title: Quantification and role of organic acids in cucumber root exudates in Trichoderma harzianum T-E5 colonization.
abstract: The ability to colonize on plant roots is recognized as one of the most important characteristics of the beneficial fungi Trichoderma spp. The aim of this study is to prove that the utilization of organic acids is a major trait of Trichoderma harzianum T-E5 for colonization of cucumber roots. A series experiments in split-root hydroponic system and in vitro were designed to demonstrate the association between the utilization of organic acids and T-E5 colonization on cucumber roots. In the split-root hydroponic system, inoculation with T-E5 (T) significantly increased the biomass of cucumber plants compared with CK (non-inoculation with T-E5). The T-E5 hyphae densely covering the cucumber root surface were observed by scanning electron microscopy (SEM). Three organic acids (oxalic acid, malic acid and citric acid) were identified from both the CK and T treatments by HPLC and LC/ESI-MS procedures. The amounts of oxalic acid and malic acid in T were significantly higher than those in CK. All the organic acids exhibited different and significant stimulation effects on the mycelial growth and conidial germination of T-E5 in vitro. An additional hydroponic experiment demonstrated the positive effects of organic acids on the T-E5 colonization of cucumber roots. In conclusion, the present study revealed that certain organic acids could be used as nutritional sources for Trichoderma harzianum T-E5 to reinforce its population on cucumber roots.
authors.affiliation: National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Fengge
authors.initials: F
authors.lastname: Zhang
authors.affiliation: National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Meng
authors.affiliation: National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing 210095, PR China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Xingming
authors.initials: X
authors.lastname: Yang
authors.affiliation: National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing 210095, PR China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing 210095, PR China. Electronic address: wei-ran@hotmail.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Ran
authors.affiliation: National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing 210095, PR China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
mesh_terms: D000144:Acids, Acyclic / Q000378:metabolism*; D018553:Cucumis sativus / Q000378:metabolism*; D025282:Mycelium / Q000254:growth & development*; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology*; D014242:Trichoderma / Q000254:growth & development*
chemical_list: D000144:Acids, Acyclic
keywords: Colonization; HPLC; Nutritional source; Organic acids; Split-root hydroponic system