[Objectives]This study was conducted to culture virus-free tissue culture plantlets of mid-maturing green-stalk Artemisia selengensis sp.varieties in Yangxin County.[Methods]With bud tips of A.selengensis in Yangxin a...[Objectives]This study was conducted to culture virus-free tissue culture plantlets of mid-maturing green-stalk Artemisia selengensis sp.varieties in Yangxin County.[Methods]With bud tips of A.selengensis in Yangxin as explants and MS as the basal medium,screening and proportioning of plant growth regulators were performed to establish a virus-free and rapid propagation system for mid-maturing green-stalk varieties of A.selengensis in Yangxin.[Results]The optimal callus induction medium,adventitious shoot differentiation medium,adventitious shoot elongation medium and rooting medium for explants were MS+6-BA 1.0 mg/L+NAA 0.5 mg/L+sucrose 25 g/L+agar 7 g/L,MS+6-BA 0.1 mg/L+NAA 0.1 mg/L+sucrose 25 g/L+agar 7 g/L,MS+6-BA 0.02 mg/L+NAA 0.02 mg/L+sucrose 25 g/L+agar 7 g/L and 1/2 MS+NAA 0.05 mg/L+sucrose 25 g/L+agar 7 g/L,respectively,and the seedling rate reached more than 95%.The culture conditions were as follows:temperature(25±2)℃,relative humidity 85%,illumination intensity 3000 lx,and illumination time 14 h/d.[Conclusions]This study has important practical significance for the purification and rejuvenation and large-scale industrial breeding of Yangxin A.selengensis seedlings.展开更多
Background: Viruses can cause different diseases in plants. To prevent viral infections, plants are treated with chemical compounds and antiviral agents. Chemical antiviral agents usually have narrow specificity, whic...Background: Viruses can cause different diseases in plants. To prevent viral infections, plants are treated with chemical compounds and antiviral agents. Chemical antiviral agents usually have narrow specificity, which limits their wide application. Alternative antiviral strategy is associated with the use of microbial enzymes, which are less toxic and are readily decomposed without accumulation of harmful substances. The aim of this work is to study the effect of Bacillus pumilus ribonuclease on various phytopathogenic viruses with specific focus on the ability of enzyme to eliminate them from plant explants in vitro. Materials and methods: Extracellular ribonuclease of B. pumilus is tested as an antiviral agent. To study the antiviral effect of RNase, depending on concentration and the time of application several plant-virus model systems are used. Virus detection is conducted by serological testing and RT-PCR. Results: Bacillus pumilus ribonuclease possesses antiviral activity against plant Rna-viruses RCMV (red clover mottle virus), PVX (Potato Virus X) and AMV (Alfalfa Mosaic Virus). The maximum inhibitory effect against actively replicating viruses is observed when plants are treated with the enzyme in the concentration of 100 ug/ml prior to infection. In case of local necrosis ribonuclease in the concentration of 1 ug/ml completely inhibits the development of RCMV virus on bean plants. The enzyme is able to penetrate plants and inhibit the development of viral infection, inhibiting effect for untreated surfaces decreased on average for 20%. It is also found that B. pumilus ribonuclease protects apical explants of sprouts of potato tubers from PVM and PVS viruses. Conclusion: B. pumilus ribonuclease possesses antiviral activity against plant Rna-viruses and produces viruses-free plants in the apical meristem culture.展开更多
Most epidemic models for the spread of diseases in contact networks take the assumption of the infected probability of a susceptible agent dependent on its absolute number of infectious neighbours. We introduce a new ...Most epidemic models for the spread of diseases in contact networks take the assumption of the infected probability of a susceptible agent dependent on its absolute number of infectious neighbours. We introduce a new epidemic model in which the infected probability of a susceptible agent in contact networks depends not on its degree but on its exposure level. We find that effective average infection rate ^-λ （i.e., the average number of infections produced by a single contact between infected individuals and susceptible individuals） has an epidemic threshold ^λc = 1, which is related to recovery rate, epidemic mechanisms and topology of contact network. Furthermore, we show the dominating importance of epidemic mechanisms in determining epidemic patterns and discussed the implications of our model for infection control policy.展开更多
