Characterization of Pseudomonas ”reactans” isolates associated to cultivated mushrooms

CHARACTERIZATION OF PSEUDOMONAS ”REACTANS” ISOLATES ASSOCIATED TO CULTIVATED MUSHROOMS D. Lamorte, P. Lo Cantore and N. S. Iacobellis Scuola di Scienze Agrarie, Forestali, Alimentari ed Ambientali, 2Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano 10, 85100, Potenza, Italy; E-mail: nicola.iacobellis@unibas.it Pseudomonas “reactans”, considered a saprophyte associated to cultivated mushrooms and used for the identification of P. tolaasii in the white line assay, has been established to be the causal agent of P. eryngii yellowing and to be involved with P. tolaasii and other fluorescent pseudomonads in the development of the brown blotch on A. bisporus and the yellowing of P. ostreatus. The pathogen isolates share the common feature to form white precipitates when grown near P. tolaasii in the “white line” assay and appear to belong to P. fluorescens (biovar III and V) but it is a not yet a classified species. The purposes of this study was to characterise 20 isolates of P. “reactans” for phenotypic and genotypic traits with the final aim to contribute to its characterization and classification. Isolates were evaluated for biochemical, physiological and nutritional features, for the productions of antimicrobial and hemolytic substances, siderophores and volatile organic compounds (VOCs), and for their pathogenicity on A. bisporus. Pseudomonas-selective PCR primer amplification of the16S rDNA gene and amplicon sequences, deposited at EMBL-EBI, indicate the bacterial isolates as belonging to P. fluorescens though some differences have been observed among the isolates. However, further REP-PCR analysis showed the genetic heterogeneity of the bacterium. Further amplification and sequencing of other housekeeping genes is in progress with final aim to assess the genetic relatedness of P. “reactans” isolates.