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Shemshura Olga, Candidate of biological sciences, senior researcher, LLP "Scientific-Production Center for Microbiology and Virology"
Almaty, Kazakhstan E-mail: olgashemshura@mail.ru
Suleimenova Zhanara, Candidate of biological sciences, senior researcher, LLP "Scientific-Production Center for Microbiology and Virology"
Almaty, Kazakhstan Ultanbekova Gulnar, Candidate of biological sciences, senior lecturer, Al-Farabi Kazakh National University Almaty, Kazakhstan E-mail: ultanbekova77@mail.ru Mombekova Gulnaz, MSc, researcher, LLP "Scientific-Production Center for Microbiology and Virology" Almaty, Kazakhstan
Rakhmetova Zhanar, MSc, researcher, LLP "Scientific-Production Center for Microbiology and Virology" Almaty, Kazakhstan
EFFECT OF UV IRRADIATION OF PGPR BACTERIA ON SEEDS GERMINATION AND PLANT GROWTH OF MUNG BEAN (VIGNA RADIATA)
Abstract. Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and enhance plant growth. The strains of Pseudomonas putida 4/1, Azotobacter chroococcum P-29 and Bacillus subtilis were allowed for UV irradiation for different time intervals to cause mutation and observed for their consequent action on the seeds germination and plant growth of mung bean (Vigna radiata). The 1% survival of bacterial isolates was resulted in the samples, treated with UV irradiation for 60 min. The mutant strains of Pseudomonas putida M-1, Azotobacter chroococcum M-1 and Bacillus subtilis M-1 were found effective to enhance the germination energy of mung bean seeds compared to parent strains. Moreover, treatment of the mung bean seeds with mutant strain of Bacillus subtilis M-1 had a significant stimulation effect on plant growth. The length of the stems and roots of mung bean treated with Bacillus subtilis M-1 increased significantly in comparison with parent strain in 2, 3 and 1, 3 times, respectively.
Keywords: PGPR bacteria, Mutagenesis, Nitrogen fixation, Vigna radiate.
Introduction growth hormone and nutritional balance, induce the immune
The increasing demand for crop production with a signifi- system of plants, antagonist with phytopatogen and dissolve cant reduction of synthetic chemical fertilizers and pesticides the nutrients to be easily absorbed by plants [3]. For decades, use is a big challenge nowadays. The use of PGPR has been varieties of PGPR have been studied and some of them have proven to be an environmentally sound way of increasing crop been commercialized, including the species of Pseudomonas, yields by facilitating plant growth. Plant growth promoting rhi- Bacillus, Enterobacter, Klebsiella, Azobacter, and Serratia [4]. zobacteria (PGPR) are beneficial bacteria that colonize plant Strain improvement is an essential part of process devel-
roots and enhance plant growth [1]. The use of PGPR could in- opment. Induced mutagenesis is widely used for selection crease the yield of agricultural crops and that is an environmen- of microorganisms producing biologically active substances tally friendly step. They help in increasing nitrogen fixation (le- and further improving of their activities. Strain improvement gumes); promoting free-living nitrogen-fixing bacteria; supply is usually done by classical mutagenesis which involves ex-of macronutrients; production of plant hormones. They also posing the microbes to physical mutagens such as ultraviolet enhance the growth of other beneficial microbes and control rays. Induced mutagenesis by using UV rays for selection of the other biotic stress causing agents [2]. PGPR could regulate microorganisms to produce biologically active substances and
EFFECT OF UV IRRADIATION OF PGPR BACTERIA ON SEEDS GERMINATION AND PLANT GROWTH OF MUNG BEAN (VIGNA RADIATA)
improvement of their activities have been known effective [5]. The present study was focused on strain improvement of bacterial strain through mutation and to assess the enhancement or reduction of mung bean (Vigna radiata) growth.
Materials and Methods. The objects of the study were bacterial strains of Pseudomonas putida 4/1, Azotobacter chroococcum P-29 and Bacillus subtilis from the own collection of microorganisms. The cultures were maintained on King B agar (Pseudomonas putida 4/1), pea agar (Azotobacter chroococcum P-29), meat-peptone agar (Bacillus subtilis) and stored at 4 °C. All bacterial strains were subjected to UV mutagenesis at the range of260 nm. 4 mL of bacterial suspension were poured aseptically into a sterile Petri dish. The exposure to UV rays was conducted in a dark chamber with UV lamp. The distance from the UV lamp to Petri dish was around ± 60 cm with a treatment time of 30, 45 and 60 min. During the exposure, petri dish cap was opened and all the other sources of light were cut off. After that, suspension was transferred into sterile test tubes covered with a black paper and kept in the refrigerator overnight to avoid photo reactivation. Next day, suspension of each treatment was serially diluted with
sterile distilled water, plated on to nutrient agar medium and incubated for 24 h at 28 °C. The number of colonies in each plate was calculated [6].
The effect of the obtained PGPR mutant strains on the seeds germination and plant growth of mung beans was studied according to GOST [7]. The seeds germination and plant growth of mung bean was observed by placing the mung bean seeds on rhizosphere soil in seed trays. Germinated seeds were soaked in 3 ml mutant bacterial strains for 15 minutes. Growth of the germinated seeds was observed at regular intervals.
All the analyses were performed in triplicate, and the results were expressed as mean SD values of the three sets of observations [8].
Results and Discussion. The effect of the obtained mutant strains of PGPR bacteria on the germination and energy of germination of the mung bean seeds was studied. The energy of germination of mung bean seeds was determined on the 4th day after seeds treatment with culture liquid as well as the germination of the mung bean seeds was determined on the 7th day. The obtained data are presented in (Tablel).
Table 1. - Effect of mutant PGPR strains on germination energy and germination of mung bean (Vigna radiata) seeds before and after UV irradiation
PGPR strains 100 seeds Length, cm
germination energy,% (after 4 days) germination,% (after 7 days) root stem
mutant Control (water) 62 80 3.7 ± 0.3 7.8 ± 0.2
P. putida М-1 91 100 16.5 ± 0.2 11.4 ± 0.3
A. chroococcum М-1 100 100 5.3 ± 0.2 9.2 ± 0.3
B. subtilis М-1 100 100 5.4 ± 0.2 22.7 ± 0.3
parent P. putida 4/1 82 100 6.9 ± 0.2 12.9 ± 0.3
A. chroococcum Р-29 89 100 3.1 ± 0.2 7.6 ± 0.2
B. subtilis 72 100 4.1 ± 0.1 9.5 ± 0.1
As can be seen from the data presented in (Table l), found that Bacillus subtilisM-1 mutant strain had a significant treatment of the mung bean seeds with the mutant strains of stimulation effect on plant growth. The length of the stems
P. putida М-1, A. chroococcum M-1 and B. subtilis M-1 with and roots of mung bean plants treated with B. subtilis M-1 in-
1:1 concentration had a positive effect on germination en- creased in comparison with parent strain in 2, 3 and 1, 3 times,
ergy of seeds compared to the parent strains. Moreover, it was respectively.
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Funding: This research work was funded by Ministry of Education and Sciences of the Republic of Kazakhstan (Grant № AP05132359).
