| Bacillus is a common gram-positive bacteria in nature.It is widely used in agriculture and animal husbandry production due to the functions of biocontrol,plant growth-promotion,and insecticide.Therefore,it is of great significance to isolate Bacillus with adaptation to stress environment and wide application in agriculture.In this study,we isolated and screened Bacillus strains from the barren soil of desert and farmland in the arid area of northwestern China.The followings were carried out,1)To reveal its diversity and determine the phylogenetic status by 16S r RNA gene sequence analysis;2)To rescreen strains that can antagonize Phytophthora sojae induced root rot and Rhizoctonia solani induced wheat sheath blight through plate antagonism experiments;3)To obtain strains with excellent growth-promoting functions through the growth-promoting related characteristic test;4)finally,to verifies its growth-promoting and stress-resistant effects on crops with inoculating pathogen and bacillus by the plant experiment.The main conclusions obtained are as follows:(1)A total of 202 strains of Bacillus were isolated in this experiment.By 16S r RNA gene sequences analysis,it was found that these strains could be classified into 16 groups,of which including 49 strains related to Bacillus tequilensis(24.2%)and 45 strains related to B.siamensis(21.9%).B.licheniformis(34,16.8%),B.subtilis(18,8.9%),and B.halotolerans(16,7.9%).177 strains of Bacillus were isolated from the poor soil of farmland,which mainly were classified into ten close related Bacillus species,including B.licheniformis(34 strains account for 19.2%),B.siamensis(44,24.8%),of B.tequilensis(49,27.7%);A total of 25 Bacillus strains were isolated from the desert,which mainly were classified into nine close related Bacillus species,including B.halotolerans(10 strains account for 40%),B.pumilus(4,16%),B.tropicus(2,8%),and B.wiedmannii(2,8%)(8%),B.atrophaeus(2,8%),etc.(2)The Bacillus strains were tested against Phytophthora sojae and Rhizoctonia solani,and it was found that 28 Bacillus strains had high antagonistic ability,including 13B.siamensis strains,five B.halotolerans strains,and five B.halotolerans strains.Amomg them,three B.tequilensis strains,two B.subtilis,three B.safensis subsp.safensis,one B.velezensis and B.pumilus had a higher bacteriostatic rate with more than 50%.Tests on the characteristics of phosphate-solubilizing bacteria,degrading organic phosphorus,dissolving potassium,cellulose,and producing iron carriers were carried out,ten strains with 4 kinds of growth-promoting properties were screened,these strains included B.siamensis(six strains),B.subtilis(two strains),B.velezensis(one strain),B.safensis subsp.(one strain)and B.pumilus(one strain).The semi-solid puncture test showed that all ten strains had motility.As while,ten strains of Bacillus can grow in LB liquid medium with5%Na Cl,and the number of bacteria was close to 1.0×10~8 cfu/m L after 24 h,indicating that these strains have high salt tolerance.(3)Ten Bacillus strains can significantly promote crop growth after wheat and soybean were inoculated by Rhizoctonia solani and Phytophthora sojae pathogenic bacteria.The results showed the chlorophyll content is 30%higher than that of control.In the inoculation treatment by strain 2-2,the wheat height and root length were 31%and 18%higher than that of control,respectively.The dry weight of wheat roots and above ground part were 89%and 524%higher than that of control,respectively.The biocontrol efficiency of strain 13-8 for soybeans was 84%.Soybean height and root length are 89%and 31%higher than the control,respectively.The dry weight of roots and above ground part are77%and 35%higher than the control respectively.The results indicated that two strains had significantly higher antagonistic and growth-promoting effects on plants.In summary,two Bacillus strains with excellent growth-promoting and biocontrol functions were obtained from the poor soils in farmland and deserts.They should be the B.siamensis strains with different genotypes be the analysis of the 16S r RNA gene and rec A gene.This research could provide to excellent bacillus strains for the subsequent study and use in biological inoculants for healthy growth of soybean and wheat. |
PDF Full Text Request