The Growth Promoting Effect of Bacillus amyloliquefaciens SQ-2 on Rice

doi:10.13560/j.cnki.biotech.bull.1985.2023-0770

Abstract

Abstract:

【Objective】 To study the growth-promoting characteristics of a strain of Bacillus amyloliquefaciens SQ-2 isolated and screened in the laboratory, and to determine the concentration range, mechanism of action, and changes in soil microbiota induced by this strain to promote rice growth.【Method】 The phosphorus solubility and nitrogenase activity of strain SQ-2 were detected using the molybdenum blue colorimetric method and ELISA nitrogenase kit. Inoculating10², 10⁴, 10⁶, 10⁸, and 3×10⁸ CFU/mL bacterial suspension into hydroponic and soil cultured rice, the dry and fresh weight, length, and thickness of the roots and stems of hydroponic and soil cultured rice were measured, respectively after 14 and 20 d of cultivation. Meanwhile, the activities of urease, protease, and sucrase in soil cultured rice were determined using the phenol sodium hypochlorite colorimetric method, the ninhydrin detection method, and the 3,5-dinitrosalicylic acid colorimetric method. Besides, the soil pH value was determined using the pH meter potential method and the content of nitrogen, phosphorus, and potassium available in soil and the activity of acid phosphatase were detected by utilizing the corresponding reagent kit. Analysis of rhizosphere bacterial community structure in soil cultured rice soil was inoculated with 3×10⁸ CFU/mL components.【Result】 The dissolution of tricalcium phosphate by strain SQ-2 was 229.63 mg/L, and the nitrogenase activity was 55.07 U/L. Compared with the control, the dry and fresh weight of hydroponic rice roots showed the most significant increase at an inoculum suspension concentration of 10⁴ CFU/mL. At a vaccination concentration of 3×10⁸ CFU/mL, the dry and fresh weight of soil cultivated rice rhizomes increased most significantly. As the concentration of the inoculum suspension increased, the activities of various enzymes and the concentration of available nitrogen, phosphorus, and potassium in the soil increased to varying degrees, the soil pH value while inoculating strain 3×10⁸ CFU/mL decreased from 7.83 to 7.26. The inoculant strain SQ-2 changed the colony composition in the rice rhizosphere soil and significantly increased Ace, Chao, Sobs and Shannon indices of soil α-diversity.【Conclusion】 B. amyloliquefaciens SQ-2 had different growth promotion effects on soil culture and hydroculture rice. In soil culture experiments, the growth-promoting effect is notably pronounced through the augmentation of soil enzyme activity, rapid increases in available nitrogen, phosphorus, and potassium levels, and alterations in the soil microbial community structure. Overall, these experimental findings offer valuable insights into new strain resources for the development of bacterial fertilizer.

Key words: Bacillus amyloliquefaciens, promoting growth, dissolving phosphorus and fixing nitrogen, soil enzyme activity, rhizosphere bacteria, rice, bacterial community

LI Xue, LI Rong-ou, KONG Mei-yi, HUANG Lei. The Growth Promoting Effect of Bacillus amyloliquefaciens SQ-2 on Rice[J]. Biotechnology Bulletin, 2024, 40(2): 109-119.

Figures/Tables 10

Fig. 1 Phosphorus dissolution of Bacillus amyloliquefaciens SQ-2 in inorganic phosphorus medium A: Phosphate solubilization zones of B. amyloliquefaciens SQ-2 on inorganic phosphorus solid medium; B: phosphorus dissolution amount, pH and bacterial growth ability（1×107）of B. amyloliquefaciens SQ-2 in inorganic phosphorus liquid medium

Fig. 2 Scanning electron micrograph of potassium feldspar after inoculation with B. amyloliquefaciens SQ-2 A: Potassium feldspar control group（2 μm）. B: Morphology of potassium feldspar after inoculation with B. amyloliquefaciens SQ-2（2 μm）. C: Potassium feldspar control group（1 μm）. D: Morphology of potassium feldspar after inoculation with B. amyloliquefaciens SQ-2（1 μm）

