Since 2008, Pseudomonas syringae pv. actinidiae virulent strains (Psa-V) have quickly spread across the main areas of kiwifruit (Actinidia deliciosa and A. chinensis) cultivation causing sudden and re-emerging outbreaks of bacterial canker to both species. The disease caused by Psa-V strains is considered worldwide as pandemic. Recently, P. syringae strains (ex Psa-LV, now called PsD) phylogenetically related to Psa-V have been isolated from kiwifruit, but cause only minor damage (i.e. leaf spot) to the host. The different biological significance of these bacterial populations affecting kiwifruit highlights the importance of having a diagnostic method able to detect Psa-V, which is currently solely responsible for the severe damage to the kiwifruit industry. In order to improve the specific molecular detection of Psa-V, a real-time PCR assay has been developed based on EvaGreen chemistry, together with a novel qualitative PCR (PCR-C). Both methods are based on specific primer sets for the hrpW gene of Psa. The real-time PCR and PCR-C were highly specific, detecting down to 50 and 200 fg, respectively, and were applied to a range of organs/tissues of kiwifruit with and without symptoms. These methods are important tools for both sanitary and certification programmes, and will help to avoid the spread of Psa-V and to check possible inoculum sources. In addition to being used as routine tests, they will also enable the study of the biology of Psa-V and the disease that it causes, whilst avoiding the detection of other populations of related P. syringae present in kiwifruit.

Latent mosaic is a widely distributed disease of peach caused by peach latent mosaic viroid (PLMVd). Some strains induce mosaic symptoms on leaves, delay in leaf emergence, flowering and maturity, calico and malformation of fruits with cracked sutures and enlarged pits, bud necrosis and, in more severe cases, early decline of the trees. To prevent the use of infected propagating material, international certification schemes provide for the absence of PLMVd from peach mother plants. Until a few years ago, detection of PLMVd was mainly based on cross‐protection tests on GF305 peach seedlings. Recently, improved knowledge of the PLMVd genome and optimization of molecular techniques applied to the diagnosis of plant pathogens have stimulated studies aimed at setting up diagnostic methods that are sensitive, reliable and less time‐consuming. A comparative trial among different Italian institutions has been set up to compare the sensitivity, specificity and reproducibility of the currently available diagnostic techniques that are routinely applied for the detection of PLMVd in peach germplasm. In this paper, we compare the results obtained in the diagnosis of PLMVd performed with biological indicators and molecular techniques (‘spot‐blot’ and ‘tissue‐blot’ hybridization using a non‐radioactive probe and reverse transcriptase‐polymerase chain reaction) starting from different organs (leaves, buds and bark) collected from infected and healthy peach plants and using two total nucleic acid extraction methods. On the basis of the results obtained, we suggest that a tissue‐blot hybridization assay using a PLMVd cRNA digoxigenin‐labelled probe and starting from bud tissue is a reliable diagnostic method for inclusion in quarantine or certification protocols that require the absence of PLMVd from propagating material of peach.

During recent years; Xylella fastidiosa subsp. pauca (Xfp) has spread in Salento causing relevant damage to the olive groves. Measures to contain the spreading of the pathogen include the monitoring of the areas bordering the so-called “infected” zone and the tree eradication in case of positive detection. In order to provide a control strategy aimed to maintain the tree productivity in the infected areas, we further evaluated the in vitro and in planta mid-term effectiveness of a zinc-copper-citric acid biocomplex. The compound showed an in vitro bactericidal activity and inhibited the biofilm formation in representative strains of X. fastidiosa subspecies, including Xfp isolated in Apulia from olive trees. The field mid-term evaluation of the control strategy assessed by quantitative real-time PCR in 41 trees of two olive groves of the “infected” area revealed a low concentration of Xfp over the seasons upon the regular spraying of the biocomplex over 3 or 4 consecutive years. In particular, the bacterial concentration lowered in July and October with respect to March, after six consecutive treatments. The trend was not affected by the cultivar and it was similar either in the Xfp-sensitive cultivars Ogliarola salentina and Cellina di Nardò or in the Xfp-resistant Leccino. Moreover, the scoring of the number of wilted twigs over the seasons confirmed the trend. The efficacy of the treatment in the management of olive groves subjected to a high pathogen pressure is highlighted by the yielded a good oil production

Xylella fastidiosa subsp. pauca is the causal agent of “olive quick decline syndrome” in Salento (Apulia, Italy). On April 2015, we started interdisciplinary studies to provide a sustainable control strategy for this pathogen that threatens the multi-millennial olive agroecosystem of Salento. Confocal laser scanning microscopy and fluorescence quantification showed that a zinc-copper-citric acid biocomplex—Dentamet®—reached the olive xylem tissue either after the spraying of the canopy or injection into the trunk, demonstrating its effective systemicity. The biocomplex showed in vitro bactericidal activity towards all X. fastidiosa subspecies. A mid-term evaluation of the control strategy performed in some olive groves of Salento indicated that this biocomplex significantly reduced both the symptoms and X. f. subsp. pauca cell concentration within the leaves of the local cultivars Ogliarola salentina and Cellina di Nardò. The treated trees started again to yield. A 1H-NMR metabolomic approach revealed, upon the treatments, a consistent increase in malic acid and γ-aminobutyrate for Ogliarola salentina and Cellina di Nardò trees, respectively. A novel endotherapy technique allowed injection of Dentamet® at low pressure directly into the vascular system of the tree and is currently under study for the promotion of resprouting in severely attacked trees. There are currently more than 700 ha of olive groves in Salento where this strategy is being applied to control X. f. subsp. pauca. These results collectively demonstrate an efficient, simple, low-cost, and environmentally sustainable strategy to control this pathogen in Salento.