| Plant viruses are hard to control, which is known as plants cancer. It was reported that every year plant viruses in the worldwide caused economic losses as much as $60 billion,and the loss of food crop alone has reached to $20 billion. To combat plant viral diseases,many efforts have been exerted to develop strategies for efficient control of them. Biological and chemical methods have great potential for this purpose. Currently, Ningnanmycin,Cytosinpeptidemycin, Dufulin, chitosan, lentinan and Ribavirin, were used to plant virus control. Lower cure rates(30–60%) and probably negative effects on environments of these antiviral agents limit their wider applications.In order to find highly efficient and environmentally friendly antiviral agents. In this study,(Ⅰ) extracts from 77 plants grown in the Qinling region were evaluated for antiviral activity against TMV. The antiviral activity of the acetone extract of cottonseed oil sludge was analyzed and the effective compounds were separated. The antiviral mechanism was also studied. Phytotoxic activity and environmental toxicology of the extract were also tested. Then we work with Shaanxi sunger road bio-science co., LTD to complete the industrialization production of extract of cottonseed oil sludge.(Ⅱ) Many microorganism were isolated from soil and plant in the Qinling region were evaluated for antiviral activity against TMV. The antiviral effective compounds were separated from bacterial strain F01.The antiviral activity of polysaccharide peptide(PSP) was tested by using half-leaf method and leaf disk method, compared with Ningnanmycin. The mechanism of antiviral activity of PSP was also studied.Our results revealed(Ⅰ) that of the 77 extracts tested, 15 plant extracts were found to exhibit potent antiviral activity with inhibition rates higher than 50% at the concentration of20 mg·mL-1. Among these, cottonseed oil sludge(87.5%), the roots of Rheum palmatum(74.8%), leaves of Ficus carica(69.6%) and barks of Cotinus coggygria(69.5%) showed higher activity at the concentration of 20 mg·mL-1. The antiviral results shows that acetone extract of cottonseed oil sludge has a 91.6% antiviral activity against TMV at the concentration of 20 mg·mL-1. Three bioactive compounds Gossypol, β-sitosterol and oleic acid were obtained from acetone extract. Antiviral effect of gossypol was higher(curativeeffect at 54.4%) than that of β-sitosterol(curative effect at 45.6%) at the concentration of 500μg·mL-1. The antiviral activity of oleic acid was 21.4%(curative effect) at the concentration of 500 μg·mL-1. Gossypol could directly affect the TMV particles, shown TMV particles were rupture and gathered up after treated with gossypol. β-sitosterol could led to increased expression levels of PR-1a and PR-5 and induce resistance responses of plants to TMV,shown increased activity of PAL and POD in tobacco leaves after treated with β-sitosterol.The phytotoxic activity and environmental toxicology experiments showed that the extract was environment friendly. Now the extract of cottonseed oil sludge has successfully achieved industrialization production as anti-plant-virus pesticides.(Ⅱ) 1100 strains of actinomycetes,670 strains of bacteria and 730 strains of fungi were isolated from soil and plant. Four strains of actinomycetes(F01, F02, F03, F04), a strain of bacteria(F05) and a strain of fungi(F06)were screened out with a moderate antiviral activity against TMV. The antiviral active component of F01 was explored as polysaccharide. The effective PSP was tested for its antiviral effect against TMV in the greenhouse. As a result, it has a stronger antiviral activity.PSP could directly affect the TMV particles, shown TMV particles were gathered up after treated with PSP. On the other hand, PSP could led to apparent oxidative burst in tobacco leaves and increased expression levels of PR-1a and PR-5. In addition, PSP could induce resistance responses of plants to TMV, shown increased activity of PAL and POD in tobacco leaves after treated with PSP. The transcriptome sequences analysis showed that PSP could regulate chitin response and increase salicylic acid, micromolecules and the protein kinase related genes expression, and to improve the disease resistance of plants. |
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