| At present,many apple orchards in China are still dominated by apple with standard rootstock which planted in 1980 s and 1990 s.Modern cultivation system characterized by labor-saving and intensive cultivation needs to be established urgently.However,due to the restriction of land resources,cultivation conditions and regional development,continuous cropping obstacles were inevitable in many orchards.Based on the previous research,this study explored to establish an environment-friendly prevention and control system for continuous cropping obstacles.Firstly,the fungal inhibition effects of three plant materials were studied.And then the fungal inhibition effects of Tagetes erecta were analyzed.The effects of T.erecta biofumigation on the growth and soil environment of continuous cropping in potted and field cultivation conditions were studied.Finally the volatile components of T.erecta and the fungal inhibition effects of two main components purifiers were determined,which provide theoretical basis and technical support for overcoming the apple replant disease.The main findings were as follows:1.The fungal inhibition effects of the volatile components(40℃)of Allium fistulosum,Brassica juncea and T.erecta were significantly different.At the same concentration,the mycelium growth of four species of F.oxysporum,F.fusobacterium,F.solani and F.moniliforme were inhibited differently,the inhibition rate of Brassica juncea and T.erecta were 98.47 %-100 % and 99.24 %-100 % respectively,but the inhibition rate of A.fistulosum was only 0.69 %-4.65 %.2.The volatile components of T.erecta air-dried powder had strong inhibitory effects on the mycelium growth and spore germination of four species of Fusarium.The inhibition rate of mycelium growth from 1.67 to 33.30 g/L was 20 %-100 %,and the inhibition rate against spore germination was 8.26 %-90.08 %.The inhibitory effect increased with the increase of T.erecta dosage.The fungal inhibition effect of the flowers collected before the frost was the best,the inhibition rate was 100 %,which was obviously better than that of the stems and leaves;the fungal inhibition effect of stems and leaves collected after the frost was the best,and the inhibition rate was 96.33 %-100 %,which was obviously better than flowers.The inhibition rates of T.erecta plant extract(20-100 g/L)on the growth of four species of Fusarium were 6.55 %-81.89 %,and the inhibition was enhanced with the increase of concentration.The volatile constituents of T.erecta changed the mycelium morphology of F.solani,which made the mycelium thinner,and the short and thin branches increased,the mycelium grew in a mess and some mycelium were break directly,the surface of themycelium was broken and the material inside overflowed.3.Adding T.erecta air-dried powder,fresh plants and fresh plant extracts to apple replanted soil,T.erecta powder treatment had the best effects on alleviating apple replant disease.Compared with the control,the plant height,ground diameter,the fresh and dry weight in shoot and root of Malus hupehensis Rehd.seedlings increased by 107.7 %,87.3 %,192.0 %,194.1 %,196.5 %,and 117.6 % respectively.The net photosynthetic rate of leaves increased by 32.6 %.The root length,root surface area,root volume and root tip number were1.9 times,1.8 times,1.8 times and 2.0 times,respectively,and the root respiration rate increased by 64.6 %.Increased the protective enzyme activity of the roots but reduced the content of MDA.The soil enzyme activity increased,urease,phosphatase,sucrase,and catalase activities increased by 269.9 %,157.5 %,60.8 % and 66.7 %,respectively.The number of bacteria in soil was increased,that of fungi was decreased,and bacteria/fungi was6.5 times than that of the control;the community structure of soil fungi was changed,Shannon and Simpson index decreased,and Evenness and Richness index increased;fungal T-RFLP analysis showed that many T-RFs existed only in the treated soil,and the copy number of F.oxysporum was reduced by 51.6 %.4.0,0.05 %,0.2 % and 0.5 % T.erecta air-dried powder were added to apple replanted soil,and the 0.2 % addition treatment had the best alleviation effect on apple replant disease.Plant height,ground diameter,the dry weight in shoot and root of Malus hupehensis Rehd was 3.6 times,1.5 times,8.1 times and 13.1 times to the control,respectively.The net photosynthetic rate increased by 