| The banana is the important food and economic crop in sub-tropical areas of South China.However,in recent years,the planting of bananas in these ares is experiencing the unprecedentedly serious threat from banana wilt disesae,resulting in 10%-40%affection rate on average and even 90%affected plants.Some of the banana plantations have to be abandoned.So it is the most urgent issue to advance the research on prevention and control of the banana wilt disesae.For achieving highly-effective and environmentally-friendly preventive cure,this research started with biological prevention by appling the combination of organic fertilizers and B.Amyloliquefaciens selected by our lab to study the preventive effect of banana wilt disesae by experiments of potted plants(substrate and soil)and fieldplanting as well as discuss the prevention and control mechanism from the prospective of content of amino acid in root exudates of banana and soil microbial diversity..Through our research,following results are gained:(1)Under the condition of base substrate culture and soil culture,bio-organic fertilizers can effectively prevent and control the banana wilt disesae,with the prevention effect of 56.2%and 52.7%respectively.Compared with organic fertilizers,sterilizing organic fertilizers and no fertilizers,bio-organic fertilizers can enhance activity of POD and PPO in banana leaves.Different treatments have different significant effects on the total amount,constitution and content of amino acid in root exudates of banana seedlings.During different stages of these treatments,major amino acid is represented by Ala,g-ABA and GluNH2,constituting about 26.0%-46.0%of the total amino acid.Under these two cultivated conditions,compared with organic fertilizers,sterilizing organic fertilizers and no fertilizers,applying bio-organic fertilizers can significantly enhance the content of ASPNH2,Thr,Ser,Ala,Phe,g-ABA and Arg before inoculation,and increase the content of P-Ser after accuring of banana wilt disesae.Besides,compared with sterilizing organic fertilizers and no fertilizers,applying bio-organic fertilizers can also significantly increase the content of PEA,Glu and GluNH2 and reduce the content of Trp and Met after accuring of banana wilt disesae.Relevant analysis shows significant negative correlation between the disease index of banana wilt disesae and the content of P-Ser and Glu,while significant positive correlation between the disease index and the content of Met and Trp.It is clearly shown that under both cultivated conditions applying bio-organic fertilizers can lower the disease index of banana wilt disesae is related to the the constitution and content of amino acid in banana root exudates.(2)Biolog-Eco method shows applying bio-organic fertilizers can better increase rhizospheric soil microbial AWCD value,utilization of six carbon sources(P<0.05),species richness and evenness of micro-organisms(Shannon index and McIntosh index)as well as weaken the microbial species dominance(Simpson index),compared with applying organic fertilizers and no fertilizers.PLFA research results show that with the affection of banana wilt disesae the total amount of soil microbial PLFA and bacteria will increase more significantly by applying bio-organic fertilizers than organic fertilizers and no fertilizers and the total amount of fungus and G~+will increase more remarkably than applying no fertilizers.And bio-labeling categories of PLFAs will decrease significantly with the affection of banana wilt disesae even through applying either of those treatments above.The dominant PLFA categories through all those treatments rank as 16:0(pseudomonas),i15:0(bacteria),cy19:0?8c(Burkholderia)and 18:1?9c(fungus),among which 16:0,cy19:0?8c and 18:1?9c are represented as bio-organic fertilizers>organic fertilizers>no fertilizers.DGGE analysis shows applying bio-organic fertilizers can more significantly increase the number of DGGE belt spectrum,lower similarity of rhizospheric soil belt spectrum,enhance the species richness and evenness of rhizospheric soil bacteria(Shannon-Wiener index and Evenness index),and promote the formation of distinctive flora of soil bacteria,compared with organic fertilizers and no fertilizers.These three analysis shows the application of bio-organic fertilizers can enhance the overall activity of micro-organisms and richness and evenness of bacteria,promote the formation of dominant flora,and improve the micro-ecological environment of soil,which is closely connected with the development of the banana wilt disesae.Applying bio-organic fertilizers can improve the micro-ecological environment of soil so as to suspend the occurrence and spread of the banana wilt disesae.(3)The experimental results of applying bio-organic fertilizers in the field and pot reach an agreement that applying bio-organic fertilizers can effectively suspend the occurrence of the banana wilt disesae and lower the disease index from 64.37 by applying chemical fertilizers and 57.34 by organic fertilizers to 33.26,with an overall control effect of 48.3%.Compared with organic fertilizers and chemical fertilizers,bio-organic fertilizers can more significantly enhance the basal respiration and substrate-induced respiration of rhizospheric soil micro-organisms,FDA hydrolas activity,utilization of carbon sources by rhizospheric soil micro-organisms,species richness and evenness of microbiota and AWCD value.The principal component analysis demonstrates that the function and structure of carbon metabolism vary greatly in different treatments.Through applying bio-organic fertilizers,the rhizospheric soil microbial activity can be enhanced.Compared with organic fertilizers and no fertilizers,applying bio-organic fertilizers can better use polymers,carbonhydrates and phenolic carbon sources,which further shows that application of bio-organic fertilizers can reduce the harm of the banana wilt disesae through improving the soil microbial activity,categories and environment.(4)In order to explore the different influence of biochar and organic fertilizers on micro-ecological environment,research has been conducted to compare the influence of applying biochar and various fertilizers on soil microbial functional diversity.The results show that 0.1%organic fertilizers and 0.25%biochar can more significantly enhance the utilization of carbon sources by soil micro-organisms than other fertilizers,but further increase of biochar rates(more than 0.25%)would reduce AWCD values.Besides,0.1%organic fertilizers can significantly enhance the soil microbial evenness while 0.25%biochar can significantly enhance the species richness and evenness of soil micro-organisms;0.1%organic fertilizers and 0.25%biochar have the highest utilization of polymers,carbonhydrates,carboxylic acid,amino acid,and phenolic carbon sources.Applying more phosphate fertilizers can enhance the utilization of carbon sources by soil micro-organisms,while applying nitrogen fertilizers and potassic fertilizers can significantly weaken the utilization of carbon sources by soil micro-organisms.The major components analysis shows that 0.1%organic fertilizers,0.1%biochar,0.25%biochar have similar microbial carbon metabolism structures;applying only organic fertilizers or appropriate biochar will have more significant influence on soil microbial community structure than mixed fertilizers;applying chemical phosphate fertilizers and adding appropriate biochar in chemical fertilizers can change the utilization rate of carbon sources by soil micro-organisms.All these above results prove that organic fertilizers and appropriate biochar have similar influence on soil microbial functional diversity and appropriate biochar can replace organic fertilizers to be the bio-control absorbant. |
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