| Intensive management of hickory(Carya cathayensis)has led to soil deterioration,companied with the occurrence of serious root rotting.The pathogens infecting hickory root is mainly genus Fusarium fungi.Those hickory trees infected would result in leave withering and dropping,root necrosis and finally whole tree dying,which caused great economic loss.In order to ascertain the characteristics of soil microbial community characteristics,root zone soil samples with four disease grades were collectedin hickoryforest,they are respectively healthy(JK),first level(B1),second level(B2),third level(B3)in serious order.Soil samples around healthy trees which were under three different fertilization practices(SF1,SF2,SF3).Soil physical and chemical properties,7 types of enzyme activity,the abundance of soil bacteria and fungi,and pathogens F.oxysporum and F.graminearum,were analyzed.The community structure and alpha diversity of soil bacteria and fungi were measured through high-throughput sequencing.In order to develop a biological control fertilizer for prevent from disease of root rot,the inhibitory effects of available antibiotic strains of Bacillus amyloliquefaciens subsp.Plantarum,Trichoderma,and Penicilliumoxalicum were clarified through dual culture method in flat panel and mixed cultivation in soil.Afterword,antibiotic strains mixed with commercial organic fertilizer to make bio-organic fertilizer.The outdoor pot fertilizer experiment by plantingsmall hickory tree was carried out to observe its growth promotion and disease inhibition effect of developed bio-organic fertilizer.The main results are as follows:1.The comparison of soil in root zone of Carya cathayensis forest with different disease grades showed that the average value of each index of healthy soil(JK)was higher than that of diseased soil,and it showed an overall downward trend with the increase of disease degree.The lower the nutrient and p H were,the more serious the disease was.Among the soil microbial enzyme activities,protease(AG),cellulose disaccharide hydrolase(CB),?-glucosidase(BG)and N-acetyl-?-glucosaminidase(NAG)had the highest activities in healthy soil,showing a trend that the more serious the disease symptoms were,the lower the enzyme activity was,while leucine aminopeptidase(LAP),phosphatase(PHOS)and ?-xylosidase(XYL)showed a fluctuation trend that first decreased and then recovered.The bacterial gene abundance showed a downward trend as a whole,and the fungal abundance was still the highest in healthy soil,showing a trend of first decreasing and then increasing.Soil bacterial diversity indexes JK and B1 were higher than those of B2 and B3(P<0.05),while fungal B3 was significantly lower than that of other soils(P<0.05).The absolute dominance of the three bacterial communities(Proteobacteria,Acidobacteria and Actinomycetes)of all soil bacteria was consistent.Rokubacteria and Latescibacteria were the characteristic groups of healthy soil,while Campylobacter was the characteristic group of seriously diseased soil.In the diseased soil,the abundance of Soliopsis increased,while the abundance of Rhizobium and Mycococcus decreased.The community structure of soil JK and B3 fungal phylum was similar,B1 and B2 were similar.Fusarium oxysporum increased with the increase of disease severity,but the highest abundance of Fusarium graminearum appeared in B1 soil,significantly higher than the other three treatments(P< 0.05).Soil organic carbon,available phosphorus,available potassium and other indicators were closely and positively correlated with ?-glucosidase(BG),N-acetyl-?-glucosaminidase(NAG)and bacterial and fungal diversity(P< 0.05).The bacterial community was less affected by the environment,and the fungal community was more affected by the environment.2.Comparison of different fertilization methods of Carya cathayensis forest root soil results showed that different fertilization methods of Carya cathayensis forest soil nutrients differences,but the overall nutrient is sufficient to meet the growth of Carya cathayensis.Different fertilization had little effect on the activity of seven enzymes and gene abundance of bacteria,but had more effect on gene abundance of fungi than bacteria.Fertilization had little effect on bacterial diversity,and fungal diversity showed the order of SF3 > SF2 > SF1(P<0.05),indicating that fertilization could improve the diversity of soil fungi in Carya cathayensis forest land to some extent.Fertilization had little effect on bacterial community structure in soil,and the main bacterial were Proteus,Acidobacter and Actinomycetes.The more fertilizer types were applied,the higher the abundance of ascomycetes was,The increase of ascomycota abundance would lead to the decrease of basidiomycetes abundance.Fertilization had a great influence on the growth of fungi,but the regularity was poor.There was no significant difference in the relative abundance of mesomycetes,fecal crustaceans and bespore molds in three healthy soils.Combined with the results of the previous chapter,it was speculated that these three fungal communities were related to health.The number of pathogenic bacteria in healthy Carya cathayensis forest was low and did not reach the disease abundance.3.The results of biocontrol effect,fertilizer development and pot experiment on biocontrol bacteria showed that Bacillus amyloliquefaciens,Trichoderma acanthoxylum and Penicillium oxalicum could inhibit the growth of Fusarium oxysporum and Fusarium graminearum,but the inhibitory mechanisms were different.In the confrontation culture on the plate,Trichoderma acanthoxylum had the best effect,followed by Penicillium oxalicum and Bacillus.The three biocontrol bacteria can inhibit the growth of pathogens in simulated diseased soil,but the effect is not stable.The inhibitory effect of mixed application of two or three strains was worse than that of single strain,indicating that these three biocontrol strains were not suitable for simultaneous mixed application.The three biocontrol bacteria can survive in bio-organic fertilizer,and can reach the national microbial organic fertilizer bacteria quantity standard after 6 months.The application of biological organic fertilizer can promote the growth of Carya cathayensis,and the effect of WK1 fertilizer is the most significant.Application of fertilizer increased the abundance of bacteria and fungi in soil,and also inhibited two pathogens.In summary,the occurrence of Carya cathayensis root rot is the result of comprehensive factors such as soil physical and chemical properties,enzyme activity,decreased abundance and diversity of bacteria and fungi,and increased abundance of pathogenic bacteria.Supplementing nutrients,improving soil p H and applying biological organic fertilizer containing biocontrol bacteria can reduce the abundance of pathogenic bacteria in soil and alleviate the root rot of Carya cathayensis.The developed biological organic fertilizer can be used for the prevention and treatment of Carya cathayensis root rot. |
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