大豆根际促生菌的分离、鉴定及其耐盐促生作用OA北大核心CSTPCD

[Objective]Plant growth-promoting rhizobacteria(PGPR)can effectively promote plant growth through long-term mutualistic symbiosis with plants.The objective of this study is to screen and identify rhizosphere growth-promoting actinomycetes from soybean rhizosphere soil and clarify their growth-promoting mechanisms,and to lay a foundation for the development and utilization of microbial agents.[Method]Different actinomycetes were collected using soil dilution coating method and plate streak inoculation method.The growth-promoting characteristics of isolates were analyzed using phosphorus solubilization,potassium solubilization,and siderophore assay media.Through microscopic observation,physiological and biochemical experiments,and multi-gene sequence analysis,the target growth-promoting actinomycetes were identified.Different salt concentrations(0-10%)were set to determine the salt tolerance of the target isolate.The growth-promoting ability of the isolate on soybean seedlings was detected by pot experiments and whether spraying the culture medium of the isolate under salt stress conditions could improve the stress resistance of soybean plants was evaluated.[Result]Thirteen PGPR isolates were screened and obtained.Among then,the Sg-7 isolate not only had strong abilities to dissolve phosphorus,potassium,siderophore,and IAA production,but also effectively antagonized Pseudomonas syringae pv.glycinea(Psg).Based on morphological characteristics,biochemical,and multi-gene analyses,the soybean rhizosphere growth-promoting bacterium Sg-7 was identified as Streptomyces griseocarneus.The Sg-7 strain had certain salt tolerance characteristics,with a maximum tolerance to 7%NaCl salt concentration.Pot experiments showed that the diluted culture fluid after irrigation could effectively promote the germination of soybean seeds and improve growth indicators such as root length,stem diameter,fresh weight,and leaf area.Under 150 mmol·L-1 salt stress,irrigation with a 50×dilution of the Sg-7 culture fluid could effectively enhance SOD enzyme activity of soybean leaf,which was 1.84 times that of the salt stress treatment group.The CAT enzyme activity after irrigation with 100×dilution of culture fluid was 4.33 times higher than that of the salt stress treatment group.The POD enzyme activity after irrigation with 10×dilution of culture fluid was 1.10 times that of the salt stress treatment group.The culture fluid of Sg-7 strain could also enhance the root activity of soybean plants and promote the increase of carotenoid content in leaves to resist stress,which was 3.05 and 1.12 times that of salt stress treatment group,respectively.[Conclusion]S.griseocarneus Sg-7 strain is a potential plant rhizosphere growth-promoting bacterium with broad development potential and practical application value.