Screening, Identification of Plant Growth Promoting Rhizobacteria and Its Effect on Reducing Fertilization While Increasing Efficiency in Wheat (Triticum aestivum)
LI Yong-Bin, LI Yun-Long, GUAN Guo-Hua*, CHEN San-Feng*
State Key Laboratory of Agricultural Biotechnology/College of Biology, China Agricultural University, Beijing 100193, China
Abstract：Plant growth-promoting rhizobacteria (PGPR) are microorganisms that live in the rhizosphere and root surface of plants, and can directly or indirectly promote plant growth and development. The application of microbial fertilizers containing plant growth-promoting rhizobacteria can significantly improve the nutritional status and growth of plants. The demand of modern ecological agriculture for non-chemical fertilizers and the improvement of people's awareness of environmental protection make it great potential for the development and research of microbial fertilizers. The collection and preservation of bacterial resources is fundamental to the development of microbial fertilizers, and thus it is extremely important to screen for excellent strains. Therefore, this study collected rhizosphere soil of wheat (Triticum aestivum), maize (Zea mays), tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) grown in Beijing. A total of 500 bacterial strains were isolated and screened with spread plate method, and their plant growth-promoting properties were tested. Through pot experiment in the greenhouse, 15 bacterial strains with excellent growth-promoting effects on tomato seedlings were identified. The 16S rRNA gene sequence analysis revealed that 11 strains 4-L, 14-L, z4-3, z7-2, z13-5, S6, 1-18, Z20-2, Z23-3, Z28-4, Z30-2 were Paenibacillus sp., 2 strains z13-2 and z13-3 were Pseudomonas azotoformans, strain z14-1 was Alcaligenes faecalis, and strain 56 was Bacillus subtilis. On this basis, Paenibacillus sp. S6, 1-18 and B. subtilis 56 with good plant growth-promoting ability were inoculated onto wheat for field plot experiment. In this experiment, 5 kinds of treatment were set, including control 1 (without strain inoculation and the amount of urea was reduced by 10%); control 2 (without strain inoculation and the amount of urea was not reduced), treatment 3 (Paenibacillus sp. S6 was inoculated and the amount of urea was reduced by 10%), treatment 4 (B. subtilis 56 was inoculated and the amount of urea was reduced by 10%), and treatment 5 (Paenibacillus sp. 1-18 was inoculated and the amount of urea was reduced by 10%). At the returning green stage of wheat, the effects of different treatments on the growth of wheat were evaluated. The results showed that the plant height of wheat in treatments 3, 4, 5 was significantly higher than that in control 1 (P<0.05), but had no significant difference from control 2. Similarly, the fresh weight of wheat in treatments 3, 4, 5 was significantly higher than that in control 1 (P<0.05), but had no significant difference from control 2. In addition, wheat yield was counted at maturity. The results showed that under the condition of reducing 10% urea, the yield of wheat inoculated with Paenibacillus sp. S6, Paenibacillus sp. 1-18 and B. subtilis 56 increased by 6.9%, 8.8%, and 10.4% (P<0.05), respectively, compared with the control 1; while there was no significant difference compared with the control 2. The above results indicated that it was feasible to replace 10% of chemical fertilizers with microbial fertilizers containing above 3 strains. Among them, B. subtilis 56 performed best in reducing fertilizer use and increasing yield, and thus it could be demonstrated and promoted on a large scale. This study could provide excellent strain resources for the development of microbial fertilizers, and provide reference for spread and application of the technique using microbial fertilizers replacing some chemical fertilizers.
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