46.7 %;the P point value of the OJIP curve increased,but the K point and the J point value decreased,which alleviated the performance degradation of the electron acceptor side of PSII reaction center;the non-photochemical quenching process was alleviated and the light energy was mainly consumed by the photochemical reaction pathway.The root length,root surface area,root volume and root tip of the seedlings increased by226.5 %,333.0 %,548.4 % and 142.7 %,respectively,and the root respiration rate increased by 155.3 %;the protective enzyme activities of roots increased and the MDA content decreased.The content of soil phenolic acids decreased,with phlorizin,phloretin,cinnamic acid,p-hydroxybenzoic acid and benzoic acid content decreased by 71.8 %,87.6 %,89.1 %,83.0 % and 90.1 %,respectively.Soil organic matter,nitrate nitrogen,ammonium nitrogen,available phosphorus and available potassium were increased;soil enzyme activity was significantly increased.The number of bacteria and actinomycetes in soil increased,and the number of fungi decreased,so the bacteria/fungi increased.The community structure of soil fungi was changed.Shannon,Evenness and Richness index decreased,Simpson indexincreased.The copy number of Fusarium was reduced by 57.9 %.The soil tended to harden if T.erecta powder was added too much,and using powder processing was costly and difficult to realize in the actual production.5.T.erecta straw granules were used for apple replanted soil with the treatment of 0,12.0 g/kg,30.0 g/kg and 60.0 g/kg,30.0 g/kg was the best.The trend of plant growth index and soil environmental index was consistent with that of 0.2 % T.erecta air-dried powder.Ace,Chao and Shannon index of soil bacteria increased,and Simpon index decreased,but the diversity index of fungi shows an opposite trend.Different additions of T.erecta resulted in a significant increase in Bacteroidetes,0.0 g/kg and 12.0 g/kg had a similar bacteria composition,with large proportion of Lactococcus and Bacillus;Pseudarthrobacter and Roseiflexus dominated in 30.0 g/kg treatment;the proportion of Pseudarthrobacter was the highest in 60.0 g/kg treatment.The fungi composition of each treatment was similar,but the proportion was different.12.0 g/kg and 30.0 g/kg treatment increased Ascomycota,and treatment with 60.0 g/kg increased Basidiomycota.The proportion of Humicola and Mortierella.in all treatments was the highest.The Fusarium treated by T.erecta was significantly reduced,which was 91.4 %,94.4 % and 97.1 % lower than 0.0 g/kg,respectively.6.Under field condition,0.5 % addition of T.erecta straw granules treatment was the best in Dashaling and Fengmaozhai area,and Wantou Village with 1 % addition treatment.The plant height,ground diameter and shoot growth was significantly better than the control.The soil enzyme activity was higher in T.erecta treatment,and the trends in three test points were inconsistent.The bacteria number was the highest in mixed planting soil with T.erecta,and the fungi reduced significantly of 0.5 % and 1 % treatment.The fungi of Fengmaozhai and Wantou Village were mainly Ascomycota,Basidiomycota and Zygomycota.At the test site of Fengmaozhai,the reduction of Basidiomycota fungi of mixed planting tretment was the largest.The proportion of Pseudeurotium decreased,and that of Penicillium increased significantly,with 0.5 % treatment the largest.At the test site of Wantou Village,all the treatments increased the Ascomycota and the Zygomycota.The proportion of Mortierella and Penicillium increased significantly,and 1% treatment increased the most..7.The volatile components of dried T.erecta samples were mainly composed of sesquiterpenes,monoterpenes,alcohols,ketones,esters and other hydrocarbons,the content of caryophyllene,farnesene,limonene and basilene was high.The low concentration of caryophyllene and farnesene had a poor inhibition effect on the four Fusarium,in the concentration of 180 mL/L,the inhibition rate of caryophyllene and farnesene was0.8 %-3.6 % and 2.0 %-2.9 %,respectively.In the concentration of 360 mL/L,the inhibition rate of caryophyllen and farnesene were 22.7 %-25.6 % and 18.6 %-21.3 %,respectively.The volatile componnets of T.erecta could inhibit the mycelium growth and spore germination of Fusarium as a result of synergistic and multi-target effects of various components. |
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