30cm) using a column with silicone coating. We used a bioassay involving incorporation of the various column fractions into PDA medium, and co-culture of these plates with F. oxysporum f.sp.cucumberinum. The best fractions were screened based on the effect of allelopathic inhibition (measuring the colony diameter), and various physiological and biochemical indexes of fungi were determined at the same time. To identify the composition and content of the allelochemicals in the parsley material, the allelochemicals of 24 optimal fractions in the fourth chromatography were identified by GC-MS. Then the induced resistances of 24 best fractions on the F. oxysporium were studied by using field experiment.The main results were as follows:1.24 optimal fractions were obtained form 6 kinds of parsley extract solution after a repeated series of purification (four cycles) in chromatography. Each fraction’s allelopathic inhibition effect and spores germination inhibition rate had significantly difference compared with CK in the process of every cycle chromatography. The extractions of fresh parsley root have the best allelopathic inhibition effect in three materials. Compared to the CK, the extractions of fresh parsley root have the best allelopathic inhibition effect in three materials. The allelopathic inhibition effects of the fresh parsley root acetone extractions 4th chromatography optimal fraction were 54.49,52.35%,51.55% and 50.97%, respectively, while the fresh parsley root ethylalcohol extractions 4th chromatography optimal fraction were 54.49%,54.98%, 55.62% and 55.67%, respectively.2. The biochemical metabolism of F. oxysporum was affected by the 24 best fractions significantly. The activities of three kinds of cell wall degrading enzymes (CWDEs:Cellulase.β-Glucosidase and Pectinase) and the content of fusaric acid secreted by fungi were decreased compared with CK. Cell membrane permeability increased (MDA content), but the content of soluble protein of fungi was decreased after treated with the best fractions. In addition, protective enzymes systems of fungi were affected by the best fraction of allelochemicals, the activities of SOD, POD and CAT decreased significantly after treated with the best fraction. Correlation analysis indicated that allelopathic inhibition effect had significant negative correlations with the activities of CWDEs. fusaric acid, soluble protein, SOD, POD and CAT, the correlation coefficient ranged from -0.958 to -0.812, allelopathic inhibition effect had positive correlations with MDA. And the content of MDA had negative correlations with soluble protein and the protective enzymes system.3. Many kinds of material were found in 24 best fractions by using GC-MS.13 classes and a total of 110 kinds of materials were obtained from 24 best fractions. including esters (accounted for 35%), acid (21%), amine (8%), alcohol (7%), ketene (6%) and a few of heterocyclic aromatic organic compounds. Among these 110 kinds of materials,17 kinds of materials were identified form 4 best fractions of parsley fresh root alcohol extractions; 16 kinds of materials were identified form 4 best fractions of parsley fresh root acetone extractions; 16 kinds of materials were identified form 4 best fractions of parsley rhizosphere soil alcohol extractions; 16 kinds of materials were identified form 4 best fractions of parsley rhizosphere soil acetone extractions; 20 kinds of materials identified form 4 best fractions of parsley seeds alcohol extractions:25 kinds of materials identified form 4 best fractions of parsley seeds acetone extractions. Based on the contents of allelochemicals in each best fraction, esters and acids should be the main allelochemicals in the parley extract solution. We should pay more attention to the above two kinds of substances in the process of exploit the new biological agent for preventing cucumber wilt in the future research.4. The cumber seedlings resist to the cucumber wilt was induced by all of 24 best fractions.8 best fractions of ethanol and acetone extract of parsley fresh root have the highest control effects in the 24 best fractions. Root-irrigation was the best induced method, the control effect of the 4 best factions from ethanol extract of parsley fresh root reached to 72.58%,72.25%,76.08% and 76.08%, respectively. The control effect of the 4 best factions from acetone extract of parsley fresh root reached to 72.90%, 75.92%,66.28% and 76.59%, respectively. The interval period 2d treatment had a maximum relatively control effect, and the disease index tends to stably after 7d. In addition, cucumber seedlings can significantly improve the induced resistance if twice inducing treatments have same induced concentration, the control effect of the 4 best factions from ethanol extract of parsley fresh root reached to 81.48%、85.19%、 85.19% and 86.17%, respectively. The control effect of the 4 best factions from acetone extract of parsley fresh root reached to 79.74%、73.83%、66.64% and 78.64%, respectively. The field testing confirmed that the optimal allelochemicals exist in the fresh root of parsley. |
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