Isolation and characterisation of a new antagonistic Burkholderia strain from the rhizosphere of healthy tomato plants.

A new Burkholderia strain (PVFi5A) which exhibits antagonism towards many bacterial and fungal plant pathogens has been partially characterised. This strain was isolated from the rhizosphere of tomato plants and was referred to the Burkholderia cepacia complex on the basis of cultural, morphological and biochemical characteristics, including determination of the 16S ribosomal DNA sequence and fatty acid profile. Strain PVFi5A is a Gram-negative, aerobic bacterium, oxidase- and catalase-positive, motile with a polar tuft of flagella, able to grow on a variety of media without producing diffusible pigments; it is avirulent to onion, able to grow at 41 degrees C and resistant to several antibiotic substances. Its fatty acid profile contains the hydroxy acids 18:1 20H, 14:0 3OH and 16:0 3OH, but not the hydroxy acids 16:0 2OH. The antagonistic activity of strain PVFi5A is due to its production of various, as yet unidentified, antimicrobial compounds, one or more of which may differ from those reported previously for certain 'B. cepacia' strains. The ability of PVFi5A to suppress the growth of important bacterial and fungal phytopathogens makes this strain a potential biocontrol agent.

Fluctuation of endophytic bacteria and phytoplasmosis in elm trees.

A total of 658 heterotrophic bacterial colonies isolated from phloem tissues of roots and branches in four months (April, June, September and December) from two elm plants, one of which affected by phytoplasmosis, were typed by means of ARDRA. This analysis revealed the existence of a high degree of variability within the community and was able to detect 84 different ARDRA groups. The Analysis of Molecular Variance was applied to ARDRA patterns to analyze the differentiation between communities isolated from the various samplings. Data obtained were compared with those from a previous work (Mocali et al. 2003). Results indicated that plants with symptoms of phytoplasmosis showed marked alterations in the extent of the fluctuations of the community along the seasons in the different plant organs.

PCR-based assay for the detection of Curtobacterium flaccumfaciens pv. flaccumfaciens in bean seeds.

AIMS: To develop a PCR-based protocol for the rapid, sensitive and specific detection of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) in bean seeds. METHODS AND RESULTS: A pair of PCR primers (CffFOR2-CffREV4), targeting the sequence of a cloned DNA fragment of 550 bp amplified in Repetitive-sequence-based-PCR (Rep-PCR) experiments, were designed and shown to specifically amplify a 306-bp DNA fragment using Cff DNA as template. Moreover, this PCR protocol was demonstrated to successfully detect Cff in naturally infected bean seeds in 36 h. CONCLUSIONS: A specific, highly sensitive and rapid PCR assay for the detection of Cff was achieved. SIGNIFICANCE AND IMPACT OF THE STUDY: Cff is a seed-borne bacterium on the EPPO A2 quarantine list; this procedure may be useful for routine diagnosis of Cff, overcoming the problems of conventional techniques.