title: Fungal antagonists of the plant pathogen Rhizoctonia solani: selection, control efficacy and influence on the indigenous microbial community.
abstract: A broad spectrum of fungal antagonists was evaluated as potential biocontrol agents (BCAs) against the soil-borne pathogen Rhizoctonia solani using a new combination of in vitro and in vivo assays. The in vitro characterisation of diverse parameters including the ability to parasitise mycelium and to inhibit the germination of Rhizoctonia sclerotia at different temperatures resulted in the selection of six potential fungal antagonists. These were genotypically characterised by their BOX-PCR fingerprints, and identified as Trichoderma reesei and T. viride by partial 18S rDNA sequencing. When potato sprouts were treated with Trichoderma, all isolates significantly reduced the incidence of Rhizoctonia symptoms. Evaluated under growth chamber conditions, the selected Trichoderma isolates either partly or completely controlled the dry mass loss of lettuce caused by R. solani. Furthermore, the antagonistic Trichoderma strains were active under field conditions. To analyse the effect of Trichoderma treatment on indigenous root-associated microbial communities, we performed a DNA-dependent SSCP (Single-Strand Conformation Polymorphism) analysis of 16S rDNA/ITS sequences. In this first assessment study for Trichoderma it was shown that the pathogen and the vegetation time had much more influence on the composition of the microbiota than the BCA treatment. After evaluation of all results, three Trichoderma strains originally isolated from Rhizoctonia sclerotia were selected as promising BCAs.
authors.affiliation: Institute of Vegetable and Ornamental Crops (IGZ) Grossbeeren/Erfurt e.V., Echtermeyer Weg 1, D-14979 Grossbeeren, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Grosch
authors.forename: Katja
authors.initials: K
authors.lastname: Scherwinski
authors.forename: Jana
authors.initials: J
authors.lastname: Lottmann
authors.forename: Gabriele
authors.initials: G
authors.lastname: Berg
mesh_terms: D001483:Base Sequence; D016000:Cluster Analysis; D016172:DNA Fingerprinting / Q000379:methods; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D018545:Lactuca; D008969:Molecular Sequence Data; D010572:Pest Control, Biological / Q000379:methods*; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012337:RNA, Ribosomal, 18S / Q000737:chemistry / Q000235:genetics; D012232:Rhizoctonia / Q000254:growth & development*; D016415:Sequence Alignment; D011198:Solanum tuberosum; D018709:Statistics, Nonparametric; D014242:Trichoderma / Q000235:genetics / Q000254:growth & development*
chemical_list: D004271:DNA, Fungal; D012337:RNA, Ribosomal, 18S