Effects of three compounds from Comastoma pedunlulatum（Royle ex D. Don） Holub on the resistance to tobacco mosaic virus and activities of four defense enzymes in tobacco

【Objective】To evaluate the anti-tobacco mosaic virus(TMV) activity of three compounds isolated from Comastoma pedunlulatum(Royle ex D. Don) Holub and their effects on the activity of four tobacco defense enzymes, which could provide lead compounds and theoretical basis for the research and development of effective control of TMV plant pesticides. 【Method】Nicotiana glutinosa was used as the materials, there were three groups, which were compounds treatment group(swertisin, comtraide A and isoorientin), negative control(CK) and positive control(8% ningnanmycin). The protective and inactivation effects of the compounds on TMV infection were determined by half-leaf method. Using tobacco cultivar K326 as the materials, control groupnegative control(CK) and TMV-inoculated control(CK+TMV), ningnanmycin treatment group positive control(PC) and swertisin, comtraide A and isoorientin treatment were set. The activities of polyphenol oxidase(PPO), phenylalanine ammonlyase(PAL), superoxide dismutase(SOD) and peroxidase(POD) in tobacco leaves were determined by defense enzyme detection kit. 【Result】Swertisin, comtraide A and isoorientin could reduce the lesion numbers of TMV on N. glutinosa plants when the tobacco leaves were first applied with compounds at 100 μg/mL and then inoculated with TMV, showing good protective effects against TMV infection, with the inhibition rates of 50.05%, 57.55% and 61.73%, respectively, whereas the inhibition rate of ningnanmicin against TMV was only 47.75%. When the TMV were mixed with compounds and then inoculated the plant leaves, swertisin and comtraide A also had good inactivation effects against TMV, whose inhibition rates were 51.65% and 45.66%, respectively. After application of swertisin, comtraide A and isoorientin, the maximum activities of defense enzymes PPO were reached after 24, 12 and 24 h, respectively; the maximum activities of PAL were reached after 72 h; the maximum activities of defense enzymes POD were reached after 24, 48 and 72 h, respectively. The activities of PPO, PAL and POD were significantly different from those of CK at the maximum value(P<0.05), while the activities of SOD were not significantly different from those of CK group(P>0.05). 【Conclusion】Swertisin, comtraide A and isoorientin extracted from C. pedunlulatum show good protective activity against TMV when the concentration is 100 μg/mL, and they have the potential as biological pesticides or lead compounds against TMV.