Diversity Analysis Of Rhizobacterial Community Of Halophytes And Isolation And Screening Of Salt-Tolerant Growth-promoting Rhizobacteria

The research on the diversity of rhizosphere microbial community of typical halophytes in Ningxia saline-alkali land,and the screening of saline-tolerant rhizosphere growth-promoting bacteria are of great significance to the management of saline-alkali soil.This study focuses on two saline-alkali land in Shizuishan City,Ningxia,and analyzes the degree of salinization based on physical and chemical properties;select three typical local halophytes,Kalidium foliatum,Suaeda glauca and Phragmites australis.Use high-throughput sequencing to study the bacterial community structure of the rhizosphere soil;use culture methods to isolate and screen salt-tolerant plant growth-promoting bacteria,and clarify the formulation of microbial agents;verify the growth-promoting and prevention of microbial agents through flat test and pot experiment disease effect.The main results are as follows:(1)Comparing the physical and chemical properties of rhizosphere soils of 2 saline-alkali soils and 3 plant species,the results showed that the pH range of Huinong and Pingluo samples were 9.30?9.41 and 8.22?8.46,and the alkalinity ranges were 28.53%?28.70%and 12.76?12.94%,the mass fraction of full salt is 2.86?3.07 g·kg-1 and 1.96?2.05 g·kg-1,respectively.The salinization degree,available potassium and the mass fraction of available nitrogen in Huinong were significantly higher than those in Pingluo.The mass fraction of organic matter in the two plots is relatively low.Huinong belongs to the severe saline-alkali soil,and Pingluo belongs to the moderate saline-alkali soil.The rhizosphere soil urease activity and alkaline phosphatase activity of the two plots are the highest in Suaeda glauca and Phragmites australis.The invertase activity and catalase activity in the rhizosphere of Kalidium foliatum was the highest.The soil urease activity,alkaline phosphatase activity and invertase activity of Pingluo were higher than Huinong,while the catalase activity table was lower than Huinong.(2)The high-throughput sequencing method was used to analyze and study the bacterial community diversity in the rhizosphere soil of 3 halophytes in 2 plots.The results show that at the phylum level,Proteobacteria,Actinobacteria and Bacteroidetes are dominant bacterial groups in all soil samples,which are generally represented by abundance of Pingluo higher than Huinong.At the genus level,Halomonas,Marinobacte,Thioalkalispira and Planctomyces are four main genera with the highest abundance of soil bacteria.Among them,the relative abundance of Halomonas was the highest,ranging from 25%to 35%,and the abundance of rhizosphere soil of Suaeda glauca in two plots was higher than Kalidium foliatum and Phragmites australis.RDA analysis showed that soil catalase activity had the greatest correlation with the bacterial community diversity in rhizosphere of three plants.(3)83 strains of culturable bacteria were isolated and screened from rhizosphere soil of halophytes.Among them,PJ10 and HY5 have ability to fix nitrogen,dissolve phosphorus,dissolve potassium,produce IAA,iron carrier and ACC deaminase activity.HL3 only has strong nitrogen fixation,phosphorus solubilization ability and ACC deaminase activity.Three strains can tolerate environmental stress with NaCl concentration 120 mmol·L-1 and pH 10.00.PJ10,HY5 and HL3 were identified as Bacillus muralis,B.pumilus and B.atrophaeus,respectively.(4)Adopt confrontation culture,use seed germination test and pot experiment to determine the germination and growth-promoting effects of PJ10,HL3 and HY5 on the seeds and watermelon seedlings of different compound schemes.In the seed germination test,PJ10/HL3 inoculum increased the germination rate of watermelon and white clover seeds under normal culture conditions by 54.22%and 30.31%,respectively.Under the stress condition of NaCl concentration 100 mmol·L-1 and pH 9.00,the inoculum increased the germination rate of watermelon seeds by 54.05%and 45.95%,respectively.Both PJ10 and HL3 have antagonistic ability against Fusarium wilt of watermelon,and the antibacterial rate of combination is 39.61%,which is significantly higher than single bacteria.In the pot experiment,compared with CK,PJ10/HL3 inoculant significantly increased plant height,root length,stem thickness,fresh weight,root volume and root surface area of melon seedlings,and made leaf catalase and superoxide dismutation.Significantly increase leaf catalase,superoxide dismutase,and peroxidase activities.Significantly reduce the incidence and disease index of watermelon fusarium wilt.Compared with the single application of the inoculum or organic fertilizer,the microbial agent is combined with organic fertilizer,and has a more significant growth-promoting effect on melon seedlings under salt-alkali stress.