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Cjm-2017-0571.Pdf Canadian Journal of Microbiology Salt-tolerant and plant growth-promoting bacteria isolated from high-yield paddy soil Journal: Canadian Journal of Microbiology Manuscript ID cjm-2017-0571.R4 Manuscript Type: Article Date Submitted by the 10-Apr-2018 Author: Complete List of Authors: Shi-Ying, Zhang; Yunnan Institute of Microbiology; Yunnan Agricultural University Cong, Fan; Yunnan Institute of Microbiology; Yunnan Agricultural University Yong-xia, Wang; Yunnan Institute of Microbiology Yun-sheng, Xia; Yunnan Agricultural University Wei, Xiao; Yunnan Institute of Microbiology Xiao-Long,Draft Cui; Yunnan Institute of Microbiology Rice, plant-growth promoting bacteria, diversity, salinity tolerance, 1- Keyword: aminocyclopropane-1-carboxycarboxylate deaminase Is the invited manuscript for consideration in a Special Not applicable (regular submission) Issue? : https://mc06.manuscriptcentral.com/cjm-pubs Page 1 of 33 Canadian Journal of Microbiology 1 Salt-tolerant and plant growth-promoting bacteria isolated from high-yield paddy soil 2 3 Shiying Zhang 1, 2 , Cong Fan 1, 2 , Yongxia Wang 1, Yunsheng Xia 2, 4 Wei Xiao 1, Xiaolong Cui 1 5 1 Yunnan Institute of Microbiology, Yunnan University, Kunming, China 6 2 Yunnan Engineering Laboratory of Soil Fertility and Pollution Remediation, Yunnan Agricultural 7 University, Kunming, China 8 These authors contributed equally to this work. Draft Correspondence Xiaolong Cui, Yunnan Institute of Microbiology, Yunnan University, Kunming, 650091, PR China. Tel:86-871-65033543, E-mail: [email protected]. Wei Xiao, Yunnan Institute of Microbiology, Yunnan University, Kunming, 650091, PR China. Tel:86-871-65033543, E-mail: [email protected]. 1 https://mc06.manuscriptcentral.com/cjm-pubs Canadian Journal of Microbiology Page 2 of 33 9 Abstract: Growth and productivity of rice is negatively affected by soil salinity. However, some 10 salt-tolerant bacteria improve plant health in saline stress. In this study, 305 of bacteria were isolated 11 from paddy soil in Taoyuan, China. Among these, 162 strains were tested its salt-tolerance, 67.3%, 12 28.4%, and 9.3% of the strains could grow in media with NaCl concentrations of 50, 100, and 150 g/L, 13 respectively. The phylogenic analysis to 74 of 162 strains indicates that these bacteria belong to 14 Bacillales (72%), Actinomycetales (22%), Rhizobiales (1%), and Oceanospirillales (4%). Among 162 15 strains,30 salt-tolerant strains were screened for their plant-promoting activities under axenic 16 conditions at 3, 6, 9 and 12 g/L NaCl, 43-97% of the strains could improve rice germination energy or 17 germination capacity, while 63-87% of the strains could increase shoot and root lengths. Among 18 various PGPB, TY0307 was the most effective strain for promoting the growth of rice, even at high salt 19 stress. This was associated with its production of 1-aminocyclopropane-1-carboxycarboxylate 20 deaminase, IAA and siderophore, and inducing accumulation of proline, while reducing the salt 21 induced malondialdehyde content. These Draftresults suggest that several strains isolated from paddy soil 22 could improve rice salt tolerance and may be used in the development of biofertilizer. 23 Keywords: Rice, plant-growth promoting bacteria, diversity, salinity tolerance, 24 1-aminocyclopropane-1-carboxycarboxylate deaminase 2 https://mc06.manuscriptcentral.com/cjm-pubs Page 3 of 33 Canadian Journal of Microbiology Introduction Salinity is a major factor that detrimentally affects crop productivity worldwide. According to Food and Agricultural Organization (FAO) report, more than 800 million hectares of land and 20% of irrigated agricultural land are affected by salinity around the globe in 2008 (Singh and Jha, 2016). In addition, anthropogenic global warming is exacerbating the problem, causing secondary salinization (García-Cristobal et al., 2015). Because of its growth conditions, rice (Oryza sativa) is particularly susceptible to salt stress (Kohler et al., 2009; Hong et al., 2009; Lucas et al., 2014). In many rice production areas, salt stress limits yield (García-Cristobal et al., 2015). A number of approaches are used to address the negative impacts of salinity, including gypsum applications, organic matter amendments, and irrigation optimization to limit the quantities of salts applied and to effectively leach salts from the root zone, and planting salt-tolerant crop varieties (Nadeem et al., 2016). The use of beneficial bacteria, known as plant-growth promoting bacteria (PGPB), to increase the productivity of agriculturalDraft crops under stress conditions and decrease the use of chemical fertilizers and pesticides that have a strong negative impact on the environment is becoming an increasingly intriguing biotechnological alternative (Saharan and Nehra, 2011). A number of reports demonstrate the efficacy of PGPB in promoting plant growth under normal conditions as well as in