| Mulberry bacterial wilt is one of the destructive soil borne diseases and caused by Ralstonia solanacearum.The morbidity of 3 year continuous mulberry fields is over 85%,which causes huge economic losses and becomes the main bottleneck of the sericulture production and sustainability in tropical areas.Rhizosphere microbial community is closely related to the occurrence of plant soil borne diseases.In this paper,the changes of microbial community in mulberry rhizosphere soil respectively treated with microbial fertilizer and new lime nitrogen fertilizer were analyzed by high-throughput sequencing technology,while the correlation with soil physical and chemical properties was also analyzed,which were aimed to develop a new technology of controlling mulberry bacterial wilt based on regulation of rhizosphere microbial community structure.The results are as follows:1.The application of microbial fertilizer and new lime nitrogen fertilizer all could effectively control the mulberry bacterial wiltThe mulberry seedlings were cultivated in naturally occurring soil and additionally inoculated with 108 cfu/g Ralstonia solanacearum.The mulberry branches of the negative control group without fertilization showed typical symptoms of bacterial wilt,and about 2×103 cfu/g bacterial wilt pathogens were detected in the roots,while the fertilization group was healthy;indicating that both root irrigation with Lvnonglin? No.41 microbial fertilizer(which was activated and irrigated by 250 times)or mixing soil with Yuzhongao?new lime nitrogen(biomass,silicon,calcium,magnesium,potassium fertilizer,50 kg/mu),could effectively decrease the relative abundance of pathogenic microflora,then prevent and control the occurrence of mulberry wilt.2.Effects of microbial fertilizer treatment on microbial community structure(1)Compared with the non fertilization control group(sense),the relative abundance of bacteria such as Verrucomicrobia(76.62%),Planctomycetes(76.40%)were significantly increased,while Firmicutes(56.02%)and Bacillus(53.57%)were significantly decreased.More over,the relative abundance of fungi such as Talaromyces(445.12%),Penicillium(821.72%)were significantly increased,while Olpidiomycota(97.14%),Mortierellomycota(87.29%),Mortierella(88.60%)were significantly decreased.These indicated that microbial fertilizer could reconstruct the microbial community of mulberry rhizosphere soil mainly by regulating the abundance of beneficial fungi and reducing the harmful bacteria.(2)Compared with the anti-bacterial wilt mulberry group(Anti),the relative abundance of bacteria such as Verrucomicrobia(50%),Planctomycetes(33.33%),were significantly increased,while Proteobacteria(7.06%)were significantly decreased.More over,the relative abundance of fungi such as Penicillium(840.72%)and Clonostachys(1200%)were significantly increased,while Chytridiomycota(74%),Mortierellomycota(77.32%),Cladosporium(92.56%)and Mortierella(78.10%)were significantly decreased.These indicated that the reconstructed microbial community of mulberry rhizosphere soil by microbial fertilizer was significantly different from that of resistant mulberry,which focused on improving the relative abundance of beneficial fungi to against bacterial wilt.3.Effects of new lime nitrogen fertilizer treatment on microbial community structure(1)Compared with the non fertilization control group(sense),the relative abundance of bacteria such as Verrucomicrobia(95.24%),Ralstonia(150%)were significantly increased,while Bacillus(67.86%)were significantly decreased.More over,the relative abundance of fungi such as Penicillium(405.05%)and Rozellomycota(74.07%)were significantly increased,while the Cladosporium(70.76%)were significantly decreased.Although the relative abundance of beneficial bacteria or fungi were significantly increased,the relative abundance of Ralstonia solanacearum also significantly increased after new lime nitrogen fertilizer treatment,indicating that the stability of the microbial community of rhizosphere soil reconstructed by new lime nitrogen fertilizer treatment may be lower than that reconstructed by microbial fertilizer.(2)Compared with the anti-bacterial wilt mulberry group(Anti),the relative abundance of bacteria such as Verrucomicrobia(65.81%),Ralstonia(400%),Acidobacteria(26.56%),were significantly increased,while Proteobacteria(11.18%),WPS-2(20.80%,Firmicutes(55%),were significantly decreased.More over,the relative abundance of Penicillium(415.46%)was significantly increased,while Chytridiomycota(89.82%and Cladosporium(85.45%)were significantly decreased.These indicated that although new lime nitrogen fertilizer treatment could prevent and control mulberry bacterial wilt,the stability of soil microbial community was also lower than that of resistant mulberry varieties.4.Difference of microbial community between microbial fertilizer and new lime nitrogen fertilizerAt the phylum level of bacteria,the relative abundances of Proteobacteria,Acidobacteria,in the microbial fertilizer group were higher than those in the new lime nitrogen fertilizer group,while the relative abundances of Actinobacteria in the microbial fertilizer group was decreased by 10.81%than those in the new lime nitrogen fertilizer group.At the genus level of bacteria,the relative abundances of Uncultured-bacterium-c-AD3,Bacillus and were increased by 18.35%and 44.44%respectively.More over,the relative abundances of Ascomycota,Talaromyces in microbial fertilizer treatment group were higher than those in new lime nitrogen treatment group.The results showed that the relative abundance of beneficial bacteria,especially fungi,was higher after microbial fertilizer treatment,and the stability of reconstructed microbial community structure was higher than that of new lime nitrogen fertilizer treatment.5.Effects of microbial fertilizer and new lime nitrogen fertilizer on the soil physical and chemical propertiesThe soil organic matter(SOM),available phosphorus(AP),available potassium(AK),exchangeable magnesium(EMg)and electrical conductivity(EC)in the microbial fertilizer group were 0.13%,0.27%,0.34%,0.15%and 1.30%higher than those in the new lime nitrogen fertilizer group respectively,while the pH,total phosphorus(TP)andexchangeable calcium(ECa)were 0.02%,0.44%and 0.16%lower than those in the new lime nitrogen fertilizer group respectively.The results indicated that microbial fertilizer could not only regulate microbial community to prevent and control bacterial wilt,but also improve soil physical and chemical properties,which was more conducive to mulberry growth.In conclusion,the application of microbial fertilizer and new lime nitrogen fertilizer all could reconstruct the microbial community of mulberry rhizosphere soil and improve the relative abundance of beneficial bacteria and fungi,to prevent the occurrence of mulberry bacterial wilt;Microbial fertilizer could not only adjust the relative abundance of beneficial fungi and build a more stable microbial community structure,but also improve soil physical and chemical properties,which could promote the mulberry growth;meanwhile the new lime nitrogen fertilizer is more suitable for acid soil and soil improvement to prevent and control the mulberry bacterial wilt. |
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