0000000000903348
AUTHOR
P. Bella
Molecular diagnostic tools for the detection and characterization of Phoma tracheiphila
In the recent years PCR-based techniques for the identification and detection of Phoma tracheiphila, the causal agent of citrus mal secco disease, have been evaluated aiming to provide tools for biological and epidemiological studies. A wide collection of P. tracheiphila strains was used to evaluate and validate diagnostic protocols and a fAFLP method for fungal characterization. Conventional and real-time PCR protocols were successfully tested for the specific identification of P. tracheiphila and its detection in planta. A further improvement of the real-time PCR protocol and the DNA extraction methods allowed the quantification of the fungus both from naturally infected and artificially …
Detection and identification of Xanthomonas arboricola pv. pruni from symptomless plant material: results of an Italian test performance study
Xanthomonas arboricola pv. pruni, the causal agent of bacterial spot disease of stone fruits, is a regulated quarantine pathogen in the European Union, listed as an A2 pest by the European and Mediterranean Plant Protection Organization (EPPO). Because detection and identification of this pathogen is key for its management and to ensure the production of pest free propagation material, it should be based on reliable tests, in particular when dealing with symptomless material. The current EPPO diagnostic Standard (PM 7/64) does not provide specific molecular methods for detection of this pest. The present paper summarizes the results of a test-performance study (TPS) to validate, at a nation…
Pathogenicity and possible biological control of fungi associated to Botryosphaeria dieback of grapevine in Western Sicily
Botryosphaeria dieback is a widespread grapevine trunk disease caused by species of fungi within the family Botryosphaeriaceae. Symptoms of the disease include bud necrosis, leaf chlorosis, vascular discoloration of the wood, cankers and dieback. In 2013 typical symptoms of Botryosphaeria dieback was observed in Western Sicily and four species associated with the syndrome were isolated and identified as Diplodia seriata, Lasiodiplodia mediterranea, Neofusicoccum parvum and Neofusicoccum vitifusiforme. In order to fulfill Koch’s postulates, pathogenicity tests of eighteen isolates were performed on two-year grapevine cuttings of cv. Inzolia. Six months after inoculation all the Botryosphaeri…
Characterization of Alternaria alternata Isolates from Tangerine Hybrids Affected by Brown Spot in Italy
Alternaria brown spot, caused by Alternaria alternata, is the most important disease of tangerines and their hybrids worldwide, including Italy. The disease represents, for some susceptible citrus cultivar, a limiting factor in profitable cultivation. The results of the characterization of A. alternata isolates obtained from lesions on leaves and fruits of Fortune, Nova and Winola hybrids and Valencia sweet orange, collected in two groves located in Calabria and Sicily, is reported. An endopolygalacturonase gene (endoPG) was sequenced from five representative strains and a phylogenetic tree based on endoPG sequence data of Italian isolates and those of citrus associated Alternaria species d…
Preliminary evaluation of a zinc-copper-citric acid biocomplex for the control of Plenodomus tracheiphilus causal agent of citrus mal secco disease
In this study we evaluated a zinc copper-citric acid biocomplex (Dentamet®) for the effect on citrus mal secco disease caused by Plenodomus tracheiphilus. In vitro tests highlighted an inhibitory activity of the compound on mycelial growth and phialoconidia germination. Independent in vivo trials were performed in a growth chamber inoculating a virulent fungal isolate on sour orange seedlings and young plants of two lines of Femminello lemon, namely ‘Zagara bianca’ and ‘2Kr’, grafted on sour orange and grown in pots. The compound was leaf sprayed three days before the inoculation by wounds with phialoconidia. Overall, disease index and disease progress curve in plants inoculated with P. tra…
Evaluation of oleander accessions for resistance to Pseudomonas savastanoi pv. nerii
Nine oleander accessions were evaluated for resistance to Pseudomonas savastanoi pv. nerii, causal agent of the oleander knot disease. None of the accessions was resistant when tested with three bacterial strains of different virulence, but they varied significantly in the severity of symptoms induced by these strains. The most susceptible accessions "Dark Salmon" (dark salmon flower) showed deformation of stems, leaves and seed pods and secondary knots on aerial parts, whereas the least susceptible one "White" (white flower), inoculated with the least virulent strain, showed neither localized knots at the inoculation point nor secondary symptoms. In this study an in vitro test, based on pr…
Efficacy of microbial consortia and natural compounds as seed treatment for tomato pathogen management
In this study the efficacy of experimental treatments based on microbial consortia (MC) (beneficial rhizobacteria and fungi, actinomycetes, arbuscular mycorrhizal fungi) and natural compounds (NCs) (chitosan and glucosinolates) as seed treatments for tomato bacterial and fungal pathogens management (Xanthomonas euvesicatoria pv. perforans, Xep; Pseudomonas syringae pv. tomato, Psto; Fusarium oxysporum f. sp. radicis-lycopersici, FORL) was evaluated. Independent trials were performed by using organic tomato seeds ‘San Marzano nano’. Treatments were performed by soaking seeds either in aqueous MC suspensions or NC dilutions. The direct effect on the seed inoculum was performed on seeds inocul…
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…
Interactions between Bacillus amyloliquefaciens AG1 and Aspergillus spp. contaminating food and feedstuffs
Aspergillus is a widespread fungal genus contaminating and degrading food and feeds mostly during storage. Some species can also produce carcinogenic mycotoxins harmful for human and animal health. In this study, Bacillus amyloliquefaciens AG1 (BaAG1), active against fungal pathogens was evaluated by in vitro tests against seven Aspergillus species belonging to six Aspergillus sections. After 7 days of incubation at 25°C, mycelial growth of all fungal species was reduced from 46.53% to 60.92%, compared to the controls. The inhibitory effect of BaAG1 cell-free culture filtrate was tested by turbidimetric measurements by using ScanReady P-800 that allow the automatic and continuous monitoring…
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…