| Plant root-knot nematodes are an economically important soil-borne pathogens,which inhabit in soil diffusely,have many kinds of host plants and can result in poor crop performance. Those have hitherto been controlled mainly by chemical nematicides,but with an increase in general awareness of the harmful effects of chemical ones and the changing public attitude towards environmental pollution,several effective nematicides are losing their popularity among farmers for protecting crops from nematode infestations. It has now become essential to search for alternative and environmentally friendly ways for the management of root-knot nematodes in various agricultural crops.Plant appears to be a factory of nature chemical and bio-active materials, which can product various preventive and protective compounds to protect itself from damage of pest and intrusion of pathogens. The compounds from plant may come to be regarded as an inexhaustible source of harmless pesticides having low plant and human toxicity and being easily biodegradable. It is urgent for people to develop modern pesticides that are harmonious with environment, however, screening and isolating active component from plant conforms to the demand. To this day, application of plants in killing root-knot nematode was relatively slow, so it is urgent to exploit and apply high-effective nematicidal plants against root-knot nematode. Based on the ideas mentioned above, several issues were investigated in the thesis listed as following:1. Root-knot nematodes species from field protected cultivation vegetable in Henan province were investigated with the method of morphology and identification host, The investigation indicated that M. incognita was widely distributed which was the dominant species, its populations were found in 100% samples. This indicated M. incognita was the dominant species under protected cultivation vegetable field in Henan province and provided theoretic basis.2. Biological activity against M. incognita of 18 plants, which were Cultivators or wild Plants that were not or slightly damaged by root-knot nematodes and of pesticidal Traditional Chinese Herb, was screened and validated. The results showed that biological activity of B.B was highest in the selected plants, nematicidal effect of which on J2 was lower slightly that of soybean hull, and inhibition rate on eggs hatch of which was above 50% and highest in selected plants. The biological active ingredients of B.B were further traced by liquid-liquid extraction, column chromatography separation and TLC detection, three active ingredients were grained. The chemical structures of them were detected by NMR, GC-MS and LC-MS, the results indicated that all of them were alkaloid compounds, respectively A, B, C. The revised mortality J2 was 59.67%, 52.63% and 41.87% respectively in 72 h of their treatment, and the inhibitive rate was 73.43%, 59.23% and 52.86% respectively in 72 d of their treatment. This can provide theoretic basis for artificial pesticide of natural plant analogs.3. The nematicidal mechanism of three active ingredients was studied form physiological metabolism of M. incognita and enzyme concerning metabolism. The result showed that the nematicidal components are likely to inhibit GST and CAT activity, destroy the balance of oxidation and anti-oxidation by affecting the oxide metabolism, affect cell function and in the end result in death of J2. In addition, the stratum corneum on body surface of M. incognita was damaged, resulting in penetration of body inclusions, this was possibly other reason that nematode was killed by three active ingredients. Considering synthetically the toxicity of them to M. incognita, the toxic effect compound A was higher than the others. The toxicity of B.B. and synergistic effect of three active ingredients were proved from nematode toxicology, this will be helpful for development and application of active ingredients from B.B..4. The advanced extracting apparatus was designed and validated,and the extraction parameters were optimized with response surface methodology. The results indicated that the apparatus was apt to extract alkaloid from B.B., the yield of total alkaloid was 8.47 mg·g-1 and higher than that of others selected methods, recovery of solvent could be up to 87.67%. The conditions of 57.7℃, 75.2% ethanol and heating and refluxing for 13.2 h were optimium, and the yield of total alkaloid could be up to 9.63mg/g, which was in consistent with the theoretic value. So the extraction parameters were credible and had some practical value. This provided theoretical parameters for its exploit in agriculture, medicament, food and so on.5. The powder and extraction of B.B. root were directly processed into WP and EC, and physical and chemical examination, biological assay indoor and efficacy test of them were carried out. The results showed that the optimum recipe of EC was as followed: extract(20%)+a(50%)+b(10%)+c(5%)+d (10%)+e (5%), LC50 of it to J2 and eggs were 2118.43 mg/L and 2090.18 mg/L respectively. The optimum recipe of WP was as followed: powder(77.5%)+a(2%)+b(2.5%)+c(2%)+d(4%)+e(12%), LC50 of it to J2 and eggs were 2113.43 mg/L and 1799.98 mg/L respectively. The results of pot and field experiments indicated that control effect of EC and WP, diluted below 400 times, was above 60%, and both of them could accelerate growth of tomato. In the same diluted times, the control effect of WP was slightly higher than that of EC. This provided theoretical basis for commercialization of plant nematicide. |
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