Effects Of Cross Protection And Induced Resistance On Cmv In Tobacco

The cucumber mosaic virus(CMV)is one of important disease attacking tobacco,but there was not efficiency controlling measure to CMV.The induced resistance of plant is that the inducting factors induce the plant to resist pathogeny microorganism.The cross protection is induced by attenuated virus to protecting the plant infected by virus.We want to discover an efficiency controlling measure to CMV by studying the induced resistance which induced by the salicylic acid(SA)and the methyl jasmonate(MeJA)to CMV in the tobacco or the cross protection which induced by attenuated virus (Fny-CMV-â–³2b)to the tobacco.The 2b gene of CMV is able to promote the cell-to-cell movement,the long-distance movement and the systemic movement spread of cucumber mosaic virus in infected plant, and to suppress post-transcriptional gene silencing or the salicylic acid-mediated defense response.A mutant of CMV lacking 2b gene(Fny-CMV-â–³2b)was constructed to study the cross protection in the tobacco.Results showed that mild mosaic symptom appeared in tobacco infected by the Fny-CMV-â–³2b and the chenopodium amaranticolor inoculated by the Fny-CMV-â–³2b appeared milder necrosis spot than that represented in the plant infected by the CMV,this suggested that the Fny-CMV-â–³2b was an attenuated virus.The Fny-CMV-â–³2b can enhance plant height and leaf area in the infected plant,increase 15.49%and 18.26%,respectively,and also enhance fresh and dry weight of leaves,stems, roots and the whole plant of the infected plant,this suggested that the Fny-CMV-â–³2b advanced the growth of the infected plant and remarkably increased the biological output of the infected plant.The content of total chlorophyll,chlorophyll-a,and chlorophyll-b remarkably reduced in the plant infected by Fny-CMV,but The content of total chlorophyll, chlorophyll-a,and chlorophyll-b had not change the plant infected by Fny-CMV-â–³2b.the infection of Fny-CMV-â–³2b influence slightly the net photosynthetic rate(Pn),transpiration rate(E),stomatal conductance(Gs),and intercellular CO2 concentration(Ci)of the infected plant,and do not influence the Fm,Fv/Fm,Yield,qP,NPQ and ETR of the infected plant. These results suggested that the Fny-CMV-â–³2b didn't destroy the photosynthetic tissue and influence the photosynthesis in infected plant.The SA could induce the fastness to the virus,epiphyte and bacteria in a number of plant,have an important role in the systemic acquired resistance in plant,and is one of signal molecule that induce the systemic acquired resistance.The MeJA which is an important phytohormone have broad physiological function and could induce the systemic acquired resistance in plant.The spraying leaves with SA and MeJA in two phases of the tobacco in order to study the virus resistance induced by SA and MeJA in tobacco.The results of research show that the spraying leaves with SA and MeJA can induce tobacco fastness to CMV,disease index fall from 60 to 40,effects of fastness to CMV were 31.69% and 33.89%.The spraying leaves with SA and MeJA can increase activity of SOD in tobacco leaves,to compare to comparison,increasing 273.56%and 349.16%.The spraying leaves with SA and MeJA can increase activity of POD in tobacco leaves,to compare to comparison,increasing 40.71%and 42.17%.After inoculating CMV,activities of POD in spraying leaves with SA and MeJA were 12.99%and 35.70%greater than comparison.The spraying leaves with SA and MeJA can increase the content of H2O2,to compare to comparison,increasing 147.62%and 220.00%.After inoculating CMV,the content of H₂O₂ in spraying leaves with SA and MeJA increase 155.98%and 170.55%.The spraying leaves with SA and MeJA can depress activity of POD in tobacco leaves,to compare to comparison,falling 43.94%and 49.76%.These show that SA and MeJA can improve the content of H2O2 of secondary messenger SAR,induce SAR to improve the fastness to CMV through increasing activity of POD and SOD,falling activity of CAT.In a word,CMV with absenting 2b,can promote healthy development of tobacco and no affect photosynthesis,chlorphyll fluorescent properties of tobacco leaves.The spraying leaves with SA and MeJA can increase activity of POD,SOD and the content of H₂O₂,fall activity of CAT,induce tobacco resistance to CMV.