Mixed infection of Pectobacterium carotovorum subsp. Carotovorum and P. carotovorum subsp. Brasiliensis in tomato stem rot in Italy

Grafted tomato plants grown in a soilless culture system in heated greenhouses in Sicily were affected by stem rot disease. Symptoms consisted of dark brown longitudinal discoloration of the basal part of the stem and petioles. Longitudinal sections of the stem revealed brown watersoaked or soft-rotted pith tissue and internal vascular discoloration. Bacterial isolates with two different colony morphologies were obtained from symptomatic tissues. Isolates were identified as Pectobacterium spp. on the basis of biochemical and molecular analyses. The analysis of the 16S rRNA gene sequence and of the concatenated sequences of the housekeeping genes rpoS and pgi revealed that the isolates of th…

Unusual occurrence of Schizophyllum comune on young topgrafted citrus

Occurrence of the T36 Genotype of Citrus tristeza virus in Citrus Orchards in Sicily, Italy

Recent phylogenetic studies have shown that different lineages representing mild and virulent Citrus tristeza virus (CTV) isolates have been present in Italy for a long time. The genetic structure of CTV population, based on p23 and p27 genes sequences, highlighted two main clusters referred to as T30 and VT-like, as confirmed by the full genomes sequences of two representative isolates SG29 (KC748392) and Bau282 (KC748391) (Licciardello et al. 2015). On the basis of risk analyses, regulatory measures have been outlined, including the recommendation to replace sour orange (C. aurantium) with tolerant rootstocks and to monitor the spread and the presence (if any) of different isolates not co…

Quantitative detection of pseudomonas corrugata and pseudomonas mediterranea in tomato plants by duplex real-time PCR

Pseudomonas corrugata and P. mediterranea are two closely related bacterial species both causal agents of tomato pith necrosis. To screen tomato planting material reliably, a quantitative real-time PCR assay was developed, to detect and/or discriminate both bacterial pathogens in a single tube. So, two species-specific primer/probe sets were designed on the sequences of two DNA fragments amplified by a previously reported specific PCR protocol. TaqMan real-time PCR assays were developed for individual (simplex PCR) and simultaneous (duplex PCR) amplifications. The assays were performed with the SmartCycler TD II System (Cepheid) and the fluorescence from both FAM and Texas Red channels were…

Pseudomonas corrugata crpCDE is part of the cyclic lipopeptide corpeptin biosynthetic gene cluster and is involved in bacterial virulence in tomato and in hypersensitive response in Nicotiana benthamiana

Summary: Pseudomonas corrugataCFBP 5454 produces two kinds of cyclic lipopeptides (CLPs), cormycin A and corpeptins, both of which possess surfactant, antimicrobial and phytotoxic activities. In this study, we identified genes coding for a putative non-ribosomal peptide synthetase and an ABC-type transport system involved in corpeptin production. These genes belong to the same transcriptional unit, designated crpCDE. The genetic organization of this locus is highly similar to other PseudomonasCLP biosynthetic clusters. Matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) analysis revealed that transporter and synthetase genomic knock-out mutants were u…

CHARACTERIZATION OF ATYPICAL CLAVIBACTER MICHIGANENSIS subsp. MICHIGANENSIS POPULATIONS IN GREENHOUSE TOMATOES IN ITALY

The quarantine bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) is the agent of tomato bacterial canker (TBC), one of the most destructive bacterial diseases of this crop, that causes severe economic losses worldwide. During a recent outbreak of TBC in Sicily (insular Italy), it was impossible to amplify the pat-1 gene by PCR with CMM5/CMM6 primers from affected greenhouse-grown plants from three farms, although Cmm-like colonies were consistently isolated. Microlog metabolic profile, 16S rDNA sequencing and the positive amplification of other Cmm DNA targets supported the identification of the strains as Cmm, suggesting the occurrence of a population lacking the virulence gen…