| Soil salinity,as a major problem in agriculture,is one of the most important environmental pressures in the world.The reduction of crop yield,the sharp decline in productivity,and the result of crop physiological toxicity(disease)caused by soil salt stress have attracted a lot of attention.Using plant growth-promoting rhizobacteria(PGPR)to alleviate plant salt stress is an economically friendly and important ecological method that is conducive to sustainable development of agricultural.In this study,salt-tolerant and growth-promoting bacteria were screened from the rhizosphere soil of well-grown plants in multiple saline habitats,and the strains of salt-tolerant PGPR were inoculated in the rhizosphere of tomato(Solanum lycopersicum)seedlings for greenhouse pot experiment.By measuring and analyzing the biomass,root morphology,photosynthetic parameters and ion distribution of tomato under different salinity stress,the effects of different salt-tolerant strains on the regulation of salt-tolerance of tomato seedlings were discussed.The impact of high-throughput sequencing technology on the structure and diversity of indigenous soil microbial communities in the rhizosphere of tomato under different salinity was preliminarily evaluated after salt-tolerant and probiotics treatment.The main results are as follows:1.From the rhizosphere soil of 6 different saline habitats,a total of 65 strains of salt-tolerant and pro-growth rhizosphere bacteria were obtained through screening of salt-tolerant and pro-growth properties.Among them,27 strains have IAA-producing properties,and the best strain is Bacillus siamensis KCTC 13613;15 strains can produce siderophores,and the best strain is Pseudomonas punonensis CECT 8089;17 strains have nitrogen fixation properties,and the best strain is Pseudomonas punonensis CECT 8089;27 strains can produce ACC deaminase,and the best strain is Bacillus aryabhattai B8W22.There are 7 strains with three or more growth-promoting properties,belonging to Pseudomonas spp.,Bacillus spp.,Halomonas spp.and Glutamicibacter spp..2.The different strains of salt-tolerant PGPRs B9(Pseudomonas punonensis CECT 8089),D5-2(Bacillus siamensis KCTC 13613)and Y4(Halomonas olivaria C17)were inoculated into tomato seedlings respectively,all of them had different effects on the growth of tomato seedlings under salt stress.In general,B9 showed the best growth-promoting effect in increasing tomato stem diameter and root tip number,regardless of the salinity;with the increase of salinity,the promoting effect of Y4 on plant height and the promoting effect of D5-2 on root volume were significantly better than other treatment.In addition,D5-2 had the best performance on tomato photosynthesis in the non-salt and 2.5 ‰ NaCl treatment.In terms of ion balance,under high salt stress and low salt stress,the three microbial agents can effectively reduce the excessive absorption of Na in tomato,and increase the absorption of K,Ca and Mg,so as to increase the K/Na,Ca/Na and Mg/Na and promote the ion balance in tomato.3.After inoculation of three microbial agents,the Alpha diversity and Beta diversity of tomato rhizobacteria under different salinity were changed.After the addition of three microbial agents,the Alpha diversity of rhizobacteria increased to varying degrees.In terms of increasing the richness of bacterial communities,the treatmen inoculated with B9 were most abundant in non-saline conditions,and Y4 had the highest abundance under low salt conditions,while D5-2 had the best effect under high salt conditions.According to Beta diversity data,at each salinity level,there were significant differences in species composition between the three PGPR-inoculated and non-inoculated treatment groups,especially the treatment of D5-2.In summary,the three strains selected in this study can promote the growth of tomato seedlings under salt stress and non-salt stress,and improve the community composition of the rhizosphere bacteria and the abundance of dominant flora to some extent. |
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