saline soils and other stressed environments (Saharan and Nehra, 2011; Egamberdieva, 2009; Zahir et al., 2003, 2009; Bernardr et al., 2007; Nadeem et al., 2014). These bacteria promote plant growth either by directly providing nitrogen, phosphorous, and iron nutrition, stimulating plant growth by production of phytohormones, dissolved phosphorus, or indirectly by inhibiting the growth of pathogenic microorganisms (Nadeem et al., 2016; Dimkpa et al., 2009). The effectiveness of PGPB in mitigating the adverse effects of salinity stress has been reported for several vegetable and other crop plants (Zahir et al., 2009; Mayak et al., 2004). Among these strains, only a small number can improve the salt resistance of rice (García-Cristobal et al., 2015; Yuan et al., 2016; Jha and Subramanian, 2014; Nautiyal et al., 2013; Forni et al., 2016). Since the existence of rich microorganisms in hypersaline environments was discovered in the early 20th century, a large number of bacteria and archaea have been isolated from hypersaline environments, e.g., salt mines, salt fields, ancient salt crystals, and pickled food (Xiao et al., 2013). 3 https://mc06.manuscriptcentral.com/cjm-pubs Canadian Journal of Microbiology Page 4 of 33 According to FAO standards (Brouwer et al., 1985), soil with a salt concentration of 0-3 g/L in the water extracted from a saturated soil is considered non-saline soil. However a small number of studies have found salt-tolerant bacteria in non-saline soil (Chen et al., 2010; Echigo et al., 2005). Surprisingly, researcher discovered a large number of halophiles and salt-tolerant bacteria in non-saline soils, Bacillaceae was the most frequently occurring family. Yet, where these salt-tolerant bacteria come from is unclear. With respect salt-tolerant bacteria widely distributed in other non-saline soil, it is hypothesized that salt-tolerant bacteria can be isolated from paddy soil, and these salt-tolerant bacteria can be correlated with improved rice growth under salt stress. Taoyuan village, Yunnan province of China, which was reported in several papers with the high rice yields above 13 t/ha, has been famous as a special eco-site for rice high yield due to its superior light and temperature conditions (Katsura et al., 2008; Li et al., 2009). The aim of the present study was to provide the first detailed characterization of salt-tolerant bacteria in high-yield paddy soil in Taoyuan village, and examine their effectDraft on plant growth, osmolyte content of rice plants growing under salt stress. Materials and Methods Sample collection: Paddy soil samples were collected from Taoyuan village（35° 56' N, 104° 08' W） on December, 2010. Paddy soil approximately 5-10 cm beneath the ground surface was collected. Sampling was performed at five locations, and the samples were mixed together. All samples were collected into sterilized sample bags using a small sterilized shovel and transported to the laboratory at room temperature. Microbial isolation was performed within 24 h. Soil salt content was determined to be 1.01 g/kg using the NY/T1121.16-2006 method (Chinese Agricultural Standard). According to FAO standards, the collected samples were non-saline soils. Culture medium: R2A (1 L): yeast extract 0.5 g, peptone 0.5 g, soluble starch 0.5 g, casein acid hydrolysate 0.5 g, glucose 0.5 g, K2HPO4 0.3 g, MgSO4 0.024 g, sodium pyruvate 0.3 g. Modified LB (MLB, 1 L): tryptone 1 g, yeast extract 0.5 g, NaCl 0.5 g, sodium pyruvate 2 g. Marine broth agar (MBA, 1 L): peptone 5.0 g, yeast extract 1.0 g, ferric citrate 0.1 g, sodium chloride 19.45 g, magnesium chloride 8.8 g, sodium sulphate 3.24 g, calcium chloride 1.8 g, potassium chloride 0.55 g, sodium bicarbonate 0.16 g, potassium bromide 0.08 g, strontium chloride 34.0 mg, boric acid 22.0 mg, 4 https://mc06.manuscriptcentral.com/cjm-pubs Page 5 of 33 Canadian Journal of Microbiology sodium silicate 4.0 mg, sodium fluoride 2.4 mg, ammonium nitrate 1.6 mg, disodium phosphate 8.0 mg, agar 15.0 g. Strain isolation: Three types of media were employed as isolation media. To each medium, 16 mg/L of nystatin was added. A 10 g soil sample was placed in an Erlenmeyer flask that contained 90 ml sterilized 0.85% (w/v) NaCl solution and glass beads. The flask was placed on a shaker for 2 h at 120 r/min at room temperature to yield a soil suspension. Next, a 10× gradient dilution was performed using 0.85% (w/v) NaCl solution. The 0.2 ml soil suspension with dilution at 10-5-10-7 was plated on medium and cultured at 28℃. After 7-30 days, single colonies were cultured in a corresponding medium for the streaking isolation of tetrads. The obtained pure cultures were freeze-dried in milk, subsequently inoculated onto a slant culture medium, and stored at 4℃ for future use. Evaluation of NaCl tolerance of the isolates: To test NaCl tolerance, isolates growth at various NaCl concentrations (0, 50, 100, 150, and 200 g/L) was investigated on R2A.
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