Irene Donati

New insights on the bacterial canker of kiwifruit (Pseudomonas syringae pv. actinidiae)

Since 2008, Pseudomonas syringae pv. actinidiae, the causal agent of bacterial canker of kiwifruit has become the main pathogen of yellow and green fleshed kiwifruit. All major kiwifruit producing countries in the world have been affected by this bacterial pathogen, leading to substantial economic losses. This review presents the current knowledge on various aspects about the origin, epidemiology, detection and control strategies of Pseudomonas syringae pv. actinidiae.

Greenhouse assays on the control of the bacterial canker of kiwifruit (Pseudomonas syringae pv. actinidiae)

BACKGROUND: Pseudomonas syringae pv. actinidiae (Psa) is the etiologic agent of the bacterial canker of kiwifruit, the most severe disease of Actinidia spp. This pathogen was firstly recorded in Japan and in China. The initial occurrence in Italy dates back to 1992, but the most important outbreak was in 2008. From that year, Psa has spread worldwide with a devastating virulence causing substantial losses to kiwifruit production in China, Italy, New Zealand, Chile, France and Portugal. OBJECTIVE: Screening the existing compounds with different mode of action for their efficacy in controlling Psa on Actinidia deliciosa (cv. Hayward) grown in controlled conditions. METHODS: Products were grouped according to their active ingredients and mode of action in the following categories: Copper compounds, plant extracts, disinfectants, resistance inducers, filming agents and biological control agents (BCAs). The experiments were performed on potted A. deliciosa (cv Hayward) vines grown in controlled greenhouse conditions. Inoculation was experimentally performed by spraying each plant till run off with a suspension of a highly virulent, biovar 3 Psa strain. Disease control and phytotoxicity were monitored for 15 and 30 days after inoculation. RESULTS: Copper compounds and resistance inducers (acibenzolar-S-methyl, Fosetyl-Al) showed the most promising results. However, few other compounds, such as some plant extracts and disinfectants (Verdeviva), provided some protection. Also biological control agents (BCAs), containing living microorganisms, partially controlled the disease. CONCLUSION: Copper compounds and resistance inducers can be possibly combined to develop a more robust and effective control strategy in open field. In addition, BCAs seem interesting, particularly in specific phenological stages when other control methods cannot be used, although results require further validation.

Design and implementation of a multi sensors self sustainable wearable device

Wearable electronics is increasingly attracting researchers and manufacturers for the application opportunities it opens. Chip makers are responding to the hot wearable-computer trend with new components, microcontrollers and sensors. The most critical challenge is the autonomy of the systems. Even if battery management can help in extending the lifetime, the trade-off between features given by a multisensory platforms and autonomy can determine if a platform will win or not in the marketplace. In this paper we present a bracelet device, which attempts to maximize the capability of sensors on board, while still keeping the energy consumption low. Aggressive power management and an accurate selection of the sensors are addressed in this paper to demonstrate the effectiveness of our design.

First Report of Pseudomonas syringae pv. actinidiae on Kiwifruit Pollen from Argentina

During last years, in Mar del Plata (Argentina) area, many kiwifruit orchards composed by only male plants (Actinidia deliciosa cv. Chieftain) have been established for pollen production and commercialization, since the country was considered unaffected by Psa. When mature, the anthers are detached and dried, and grains of pollen collected with a portable cyclonic pollen collector. Then, routine controls aimed to assess the risk of infection by Pseudomonas syringae pv. actinidiae (Psa), the causal agent of kiwifruit bacterial canker (Takikawa et al., 1989), are carried out by plating 1 gram aliquots of pollen on semi-selective medium (modified KB) and incubating plates for 48-72 h at 27 °C. During one of these controls, in February 2015, some bacterial colonies with morphological features similar to Psa were detected. After purification, four of them (labeled as Arg1.1 to Arg2.3) were found to be gram negative, non-fluorescent, positive for levan production, and caused hypersensitive response on tobacco. ...

