泛菌SZ1在沙枣叶片的定殖动态及促生效果OA

[Objective]To investigate the colonization dynamics of the plant growth-promoting Pantoea SZ1 in phyllo-sphere of Elaeagnus angustifolia,evaluate its effects on seedling growth,physiological traits,phyllosphere microbial di-versity,and community structure,and comprehensively assess its plant growth-promoting effects,thereby providing re-ference for the application of plant growth-promoting bacteria and the development of microbial products.[Method]A rifampicin-resistant strain,SZ1r,was obtained by rifampicin resistance labeling,and its colonization dynamics on the leaf surface and within the leaves of Elaeagnus angustifolia were investigated.The plant growth-promoting traits of SZ1r,including indole-3-acetic acid(IAA)production,phosphate solubilization,and siderophore production,were also evalu-ated.A pot experiment with Elaeagnus angustifolia seedlings was conducted using three treatments:sterile water treat-ment(CK1),five-time-diluted sterile NB medium treatment(CK2),and SZ1r culture suspension treatment(SZ1).The effects of SZ1 strain on seedling growth,relative chlorophyll content(SPAD value),leaf nitrogen content,and antioxi-dant enzyme activities were determined.High-throughput sequencing was further employed to analyze the effects of SZ1 strain on phyllosphere microbial diversity and community structure of Elaeagnus angustifolia,and the functions of the phyllosphere microbial community were predicted to comprehensively evaluate the plant growth-promoting effects of Pan-toea SZ1.[Result]The rifampicin-resistant strain SZ1r obtained by rifampicin resistance labeling exhibited morphological characteristics,phylogenetic relationships,soluble phosphorus and IAA contents,and siderophore activity consistent with those of the parental strain SZ1,indicating that rifampicin resistance labeling did not alter the major characteristics of the strain SZ1r.Under the SZ1 treatment,the population of SZ1r colonizing the interior of Elaeagnus angustifolia leaves initially increased and subsequently decreased,reaching a maximum of 3.75×107 CFU/g at 15 d after inoculation and remaining at 4.70×10⁵ CFU/g at 50 d.These results indicated that Pantoea SZ1 could stably colonize the interior of Elaeagnus angustifolia leaves for at least 50 d.The SZ1 treatment greatly enhanced seedling growth and physiological in-dexes of Elaeagnus angustifolial seedlings.Compared with CK2,root length,seedling height,stem diameter,and fresh weight increased significantly by 62.55%,38.53%,25.60%,and 47.37%respectively(P<0.05;the same below),while the SPAD value and leaf nitrogen content increased by 1.55 and 2.07 times respectively.At 40 d after inoculation,superox-ide dismutase(SOD)activity reached 375.37 U/g,while catalase(CAT)activity peaked at 272.07 U/g in the SZ1 treat-ment;CAT activity was significantly higher than that in CK1 and CK2 by 65.26%and 45.31%respectively.SZ1 treatment also increased the Observed index,Chao1 index,ACE index,and total number of operational taxonomic units(OTU)in the phyllosphere microbial community.At the genus level,the relative abundances of beneficial microorganisms in phyllo-sphere of Elaeagnus angustifolia,including Achromobacter,Sphingomonas,and Pseudopithomyces,were increased by 13.82%,55.56%,and 72.99%respectively compared with CK1,and increased by 30.43%,13.91%,and 20.00%respec-tively compared with CK2.Furthermore,the SZ1 treatment significantly increased the abundance of functional genes as-sociated with carbon and nitrogen metabolism,and secondary KEGG metabolic pathways,and enhanced ecological func-tions of the phyllosphere microbiome,including chemoheterotrophy,aerobic chemoheterotrophy,and nitrogen cycling.[Conclusion]Pantoea SZ1 can stably colonize in phyllosphere of Elaeagnus angustifolia seedlings.Inoculation with SZ1 strain enhances seedling growth and physiological activity,modulates phyllosphere microbial diversity and community structure,and consequently improves the phyllosphere microecological environment.These findings indicate that Pantoea SZ1 has potential for the development of microbial products.