Biodiversity of Trichoderma strains in Tunisia.

Trichoderma strains were sampled in 4 different bioclimatic zones of Tunisia, a Mediterranean North African country with strong climatic and edaphic variability from north to south, to assess the genetic diversity of endemic species of Trichoderma and their relationship to the bioclimatic zones. In all, 53 strains were isolated and identified at the species level by analysis of their internal transcribed spacers regions 1 and 2 (ITS1 and ITS2) of the rDNA cluster and (or) a fragment of the translation elongation factor 1 (tef1) gene, using an online interactive key for species identification in Trichoderma and ex-type strains and taxonomically established isolates of Trichoderma as references. At least 2 different species were observed in each ecosystem. Trichoderma harzianum clade VI and Trichoderma longibrachiatum were present in forest soils in north Tunisia; Trichoderma atroviride and Trichoderma hamatum were found in cultivated fields in northeast Tunisia; T. harzianum clade VI, a Trichoderma sp. close to the T. harzianum complex, and Trichoderma saturnisporum were isolated from forest soils in central Tunisia; and T. harzianum clade II and T. hamatum were present in oasis soils in south Tunisia.

Biological control of grey mould in strawberry fruits by halophilic bacteria.

AIMS: Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti-Botrytis metabolites and volatiles. METHODS AND RESULTS: Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea. Thirty strains (20.2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20 degrees C, from 50% to 91.66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui, B. subtilis, B. pumilus, B. licheniformis, Terribacillus halophilus, Halomonas elongata, Planococcus rifietoensis, Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites. CONCLUSIONS: Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.