title: A Complex Inoculant of N2-Fixing, P- and K-Solubilizing Bacteria from a Purple Soil Improves the Growth of Kiwifruit (Actinidia chinensis) Plantlets.
abstract: Limited information is available if plant growth promoting bacteria (PGPB) can promote the growth of fruit crops through improvements in soil fertility. This study aimed to evaluate the capacity of PGPB, identified by phenotypic and 16S rRNA sequencing from a vegetable purple soil in Chongqing, China, to increase soil nitrogen (N), phosphorus (P), and potassium (K) availability and growth of kiwifruit (Actinidia chinensis). In doing so, three out of 17 bacterial isolates with a high capacity of N2-fixation (Bacillus amyloliquefaciens, XD-N-3), P-solubilization (B. pumilus, XD-P-1) or K-solubilization (B. circulans, XD-K-2) were mixed as a complex bacterial inoculant. A pot experiment then examined its effects of this complex inoculant on soil microflora, soil N2-fixation, P- and K-solubility and kiwifruit growth under four treatments. These treatments were (1) no-fertilizer and no-bacterial inoculant (Control), (2) no-bacterial inoculant and a full-rate of chemical NPK fertilizer (CF), (3) the complex inoculant (CI), and (4) a half-rate CF and full CI (1/2CF+CI). Results indicated that significantly greater growth of N2-fixing, P- and K-solubilizing bacteria among treatments ranked from greatest to least as under 1/2CF+CI ≈ CI > CF ≈ Control. Though generally without significant treatment differences in soil total N, P, or K, significantly greater soil available N, P, or K among treatments was, respectively, patterned as under 1/2CF+CI ≈ CI > CF ≈ Control, under 1/2CF+CI > CF > CI > Control or under 1/2CF+CI > CF ≈ CI > Control, indicating an improvement of soil fertility by this complex inoculant. In regards to plant growth, significantly greater total plant biomass and total N, P, and K accumulation among treatments were ranked as 1/2CF+CI ≈ CI > CF > Control. Additionally, significantly greater leaf polyphenol oxidase activity ranked as under CF > 1/2CF+CI ≈ Control ≈ CI, while leaf malondialdehyde contents as under Control > CI ≈ CF > 1/2CF+CI. In short, the applied complex inoculant is able to improve available soil N, P, and K and kiwifruit growth. These results demonstrate the potential of using a complex bacterial inoculant for promoting soil fertility and plant growth.
authors.affiliation: Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest UniversityChongqing, China; Collaborative Innovation Center of Special Plant Industry, Chongqing University of Arts and SciencesChongqing, China; Centre of Excellence for Soil Biology, College of Resources and Environment, Southwest UniversityChongqing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Shen
authors.affiliation: Centre of Excellence for Soil Biology, College of Resources and Environment, Southwest UniversityChongqing, China; School of Plant Biology, University of Western AustraliaCrawley, WA, Australia.
authors.forename: Xinhua
authors.initials: X
authors.lastname: He
authors.affiliation: Collaborative Innovation Center of Special Plant Industry, Chongqing University of Arts and SciencesChongqing, China; College of Forestry and Life Science, Chongqing University of Arts and SciencesChongqing, China.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University Chongqing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Collaborative Innovation Center of Special Plant Industry, Chongqing University of Arts and Sciences Chongqing, China.
authors.forename: Jianming
authors.initials: J
authors.lastname: Tang
authors.affiliation: Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest UniversityChongqing, China; Centre of Excellence for Soil Biology, College of Resources and Environment, Southwest UniversityChongqing, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Guo
keywords: Bacillus spp.; K- and P-solubilizing bacteria; N2-fixation bacterium; identification; malondialdehyde; polyphenol oxidase