基金Hubei Polytechnic University and Yangxin Vegetable Office School-Enterprise Technology Cooperation(KY2018-049)。
文摘[Objectives]This study was conducted to culture virus-free tissue culture plantlets of mid-maturing green-stalk Artemisia selengensis sp.varieties in Yangxin County.[Methods]With bud tips of A.selengensis in Yangxin as explants and MS as the basal medium,screening and proportioning of plant growth regulators were performed to establish a virus-free and rapid propagation system for mid-maturing green-stalk varieties of A.selengensis in Yangxin.[Results]The optimal callus induction medium,adventitious shoot differentiation medium,adventitious shoot elongation medium and rooting medium for explants were MS+6-BA 1.0 mg/L+NAA 0.5 mg/L+sucrose 25 g/L+agar 7 g/L,MS+6-BA 0.1 mg/L+NAA 0.1 mg/L+sucrose 25 g/L+agar 7 g/L,MS+6-BA 0.02 mg/L+NAA 0.02 mg/L+sucrose 25 g/L+agar 7 g/L and 1/2 MS+NAA 0.05 mg/L+sucrose 25 g/L+agar 7 g/L,respectively,and the seedling rate reached more than 95%.The culture conditions were as follows:temperature(25±2)℃,relative humidity 85%,illumination intensity 3000 lx,and illumination time 14 h/d.[Conclusions]This study has important practical significance for the purification and rejuvenation and large-scale industrial breeding of Yangxin A.selengensis seedlings.
文摘Background: Viruses can cause different diseases in plants. To prevent viral infections, plants are treated with chemical compounds and antiviral agents. Chemical antiviral agents usually have narrow specificity, which limits their wide application. Alternative antiviral strategy is associated with the use of microbial enzymes, which are less toxic and are readily decomposed without accumulation of harmful substances. The aim of this work is to study the effect of Bacillus pumilus ribonuclease on various phytopathogenic viruses with specific focus on the ability of enzyme to eliminate them from plant explants in vitro. Materials and methods: Extracellular ribonuclease of B. pumilus is tested as an antiviral agent. To study the antiviral effect of RNase, depending on concentration and the time of application several plant-virus model systems are used. Virus detection is conducted by serological testing and RT-PCR. Results: Bacillus pumilus ribonuclease possesses antiviral activity against plant Rna-viruses RCMV (red clover mottle virus), PVX (Potato Virus X) and AMV (Alfalfa Mosaic Virus). The maximum inhibitory effect against actively replicating viruses is observed when plants are treated with the enzyme in the concentration of 100 ug/ml prior to infection. In case of local necrosis ribonuclease in the concentration of 1 ug/ml completely inhibits the development of RCMV virus on bean plants. The enzyme is able to penetrate plants and inhibit the development of viral infection, inhibiting effect for untreated surfaces decreased on average for 20%. It is also found that B. pumilus ribonuclease protects apical explants of sprouts of potato tubers from PVM and PVS viruses. Conclusion: B. pumilus ribonuclease possesses antiviral activity against plant Rna-viruses and produces viruses-free plants in the apical meristem culture.
基金Supported by the Key Program Projects of the National Natural Science of China under Grant No 70431002, and the National Natural Science Foundation of China under Grant No 10372054.
文摘Most epidemic models for the spread of diseases in contact networks take the assumption of the infected probability of a susceptible agent dependent on its absolute number of infectious neighbours. We introduce a new epidemic model in which the infected probability of a susceptible agent in contact networks depends not on its degree but on its exposure level. We find that effective average infection rate ^-λ （i.e., the average number of infections produced by a single contact between infected individuals and susceptible individuals） has an epidemic threshold ^λc = 1, which is related to recovery rate, epidemic mechanisms and topology of contact network. Furthermore, we show the dominating importance of epidemic mechanisms in determining epidemic patterns and discussed the implications of our model for infection control policy.
