Biological Control Technology Of Tobacco Black Shank And Tobacco Black Root Rot

Tobacco is an important economic crop in China.Tobacco black shank and black root rot are caused by Phytophthora parasitica var.nicotianae and Thielaviopsis basicola,respectively.They are the most important soil borne diseases that harm tobacco.In recent years,they often occur in combination,which greatly aggravates the degree of tobacco diseases and leads to serious economic losses.In this paper,two excellent biocontrol strains,Penicillium purpurogenum Q2 and Trichoderma asperellum MX,were used to mix with amino oligosaccharide,a plant inducer,respectively.Effect on growth promoting tobacco and control efficacy of tobacco black shank and black root rot have been investigated by two biocontrol agents through the pot experiment.Results are as follows:1.Results of plate confrontation test showed that P.purpurogenum Q2 and T.asperellum MX had strong antagonistic effect on P.parasitica var.nicotianae and T.basicola,among which the inhibition percentage of Q2 on P.parasitica var.nicotianae and T.basicola was 62.86% and 80.48%,respectively.In addition,the fermentation filtrate of Q2 had strong antagonism effect.The inhibition percentage of mycelial growth,spore germination,sporangium production and zoospore germination were 61.72% and 69.14%,89.99%,85.74% and 65.12%,respectively.2.Results showed that amino oligosaccharide could not hinder the growth of the two biocontrol fungi,and could be mixed to use.Pot experiments showed that both T.asperellum MX and P.purpurogenum Q2 had better plant growth promoting effect,and the combination of T.asperellum MX and amino oligosaccharide could better promote the growth of tobacco plants,among which MX+A treatment had the best growth promoting effect.At 40 days,plant height,stem diameter,leaf length and leaf width of MX+A treatment were 48.62%,13.87%,33.01% and 22.17% higher than that of control(CK)treatment,and also significantly increased fresh weight,dry weight and root shoot ratio of tobaccoplants,which were 32.26%,52.13% and 21.15% higher than that of CK,respectively.3.Pot experiments showed that P.purpurogenum Q2 and T.asperellum MX had better control efficacy on black shank and black root rot of tobacco,and could effectively reduce incidence and disease index,and the effect was better when they were combined with aminoguanosin.Among them,control efficacy of Q2+A treatment on tobacco black shank and black root rot was 79.08% and74.88%,respectively.And the control efficacy of MX+A treantment on tobacco black shank and black root rot was 69.34% and 74.40%,respectively.4.In the field trial,control of three soil borne diseases were conducted by biocontrol fungus combined with metham-sodium fumigation.Due to the uneven distribution of pathogens under natural conditions,the incidence rate and disease control effect were somewhat different.In general,biocontrol fungus treatment had some effect on tobacco black shank,bacterial wilt and black root rot,and its growth was better than that of blank control treatment.The control efficacy of P.purpurogenum Q2 on black shank,bacterial wilt and black root rot was 70.32%,34.19% and 46.84%,respectively,and that of T.asperellum MX on black shank,bacterial wilt and black root rot was 64.30%,32.72% and 39.03%,respectively.5.When P.purpurogenum Q2 and T.asperellum MX were used in combination with aminooligosaccharide before inoculation of P.parasitica var.nicotianae and T.basicola,respectively,activities of PAL,SOD and POD in tobacco plants were effectively induced,and resistance to disease of tobacco was enhanced,and root activity and the synthesis of chlorophyllin were improved.In addition,under the stress of pathogen,the treatment of Q2 and MX with aminooligosaccharide could effectively reduce the content of malondialdehyde,thus reducing the damage degree of tobacco plants under disease stress,and could improve the content of proline in tobacco leaves,so as to improve the resistance to stress of tobacco plants,especially the combination treatment of Q2+A treatment is the most significant,followed by MX+A treatment.In general,Penicillium purpurogenum Q2 and Trichoderma asperellum MX have a strong inhibition on the growth of pathogens.The combination of aminooligosaccharide can not only promote the growth of tobacco plants,but also effectively control black shank and black root rot of tobacco,and enhance the resistance of plants,which provides a new method for the study of biological control technology of tobacco black shank and black root rot.