Title Page
Contents
Abstract 8
Chapter 1. INTRODUCTION 9
Chapter 2. MATERIALS AND METHODS 16
2.1. Isolation of endophytic bacteria 16
2.2. Sample preparation of ginseng and isolation of endophytic bacteria 16
2.3. Partial identification of endophytic bacteria by 16S rRNA gene sequence analysis 17
2.3.1. DNA extraction 17
2.3.2. Amplification of 16S rDNA sequencing analysis 18
2.4. Auxin activity test (IAA) 19
2.5. Plate assay for phosphate-solubilizing activity 20
2.6. Test of antagonistic effects 21
2.7. Pepper radicle and seedling assays 22
Chapter 3. RESULTS AND DISCUSSION 23
3.1. Isolation of endophytic bacteria and 16S rDNA analysis 23
3.2. Production of auxin (IAA) 26
3.3. Phosphate-solubilizing activity 29
3.4. Test of antagonistic effects 33
3.5. Pepper radicle and seedling assay 36
3.6. Statistical analysis 37
4. CONCLUSION 47
REFERENCE 48
Abstract (in Korean) 57
Table 1. Identification of isolated strains from Ginseng roots by 16S rDNA sequence analysis. 24
Table 2. The production of auxin (IAA) by 27 diazotrophic bacterial strains 27
Table 3. Phosphate solubilization by endophytic diazotrophic bacterial isolates 30
Table 4. Antagonistic activities of endophytic diazotrophic bacteria 34
Table 5. Effect of endophytic diazotrophic bacteria on pepper growth 38
Table 6. Various biological activities of endophytic diazotrophic bacteria 40
Figure 1. Gel electrophoresis of the amplified 16S rRNA gene of isolated bacteria. The universal primer set of fd1 and rp2 were used to amplify 16S... 25
Figure 2. Standard curve indole-3-acetic acid (IAA) concentration. After mixing the series of IAA concentrations with the Salkowski coloring reagent... 28
Figure 3. Confirmation of phosphate-solubilizing activity by the production of clear zones on NBRIP agar. SG 21001, SG 21003, SG 21004, SG 21006, SG... 31
Figure 4. Standard curve for phosphate solubilization. With 2 replicas per concentration, absorbances were determined at 530nm. Each concentration for... 32
Figure 5. Inhibition of the bacterial strains against Rhizoctonia oryzae, and Rhizoctonia solani. While the fungi were placed on one side of a potato... 35
Figure 6. The growth chamber shows the effect of endophytic diazotrophic bacterial strains on the growth of pepper plants. The plants were grown for 4... 39
Figure 7. Based on the 16S rDNA gene sequences, a phylogram is used to represent the connections between detected bacterial isolates and their... 41
Figure 8. Based on the 16S rDNA gene sequences, a phylogram is used to represent the connections between detected bacterial isolates and their taxonomic similarity to... 42
Figure 9. Based on the 16S rDNA gene sequences, a phylogram is used to represent the connections between detected bacterial isolates and their... 43
Figure 10. Based on the 16S rDNA gene sequences, a phylogram is used to represent the connections between detected bacterial isolates and their... 44
Figure 11. Based on the 16S rDNA gene sequences, a phylogram is used to represent the connections between detected bacterial isolates and their... 45
Figure 12. Based on the 16S rDNA gene sequences, a phylogram is used to represent the connections between detected bacterial isolates and their... 46