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United States Department of Agriculture

Agricultural Research Service

Research Project: REDUCING SOYBEAN YIELD LOSSES THROUGH GENETIC IMPROVEMENT Title: Co-inoculation with rhizobia and arbuscular mycorrhizal fungi inhibited soybean red crown rot: from field study to plant defense-related gene expression analysis

Authors
item Gao, Xiang -
item Lu, Xing -
item Wu, Man -
item Pan, Ru -
item Tian, Jiang -
item Li, Shuxian
item Liao, Hong -

Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 20, 2012
Publication Date: March 21, 2012
Citation: Gao, X., Lu, X., Wu, M., Pan, R.Q., Tian, J., Li, S., Liao, H. 2012. Co-inoculation with rhizobia and arbuscular mycorrhizal fungi inhibited soybean red crown rot: from field study to plant defense-related gene expression analysis. PLoS One. 7(3):e33977.

Interpretive Summary: Soybean red crown rot is an important disease of soybean which severely affects soybean production. We investigated the effects of rhizobia (bacteria inside root nodules that can fix nitrogen) and arbuscular mycorrhizal fungi (help plants to capture nutrients from the soil) under different phosphorus additions on the disease severity of soybean red crown rot in a field with acid soil. Our results indicated that rhizobia and arbuscular mycorrhizal fungi could directly inhibit pathogen growth and reproduction, and activate the plant overall defense system through increasing defense-related gene expressions. Combined with optimal phosphorus fertilization adding rhizobia and arbuscular mycorrhizal fungi can be considered an efficient method to control soybean red crown rot in acid soils.

Technical Abstract: 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. We investigated the disease incidence and index of soybean red crown rot under different phosphorus additions in field and found that inoculation of rhizobia and arbuscular mycorrhizal fungi (AMF) could affect soybean red crown rot, particularly without phosphorus addition. Further studies in sand culture experiments also showed that inoculation with rhizobia or AMF significantly decreased incidence and index of soybean red crown rot, especially when co-inoculation with rhizobia and AMF at low phosphorus level. The root colony forming unit (CFU) decreased over 50% when inoculated by rhizobia and/or AMF at low phosphorus level. However, phosphorus 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. 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 phosphorus fertilization, adding rhizobia and AMF can be considered an efficient method to control soybean red crown rot in acid soils.

Last Modified: 10/25/2014
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