At present, although studies on the antibacterial activity of plant extracts against plant pathogens are much less than the studies on insecticidal activity, plants are still considered to be the best development resources for chemical synthetic fungicide substitutes.
Botanical fungicides use certain antibacterial substances contained in some plants or induced plant defensins to kill or effectively inhibit the growth and development of certain pathogenic bacteria. Antibacterial compounds in plants are a variety of secondary metabolites produced by plants with antibacterial activity, including many different types of alkaloids, flavonoids, proteins, organic acids and phenolic compounds, such as artemisia Capillin, Saponin. It has been reported that 1389 plants may be used as fungicides.
Plant defensins refer to compounds synthesized by plants and accumulated in plants after infestation by pathogenic microorganisms, such as Pterocarpans extracted from Erythrina crista Galli L., which are plants. The response of the body. The original Pulsatilla extract has a higher inhibition rate against the hyphae of the wheat gibberella, which not only inhibits the expansion of the hyphae, but also causes the mycelium on the pathogen to atrophy. The 91502-5 preparation is processed from the original pulsatilla extract, and its field The test results show that the preparation has better control effect and obvious yield increasing effect. Coptis contains a large amount of alkaloids. In addition to inhibiting the mycelial growth and spore germination of many pathogenic fungi, these alkaloids also have a strong inhibitory effect on Xanthomonas oryzae pv.
Botanical germicidal substances are widely found in nature and are an important source of ideal fungicides. Four compounds were isolated from the Phyllostachys pubescens, in which compound II (lα, 2α, 4β, 6β, 8α, 9β, 13-heptahydro-dihydrofurfurfuran) has bactericidal activity against Zea mays The inhibitory virulence of spore germination was 169.29 mg/L. The volatile oil extracted from Ephedra and Asarum has a strong inhibitory effect on plant pathogenic bacteria. The crude extract of Magnolia officinalis has a strong inhibitory effect on a variety of phytopathogenic fungi, and has a high control effect in pot and field experiments.
Ginkgo biloba extract has certain control effects on various fruit tree diseases. Taking the chemical structure of bioactive substance B in Ginkgo biloba as template, Laiyang Agricultural College Bionics Center successfully synthesized the ginkgo bactericide, the green pedicle, which has significant antibacterial and bactericidal effects on various pathogenic bacteria. The results showed that bamboo extracts such as Maojinzhu, Phyllostachys pubescens, C. chinensis, and T. chinensis showed strong antifungal effects, and the hyphal inhibition rate of S. cerevisiae was above 80%. Screening of antibacterial activity against 56 plants showed that many plants such as lettuce, Xanthium and Sophora alopecures have strong antibacterial activity. Studies on the antibacterial activity of Sophora flavescens extract showed that the ethyl acetate extract of Sophora flavescens had significant inhibitory effects on various fungi and bacteria, and the diameter of the inhibition zone was 10~42.nm. In recent years, the emulsion prepared by Hunan Cang seed oil has good control effect on the main diseases of tea tree, such as tea red rust, smut, tea cloud blight, cotton wilt and verticillium. The pulverized material such as mint is treated with soil with a weight of 0.5% to 0.1% to effectively infect the soil of cotton wilt, and the control effect is 43.9%~74.3%. Extracts of plants such as tobacco, tea cake, fish vine, and tripterygium wilfordii can inhibit the germination and growth of certain pathogen spores, or prevent pathogens from invading plants. In addition, many plants have been found to have strong antibacterial activity, such as tea, pepper, some mangroves, and mosses.
Plant-derived antiviral agent. Plant viruses are known as "plant cancers". About 1,000 species are known at present, which are highly harmful in agriculture, and their degree of harm is second only to fungal diseases. According to statistics, the annual damage caused by plant virus diseases in the world exceeds 15 billion US dollars. Since plant viruses mostly have absolute endoparasites and systemic infestation, it is difficult to control plant virus diseases.
The extracts from two plants, Chenopodium serotinum and Hosta plantainea, were selected from 90 plants to have a certain therapeutic effect on tomato mosaic virus disease; the extracts of Forsythia suspensa, Rhubarb and Radix Isatidis had TMV Stable efficacy; rhubarb extract not only affects the content of TOMV (tomato mosaic virus) in tomato plants, but also affects its symptoms. The purple rind extract has a significant inhibitory effect on plant viruses. According to the research, the compounding agent MH11-4 prepared from several plant extracts such as Shanglu, Licorice and Forsythia has a good control effect on plant viruses. Although plant extracts have certain control effects on plant viruses, their composition is complicated, and the mechanism of action is restricted by environmental influences. In actual production and application, stability is often poor. Therefore, in order to develop safe and effective antiviral agents from plants, it is necessary to conduct in-depth research on antiviral active substances in plant extracts and their antiviral mechanism.
Some plants are both anti-fungal and anti-bacterial, nematicidal and other pests. It can be seen that plant-derived fungicides have a broad spectrum of targets. Nematocidal plant sources include garlic (Allium sativum L.), Andrographis paniculata Ness, Azadirachta indica Adr. Juss, Hedera helix L., Nicotiana tabacum L., and the like. Antibacterial plant sources include garlic (Allium sativum L), Andrographis paniculata Ness, Fineleaf schizonepeta, Onium cepa.L., Agrimonia pilosa Ledeb.., and Scutellaria barbata L. Scutel-larua barbata D.) et al.
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