Research On Biological Control Of Mikania Micrantha Based On Puccinia Spegazzinii

Mikania micrantha is one of the key invasive organism under agricultural and forestry control in china,which is also one of the most harmful weeds in tropical and subtropical area.In the existing methods,control of M.micrantha is facing huge challenges in global.Traditional chemical control is threating to soil microorganisms,water sources,and human and animal health.Therefore,biological control has become new way to prevent the spread of M.micrantha.Puccinia spegazzinii is a pathogenic fungus that lives on M.micrantha.As far as we know,P.spegazzinii only living on M.micrantha,and without invasive for non-target organisms.In this study,we fouce on structure of microbial community of diseased area and safety of P.spegazzinii for non-target organisms and the effect of M.micrantha growth under P.spegazzinii stress.So,our study evaluatly the potential for bio-control of P.spegazzinii and provide a theoretical basis for the research and development of new control technologies of M.micrantha.The main conclusions are as follows:1.Identification of the microbial community of M.micrantha rustIn this study,we used the Illumina MiSeq sequencing technology to determine the microbial community of M.micrantha rust spot by the 16sRNA V5-V6 sequence of the bacteria and the ITS1 sequence.The results showed that the average relative abundance of Ascomycota was the highest among fungi,accounting for 51.88%of the total.The average relative abundance of Proteobacteria was the highest,accounting for 94.72%of the total bacteria.The average relative abundance of P.spegazzinii belonging to Ascomycetes ranks third in the level of Fungi with an average relative abundance of 11.74%.In conclusion,the rust spots of M.micrantha contained a variety of microorganisms,even plant pathogenic fungi and bacteria,which may be the result of the interaction of a variety of microorganisms.2.The symptoms of M.micrantha rust and safely assessment of P.spegazziniiAccording to observe the symptoms and pathogenesis process of M.micrantha rust,the infection process of P.spegazzinii was divided into four stages.Stages:1)The initial appearance of chlorotic spots;2)The yellowing of the lesions without pustules;3)The initial appearance of pustules;4)The maturation of pustules.In addition,host specificity testing of P.spegazzinii was conducted against 63 species of plants in 30 families.The infectivity of P.spegazzinii to plants was evaluated based on pustules and symptoms.The results showed that,the P.spegazzinii can not infect these plants except M.micrantha,indicating that it has no infectivity to non-target plants.It proves again that P.spegazzinii is a kind of pathogenic fungi with strong host specificity,which lays a foundation for the research and development of pathogenic agents for M.micrantha.3.The P.spegazzinii effect on growth and physiology of M.micranthaAfter infected by P.spegazzinii,the M.micrantha leaves turned yellow and withered,and the stem are deformity and growing slowly,which could lead to the death of the plant in severe cases.We also found that when the M.micrantha leaves were infected by P.spegazzinii,the number of leaves,the number of branches,the total length of stem,the length of stem,the dry weight of the above ground and the ratio of leaf weight to leaf area significantly changes.Especially,the dry weight of the above ground decreaded 1.94 times.All content of phytohormones related to plant growth decreased except ethylene.In particular,the content of auxin,cytokinin,and gibberellin related to stem growth were decreased,which these as low as 0.43,0.41,0.17 times.Adenosine triphosphate(ATP)content of M.micrantha has increased significantly after infected by P.spegazzinii,which these increased by 2.18 times.In addition,the results of the transcriptome and metabolome before and after the infected by P.spegazzinii showed that the contents of 74 metabolites were significantly different between the treatment and the control group,and 82.43%of the metabolites were significantly reduced.Based on transcriptome data,a total of 4978 differential expressed genes(DEGs)were identified,including 2924 down-regulated DEGs and 2054 up-regulated DEGs.Based on the integrated analysis of metabolomics and transcriptome,it was found that after infected by P.spegazzinii,the plants consumed a large amount of glucosaccharide,malic acid and isocitric acid by increasing the expression levels of key genes in the glycolysis and the TCA cycle,and produced a large amount of ATP to maintain the growth of the plants.