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 …

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…

Defense-related gene expression in two olive cultivars inoculated with Pseudomonas savastanoi pv. savastanoi

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…

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…