title: Root interactions in a maize/soybean intercropping system control soybean soil-borne disease, red crown rot.
abstract: BACKGROUND
  Within-field multiple crop species intercropping is well documented and used for disease control, but the underlying mechanisms are still unclear. As roots are the primary organ for perceiving signals in the soil from neighboring plants, root behavior may play an important role in soil-borne disease control.
  
  
  RESULTS
  In two years of field experiments, maize/soybean intercropping suppressed the occurrence of soybean red crown rot, a severe soil-borne disease caused by Cylindrocladium parasiticum (C. parasiticum). The suppressive effects decreased with increasing distance between intercropped plants under both low P and high P supply, suggesting that root interactions play a significant role independent of nutrient status. Further detailed quantitative studies revealed that the diversity and intensity of root interactions altered the expression of important soybean PR genes, as well as, the activity of corresponding enzymes in both P treatments. Furthermore, 5 phenolic acids were detected in root exudates of maize/soybean intercropped plants. Among these phenolic acids, cinnamic acid was released in significantly greater concentrations when intercropped maize with soybean compared to either crop grown in monoculture, and this spike in cinnamic acid was found dramatically constrain C. parasiticum growth in vitro.
  
  
  CONCLUSIONS
  To the best of our knowledge, this study is the first report to demonstrate that intercropping with maize can promote resistance in soybean to red crown rot in a root-dependent manner. This supports the point that intercropping may be an efficient ecological strategy to control soil-borne plant disease and should be incorporated in sustainable agricultural management practices.
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.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
authors.forename: Man
authors.initials: M
authors.lastname: Wu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
authors.forename: Ruineng
authors.initials: R
authors.lastname: Xu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
authors.forename: Xiurong
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
authors.forename: Ruqian
authors.initials: R
authors.lastname: Pan
authors.affiliation: Department of Tropical Plants and Soil Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America.
authors.forename: Hye-Ji
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Liao
mesh_terms: D000383:Agriculture; D001203:Ascomycota; D018556:Crops, Agricultural / Q000382:microbiology; D009181:Mycoses / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology*; D012988:Soil Microbiology; D013025:Glycine max / Q000382:microbiology*; D003313:Zea mays / Q000382:microbiology*