Table 1 Effects of B. amyloliquefaciens SQ-2 at different inoculum concentrations on the dry and fresh weight, stem length, and stem diameter of hydroponic rice

处理 Treatment	根干重 Dry weight of root/g	茎干重 Dry weight of stem/g	根鲜重 Fresh weight of root/g	茎鲜重 Fresh weight of stem/g	茎粗 Stem thickness/mm	株高 Height/cm
CK	0.03±0.001c	0.03±0.001c	0.32±0.014b	0.34±0.012ab	0.53±0.020ab	4.92±0.060ab
S1	0.03±0.003c	0.03±0.002bc	0.32±0.002b	0.28±0.010b	0.59±0.020ab	5.28±0.177ab
S2	0.05±0.003a	0.04±0.003a	0.52±0.005a	0.40±0.026a	0.62±0.007a	5.63±0.003a
S3	0.04±0.002ab	0.04±0.001ab	0.42±0.033ab	0.34±0.019ab	0.60±0.007ab	5.71±0.253a
S4	0.04±0.003ab	0.04±0.001abc	0.42±0.007ab	0.36±0.017ab	0.50±0.033b	5.58±0.167a
S5	0.04±0.002bc	0.03±0.001c	0.40±0.024b	0.27±0.004b	0.52±0.010b	4.54±0.180b

Table 2 Effects of B. amyloliquefaciens SQ-2 at different inoculum concentrations on the dry and fresh weight, stem length, and stem thickness of soil cultured rice

处理 Treatment	根干重 Dry weight of root/g	茎干重 Dry weight of stem/g	根鲜重 Fresh weight of root/g	茎鲜重 Fresh weight of stem/g	茎粗 Stem thickness/mm	株高 Height/cm
CK	0.07±0.001bc	0.03±0.001b	0.81±0.038bc	0.43±0.004c	0.72±0.023bc	10.99±0.243c
S1	0.06±0.001c	0.03±0.001b	0.74±0.031c	0.42±0.006c	0.64±0.003c	11.85±0.180c
S2	0.08±0.002abc	0.03±0.001b	0.94±0.022abc	0.42±0.005c	0.72±0.043bc	11.34±0.013c
S3	0.09±0.002ab	0.03±0.001b	0.99±0.017ab	0.46±0.001bc	0.77±0.037abc	10.67±0.067c
S4	0.10±0.001a	0.04±0.002b	1.11±0.001a	0.51±0.037ab	0.87±0.107ab	12.32±0.377c
S5	0.10±0.005a	0.05±0.001a	1.16±0.009a	0.58±0.003a	0.94±0.001a	12.24±0.493c

Fig. 3 Effects of B. amyloliquefaciens SQ-2 on soil cultured rice under different bacterial inoculum concentrations A-F indicates adding different concentration of bacteria; A: 3×108; B: 108; C: 106; D: 104; E: 102; F: 0（CFU/mL）

Fig. 4 Effects of B. amyloliquefaciens SQ-2 at different concentrations on nitrogen, phosphorus, potassium, pH and enzyme activity in soil The different lowercase letters indicate significant differences (P < 0.05)

Fig. 5 Correlation between soil nutrient composition, soil enzyme activity, and pH after inoculation with B. amyloliquefaciens SQ-2（n=18） *P<0.05; ** P<0.01; *** P<0.001

Fig. 6 Shannon dilution curve and Venn plot of B. amylo-liquefaciens SQ-2 A: Alpha diversity index Shannon dilution curve. B: Venn plot of rhizosphere soil microbiota of inoculated Bacillus amyloliquefaciens SQ-2 and control group. CK as the control group, S5 at 3×108 CFU/mL concentration. The same below

Fig. 7 Diversity analysis of soil bacteria *** P<0.001, ns indicate a nonsignificant difference

Fig. 8 Analysis of bacterial community composition in rice rhizosphere soil A: Phylum classification of bacteria in rice rhizosphere soil. B: Class classification of bacteria in rice rhizosphere soil

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