Changes in the bacterial community of Canary island date palm tissues attacked by Rhynchophorus ferrugineus (Coleoptera: Curculionidae).

The red palm weevil (RPW), Rhynchophorus ferrugineus is a trunk tissue borer that has recently become the major pest of palms in the Mediterranean Basin. In Sicily the red palm weevil is strongly associated with the Canary island date palm, Phoenix canariensis Hortorum ex Chabaud, an ornamental palm with high economic value. RPW larvae consumes the trunk tender soft tissues, making galleries that present a chewed appearance with a characteristic fermented odour. Several aspects of the RPW’s biology still need to be investigated such as its gut bacterial community, and the agents of fermentation processes that occur in the galleries made by the larvae. The aim of this work was to analyse the bacterial community in the tissues of Canary island date palm attacked by RPW. Healthy and attacked palm tissue samples were aseptically ground and serially diluted for bacterial counts and isolation on Nutrient Agar and Tryptone-yeast extract agar. Bacterial counts revealed higher microbial biomass in attacked wood. Phenotypically different colonies were picked in triplicate and grouped into Operational Taxonomic Units (OTU) by analysis of the ribosomal internal transcribed spacer (ITS) polymorphisms. A dramatic decline in biodiversity was observed in the bacterial community of the attacked tissues. Partial sequencing of 16S rRNA gene of representative isolates of each OTU and BLASTn search results revealed that the majority of isolates from infested tissue are facultative anaerobes with fermentative metabolism and aerotollerant fermenting anaerobes. Interestingly, entomopathogenic bacteria of the Bacillus thuringiensis/ B.cereus group were also detected in both health and attacked tissues.