Abstract
Abstract: Problem statement: Pseudomonas spesies are one of the rihizobacterial group that have an important role in plant growth promoter and plant health. To prepare them as inoculants, they must have a range of characters as growth promoter such as Indole Acetic Acid (IAA) producers which can promote the growth of plants and solubilize phosphates. In addition, they must also have the various characters that act as biocontrol agents such as siderofor, chitinase and anti-fungal compound producers. Approach: Pseudomonas sp isolated from soybeans rhizospere and identified based on physiological reactions and 16S rRNA gene sequences. Various tests for the determination of the growth promoter were based on IAA production, phosphate solubilization and growth promoter of length of root and stems and number of lateral roots of soybean sprouts. Test of siderophore, chitinase, as well as anti anti-fungal compounds productions to inhibit the growth of Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii, were used as a biocontrol agent determination. Hypersensitivity test was used to screen for Pseudomonas sp classified as non-pathogenic rhizobacteria. Results: Fourteen isolates identified as a non-pathogenic Pseudomonas sp that produced IAA and Promoted enhancement of root length, shoot length, or number of lateral root. Among those 14 isolates, 8 isolates showed phosphate solubilizing activity, 12 isolates capable of producing siderophore and six isolates were observed to have chitinolytic activity. Only three isolates were able to inhibit the growth of Fusarium oxysporum in high level. While one and two isolates inhibited Sclerotium rolfsii and Rhizoctonia solani in high level, respectively. Conclusion: On the basis of excellent growth promoter and biocontrol activities, we recommended 5 isolates of Pseudomonas sp which were Crb-3, Crb-16, Crb-17, Crb-44 and Crb-94 as potential isolates of Pseudomonas sp that could be applied as inoculants of soybean plant.
Highlights
Bacteria that inhabit the rhizosphere may influence plant growth by contributing to a host plant's endogenous pool of bioactive compounds such as phytohormones, antibiotics, siderophores (Patten and Glick, 2002; Mubarikf et al, 2010)
The objectives of this study were to (i) isolate Pseudomonas sp from the soybean rhizosphere, (ii) screen the abilities and the possession of plant growth promoting attributes include the production of Indole Acetic Acid (IAA) hormone and siderophore, root elongation, phosphate solubilization, chitinase activity and the ability to inhibit pathogenic fungi Fusarium oxysporum, R. solani and Sclerotium rolfsii the causal agent of root rot disease in soybean
The chitinolytic index was measured by Pseudomonas spp. was isolated from rhizosphere soil of using formula: (Ø clear zone- Ø colony) ÷ Ø colony
Summary
Bacteria that inhabit the rhizosphere may influence plant growth by contributing to a host plant's endogenous pool of bioactive compounds such as phytohormones, antibiotics, siderophores (Patten and Glick, 2002; Mubarikf et al, 2010). Those kind of bacterial group are well-known as Plant Growth Promoting Rhizobacteria (PGPR). Indirect effects are related to production of metabolites, such as antibiotics, siderophores, or HCN, that decrease the growth of phytopathogens and other deleterious microorganisms. Direct effects are dependent on production of plant growth regulators or improvements in plant nutrients uptake (Bai et al, 2003)
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