Insecticidal Activity of Photorhabdus luminescens against Drosophila suzukii

Drosophila suzukii causes considerable economic damage to small and thin-skinned fruits including cherry, blueberry, raspberry, grape and strawberry. Since it attacks fruits at the ripening stage, the use of chemical pesticides is limited due to the high risk of residues on fruit. Biological control is thus expected to play an essential role in managing this pest. The Gram-negative bacterium, Photorhabdus luminescens and its symbiotic Heterorhabditis spp. nematode have been shown to be highly pathogenic to insects, with a potential for replacing pesticides to suppress several pests. Insecticidal activity of P. luminescens at different bacterial cell concentrations and its cell-free supernatant were assessed against third-instar larvae and pupae of D. suzukii under laboratory conditions. P. luminescens suspensions had a significant oral and contact toxicity on D. suzukii larvae and pupae, with mortalities up to of 70–100% 10 days after treatment. Cell-free supernatant in the diet also doubled mortality rates of feeding larvae. Our results suggest that P. luminescens may be a promising candidate for biological control of D. suzukii, and its use in integrated pest management (IPM) programs is discussed.

Pathways of flower infection and pollen-mediated dispersion of Pseudomonas syringae pv. actinidiae, the causal agent of kiwifruit bacterial canker

Flowers can provide a protected and nutrient-rich environment to the epiphytic microflora, thus representing a sensible entry point for pathogens such as Pseudomonas syringae pv. actinidiae (Psa). This bacterium can colonize both male and female Actinidia flowers, causing flower browning and fall, and systemic invasion of the host plant, eventually leading to its death. However, the process of flower colonization and penetration into the host tissues has not yet been fully elucidated. In addition, the presence of Psa in the pollen from infected flowers, and the role of pollination in the spread of Psa requires confirmation.The present study employed a Psa strain constitutively expressing the fluorescent GFPuv protein, to visualize in vivo flower colonization. Microscopy observations were performed by means of confocal laser scanning and wide-field fluorescent microscopy, and were coupled with the study of Psa population dynamics by quantitative PCR (q-PCR). The pathogen was shown to colonize stigmata, move along the stylar furrow, and penetrate the receptacles via the style or nectarhodes. Once the receptacle was invaded, the pathogen migrated along the flower pedicel and became systemic. Psa was also able to colonize the anthers epiphytically and endophytically. Infected male flowers produced contaminated pollen, which could transmit Psa to healthy plants. Finally, pollinators (Apis mellifera and Bombus terrestris) were studied in natural conditions, showing that, although they can be contaminated with Psa, the pathogen’s transmission via pollinators is contrasted by its short survival in the hive.Kiwi fruit: Insights to combat bacterial cankerStudying the transmission pathways of a bacterium that infects and kills kiwi fruit plants suggests that modified plant protection strategies could minimize the risk of disease. Researchers in Italy and New Zealand, led by Francesco Spinelli at the University of Bologna, investigated Pseudomonas syringae pv. Actinidiae (Psa), which causes kiwi fruit bacterial canker. This has been a major problem worldwide since a pandemic outbreak in 2008. The results show that flower tissues, especially the stigmata which receive transmitted pollen, are crucial sites allowing Psa to grow and penetrate into the plants. Evidence is presented of bacterial transmission via the pollen dispersed from plants that do not themselves show signs of infection. Suggested new control strategies include inspecting and treating pollen-donating plants, and using biological agents to compete with Psa growing inside kiwi fruit flowers.

Optimization of cultural practices to reduce the development of Pseudomonas syringae pv. actinidiae, causal agent of the bacterial canker of kiwifruit

BACKGROUND: The bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae (Psa), affects several cultivated Actinidia species, including A. chinensis and A. deliciosa. Its development is related to permissive environmental conditions, such as temperature, humidity, presence of entry points, genetic and physiological features of the host plant. Moreover, also cultural practices influence, directly or indirectly, the disease development. OBJECTIVE: The role of agricultural practices on disease development and spread was studied. METHODS: Irrigation, pruning and training systems were tested in the field according to conventional orchard management. Experiments on mineral nutrition, use of bio-regulators and rootstock susceptibility were performed in controlled conditions. Bacterial growth, symptom development and disease incidence were assessed in relation to the different practices. RESULTS: High nitrogen fertilization, iron deficiency and water stress were related to more severe symptoms. Open canopies allow a better irradiation, aeration, and penetration of phytosanitary treatments. Synthetic gibberellins reduced disease incidence and severity in controlled conditions. Fruits from diseased plants showed a lower quality and storability. CONCLUSIONS: Dense canopies are harder to manage and more exposed to bacterial canker. Pruning tools and irrigation water are relevant for the bacterial spread.