Study Of Biological Control Against Potato Virus Y Disease For Tobacco

Potato virus Y disease for tobacco is a devastating disease caused by Potato virus Y(PVY), transmitted by Myzus persicae(Sulzer). PVY can cause some symptoms(mosaic, deformity, dwarf, peeling) and influence the yield and quality of tobacco seriously by causing veins necrosis in tobacco leaves. In recent years, as global warming and aphid outbreak, the disease rapidly spreaded of the disease in Shaanxi province, and became one of the most important diseases on tobacco production. Currently, the disease prevention and control measures mainly dependent on breeding for disease resistance and chemical control. But the results are not satisfactory, along with the more and more attention paid on pesticide residues, the biological control has become a hot research area in control of the PVY disease.Combined with the research of protein elicitor in other bacillus reported by relevant researchers, Bacillus amyloliquefaciens Ba-168 screened by the lab showed significant disease-suppressive efficacy against PVY disease for tobacco in greenhouse. Basing on the bio-activity assay and hypersensitive response test, the laboratory found that the Bacillus amyloliquefaciens Ba-168 can secrete a kind of hypersensitive protein which can induce the plant acquire induced systemic resistance. Many methods have been used to get coarse separation of the Hypersensitive protein, such as strain fermentation,ultrafiltration membrane,ammonium sulfate precipitation. Direct detection of antimicrobial activity on SDS-PAGE and Sol-gel bio-active test suggested molecular mass of the protein about 25 kDa.By using N.tabacum var. Samsun NN and Nicotiana tabacum as materials respectively, this report analyzed the resistance induction of BaPE1 on tobacco by means of half leaf method, the esistance induction improved with the increase of concentration. The experiments demonstrated that BaPE1 could induce defence substances in tobacco and BaPE1 had significant effects on prevention and treatment of PVY, the protective effect of spraying BaPE1 48 hours before PVY inoculation could reach up to 70.46% and the treatment effect of 24 hours after inoculation up to 61.30% on tobacco, and all the effects are significantly higher than the control groups. Meanwhile, the experiments detected the disease-resistant enzyme activity of SOD, POD and PAL on tobacco of BaPE1. After treated with BaPE1, the activities of SOD, POD and PAL were increased in tobacco leaves. Among which, the activities of SOD and PAL reached peak at the 7th day after BaPE1 treatment, respectively which were 3.0 times and 3.9 times higher than the untreated check; and the activity of POD reached peak at the 9th day after treatment, increased 1.7 times compared with control group. The experiments in the field indicated that plant height, stem girth and area of maximum leaf of tobacco were all highest in four groups.These results indicated that BaPE1 is a kind of plant immunizing agent and has a strong inhibitory action to PVY, and could increase obviously disease-resistant enzyme activity. So BaPE1 have a good development and application prospects.As one primarily parasitical natural enemy to Myzus persicae(Sulzer), Aphidius gifuensis is typical representative of the natural enemy biological control. A large number of naturally occurring in the field not only can control the quantity of Myzus persicae, but also reduce the incidence of tobacco virus disease. This paper mainly aims on the occurrence dynamics of the key tobacco pest insects in Hanzhong, and the control effect of Aphidius gifuensis and “highly active low toxic” pesticide on Myzus persicae, to meet the requirement of IPM in Hanzhong tobacco fields. The results indicated that the population dynamics of Myzus persicae in Hanzhong tobacco fields appeared as double peak curve, with first peak period in late May or early June and second peak period in middle until late July. With time increasing,the population of Myzus persicae delined. The research on the times of releasing Aphidius gifuensis control aphids has showed that: the successive releasing Aphidius gifuensis can control the growth rate of aphid effectively. The survey indicate that the control effect of raleasing Aphidius gifuensis is significant, equal to use agricultural chemicals in the field. It is significant useful to decrease the aphid’s harm and PVY disease to tobacco in the field by the methlod of releasing Aphidius gifuensis freely and using “highly active low toxic” pesticide.