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Efficiency of Plant Growth-promoting Rhizobacteria (pgpr) for the Enhancement of Rice Growth

M. Ashrafuzzaman
Professor
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Farid Akhtar Hossen
Researcher
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, Bangladesh

M. Razi Ismail
Professor
Institute of Tropical Agriculture, University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia

Md. Anamul Hoque
Researcher
Department of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh.

M. Zahurul Islam
Researcher
Division of Soil Science, Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh

S.M. Shahidullah
Senior Scientific Officer
Rice Farming Systems Division, Bangladesh Rice Research Institute, Gazipur-1701

Sariah Meon
Researcher
Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

Abstract/ Executive Summary:

Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and enhance plant growth by a wide variety of mechanisms. The use of PGPR is steadily increasing in agriculture and offers an attractive way to replace chemical fertilizers, pesticides, and supplements. Here, we have isolated and characterized the PGPR from the rhizosphere soil of rice field for the enhancement of growth of rice. Rhizosphere soils were collected from different areas of Mymensingh in Bangladesh. Ten isolates of bacteria, designated as PGB1, PGB2, PGB3, PGB4, PGB5, PGT1, PGT2, PGT3, PGG1 and PGG2, were successfully isolated and characterized. Subsequently, to investigate the effects of PGPR isolates on the growth of rice, a pot culture experiment was conducted. Prior to seeds grown in plastic pots, seeds were treated with PGPR isolates and seedlings were harvested after 21 days of inoculation. Isolates PGB4, PGT1, PGT2, PGT3, PGG1 and PGG2 induced the production of indole acetic acid (IAA), whereas only PGT3 isolate was able to solubilize phosphorus. Most of isolates resulted in a significant increase in plant height, root length, and dry matter production of shoot and root of rice seedlings. Furthermore, PGPR isolates remarkably increased seed germination of rice. Among the ten isolates, PGB4 and PGG2 were found almost equally better in all aspects such as dry matter production, plant height and root length of rice, and IAA production. Isolate PGT3 was also found to be promising in IAA production having an additional property of phosphate solubilization. The present study, therefore, suggests that the use of PGPR isolates PGB4, PGG2 and PGT3 as inoculants biofertilizers might be beneficial for rice cultivation as they enhanced growth of rice, and induced IAA production and phosphorus solubilization.

Keywords: IAA, PGPR, Phosphorus solubilization, Rice growth, Seed germination.

Location: Bangladesh Institute of Nuclear Agriculture, Mymensingh

Start Date: 01-07-2005

End Date: 30-06-2006

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To screen the PGPR strains that are compatible with rice in Bangladesh. It was investigated the effect of PGPR strains on seed germination and growth of rice seedlings as well.

Methodology:

Soil samples were collected from the rhizosphere of 2-month-old rice plants in different areas of Mymensingh district in Bangladesh. The rhizosphere was dugout with intact root system. The samples were placed in plastic bags and stored at 4°C in the Biofertilizer and Microbiology Laboratory of Bangladesh Institute of Nuclear Agriculture. Morphological characteristics of the colony of each isolate were examined on LB agar plates. The culture of 10 isolates were streaked on LB agar plates and incubated at 10, 20, 28, 37 and 45°C. The change in growth and color was observed and recorded after 3 days of incubation. IAA production A single colony of bacterial culture was grown on LB liquid medium. A loopful of the respective culture was transferred to the 100 mL of conical flask containing LB liquid medium with the help of a sterile inoculation needle. The flask was then incubated for 7 days on a rotary shaker. The cultures in the flask showed dense milky white growth were tested for purity (Bric et al., 1991). Phosphate solubilization The plates were prepared with Pikovskya’s medium. The culture of ten isolates were streaked on the plates and incubated in an incubator at 28°C for 7 days. The plates were then examined and data were recorded (Pikovaskya, 1948). Rice seeds (Oryza sativa L. cv. BINA Dhan5) collected from Agronomy Division of Bangladesh Institute of Nuclear Agriculture were soaked in H₂SO₄ for 5 min and washed with sterile water three times to remove the H₂SO₄. Then seeds were treated with bacterial strain for 30 min. Twenty five seeds were placed on agar (2%, w/v) plates and incubated for 3 days in the dark. Finally, germination of seeds was recorded. The bacterial inoculants were prepared according to the method of Vincent (1970). A loopful of the respective rhizobacterial isolate was transferred to the liquid medium of 100 mL conical flask and incubated for 7 days on a rotary shaker. When the cultures in the flask showed dense milky white growth, the broth cultures (>1 x 107 cells/mL) were tested for purity and growth. Ten bacterial isolates were designated as PGB1, PGB2, PGB3, PGB4, PGB5, PGT1, PGT2, PGT3, PGG1 and PGG2. Rice seeds were soaked in H₂SO₄ for 3 min and washed with sterile water seven times. Seeds were then treated with bacterial isolates for 30 min. No treated seeds with any isolate were designated as control. Sands collected from Biofertilizer Laboratory of Bangladesh Institute of Nuclear Agriculture were sterilized by autoclaving. An amount of 0.3 kg sand was placed into a plastic pot. Ten seeds were sown at 4 to 5 cm depth of sand in each plastic pot. Rice plants were harvested after 21 days of seed sowing through separating of plants from soil. The plants were washed through dipping into a vessel. Plant height (cm plant-1) and root length (cm plant-1) of each plant were recorded. Dry weights of shoot and root were recorded after drying in an oven for 1 day at 70°C. Data was analyzed statistically by F-test. The significance of differences between mean values was evaluated by DMRT (Duncan’s New Multiple Range Test).

Source of Information: African Journal of Biotechnology Vol. 8 (7), pp. 1247-1252, 6 April, 2009

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Taken together, results suggest that PGPR are able to induce the production of IAA, solubilization of phosphorus, and resistance to pathogens and pests, thereby improving growth of plants. The use of PGPR as inoculants biofertilizers is an efficient approach to replace chemical fertilizers and pesticides for sustainable rice cultivation in Bangladesh. Further investigations, including efficiency test under greenhouse and field conditions, are needed to clarify the role of PGPR as biofertilizers that exert beneficial effects on plant growth and development.

Knowledge Management: Journal