Studying Effect of Plant Growth-Promoting Rhizobacteria on Ecophysiological Traits of Soybean (Glycine max L.) under Irrigation Regimes
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Article Type:
Research/Original Article (دارای رتبه معتبر)
Abstract:
Introduction

Water scarcity and frequent droughts are becoming a serious problem particularly in the context of alarming predictions of climate change in the world. Within the arid and semi-arid regions, water availability is a major limitation for crop production. Thus, it is necessary to improve yield and the efficient utilization of limited available water in the irrigated agroecosystems. One possibility to enhance crop yield under water limitation is using soil microorganisms that increase the radiation and water efficiency and uptake capacity. Among these potential soil microorganisms, plant growth-promoting rhizobacteria (PGPR) are the most promising, including all bacteria inhabiting the rhizosphere and the rhizoplane able to simulate plant growth and yield. Therefore, the objective of the present study was to evaluate the effects of the PGPR on the ecophysiological characteristics of soybean under different moisture regimes.

Material and Methods

The field experiment was conducted during 2016 at the research farm of Campus of Agriculture and Natural Research, Razi University, Kermanshah, Iran (34°, 19´ N, 47°, 50´ E with 1320 m altitude). A split plot factorial experiment was conducted based on randomized complete block design. Main plots had three irrigation regimes in which irrigation was cut based on the soybean stages (I1: water deficit stress from mid pod development stage to maturity stage; I2: water deficit stress from grain filling development stage to maturity stage; and I3: optimum irrigation in all development stages) and sub-plots were composed of plant growth-promoting rhizobacteria (PGPR) (B1: no bacteria; B2: Bacillus subtilis; and B: Bacillus licheniformis) and soybean cultivar (TMS, M9 and Kosar). The experimental plots were irrigated based on furrow method. I3 treatment were irrigated every 7 days until the end of the growing period while in the I1 and I2 treatments, the plots were irrigated every 7 days until the start of the water deficit stress. In order to inoculate with the PGPR, the soybean seeds were plunged in a 1:10 (v:v) solution of liquid culture and distilled water, respectively for 10 minutes. All seeds including inoculated and no inoculated seeds oven-dried at 30 ℃ for 5 h. Finally, the soybean inoculated seeds by PGPR were inoculated by Rhizobium japonicum before sowing and cultivated immediately at 4 to 5 cm soil depth. The evaluated traits were the leaf area index (LAI), radiation absorption (RA), crop growth rate (CGR), relative growth ratio (RGR), total dry weight (TDW), radiation use efficiency (RUE) and Grain yield (GY).

Results and Discussion

The results indicated that the water deficit stress reduced the LAI, RA, CGR, RGR, TDW, RUE and GY of soybean. The PGPR application improved all measured traits of soybean in all irrigation regime treatments. The highest LAI (6.7), RA (18.2 MJ.m-2), CGR (20.6 g.m-2.d-1), TDW (1104.7 g.m-2) and RUE (1.165 g.MJ-1) were related to TMS cultivar in the optimum irrigation and B. licheniformis treatment and the lowest them were related to Kosar cultivar under water deficit stress from mid pod development stage to maturity stage and no bacteria treatment. The greatest GY (380.9 g.m-2) was related to TMS cultivar which was observed in the optimum irrigation and B. licheniformis treatment and the lowest GY (134.2 g.m-2) was related to Kosar cultivar which was observed in the water deficit stress from mid pod development stage to maturity stage and no bacteria treatment. In this study, B. licheniformis compared to B. subtilis presented a more effective improvement in soybean LAI, RA, CGR, RGR, TDW, RUE and GY.

Conclusion

It seems that the PGPR could promote the soybean growth and yield via increasing the root system and more uptake of water in the rhizosphere. Nevertheless, as the results showed, the more effects of the PGPR were observed in the I2 treatment compared to other treatments. The PGPR actually could promote the soybean growth and yield in the mid water deficit stress.

Language:
Persian
Published:
Agroecology journal, Volume:11 Issue: 4, 2020
Pages:
1205 to 1224
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