title: Co-inoculation with rhizobia and AMF inhibited soybean red crown rot: from field study to plant defense-related gene expression analysis.
abstract: BACKGROUND
  Soybean red crown rot is a major soil-borne disease all over the world, which severely affects soybean production. Efficient and sustainable methods are strongly desired to control the soil-borne diseases.
  
  
  RESULTS
  We firstly investigated the disease incidence and index of soybean red crown rot under different phosphorus (P) additions in field and found that the natural inoculation of rhizobia and arbuscular mycorrhizal fungi (AMF) could affect soybean red crown rot, particularly without P addition. Further studies in sand culture experiments showed that inoculation with rhizobia or AMF significantly decreased severity and incidence of soybean red crown rot, especially for co-inoculation with rhizobia and AMF at low P. The root colony forming unit (CFU) decreased over 50% when inoculated by rhizobia and/or AMF at low P. However, P addition only enhanced CFU when inoculated with AMF. Furthermore, root exudates of soybean inoculated with rhizobia and/or AMF significantly inhibited pathogen growth and reproduction. Quantitative RT-PCR results indicated that the transcripts of the most tested pathogen defense-related (PR) genes in roots were significantly increased by rhizobium and/or AMF inoculation. Among them, PR2, PR3, PR4 and PR10 reached the highest level with co-inoculation of rhizobium and AMF.
  
  
  CONCLUSIONS
  Our results indicated that inoculation with rhizobia and AMF could directly inhibit pathogen growth and reproduction, and activate the plant overall defense system through increasing PR gene expressions. Combined with optimal P fertilization, inoculation with rhizobia and AMF could be considered as an efficient method to control soybean red crown rot in acid soils.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.forename: Xing
authors.initials: X
authors.lastname: Lu
authors.forename: Man
authors.initials: M
authors.lastname: Wu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zhang
authors.forename: Ruqian
authors.initials: R
authors.lastname: Pan
authors.forename: Jiang
authors.initials: J
authors.lastname: Tian
authors.forename: Shuxian
authors.initials: S
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Liao
mesh_terms: D018506:Gene Expression Regulation, Plant; D038821:Mycorrhizae / Q000378:metabolism*; D010935:Plant Diseases; D013025:Glycine max / Q000378:metabolism*