Search

Pseudomonas syringae pv. actinidiae is an important pathogen of kiwifruit (Actinidia deliciosa), and bacterial canker of this host is managed by monitoring and chemical control strategies. The efficacy of the bio-pesticides Amylo-X (R) (based on Bacillus amyloliquefaciens subsp. plantarum strain D747) and Serenade Max (R) (strain QST713 of B. subtilis) was evaluated by in vitro and in vivo experiments. Both antagonists inhibited different biovars of the pathogen in in vitro assays; QST713 was more efficient than D747. The two Bacillus strains also colonized A. deliciosa flowers (c. 10(5-7) cfu per flower) up to 96 h after inoculation. 1)747 persisted on leaves (c. 10(4-6) cfu cm(-2)) up to 4 weeks after inoculation, during 2 years in Emilia Romagna and Latium regions of Italy. On flowers, the antagonists reduced pathogen populations, compared to untreated (control) flowers. On A. deliciosa and A. chinensis plants under controlled conditions, Amylo-X (R) reduced severity of bacterial canker, providing ca. 50% relative protection on A. deliciosa and 70% on A. chinensis. Serenade Max (R) was less effective, giving 0% relative protection on A. deliciosa and 40% on A. chinensis. In a field trial, on A. deliciosa plants, Amylo-X (R) reduced the severity of bacterial canker on leaves, providing ca. 40% relative protection. The sensitivity of both antagonistic strains to streptomycin sulphate was confirmed by testing the most used concentration where antibiotics are approved for management of bacterial pathogens.

A study was conducted on 14 accessions of Actinidia spp. to evaluate their susceptibility to the bacterial canker. Experimental inoculations were carried out, under controlled conditions, on young leaves of kiwifruit plants grown in pots by spraying a calibrated water suspension of an Italian, virulent strain (isolated in 2013) of Pseudomonas syringae pv. actinidiae. Actinidia chinensis ‘Belen’ was used as positive control, being a known susceptible genotype. Plants inoculated with sterile distilled water and non-inoculated ones were used as negative control. The disease assessments were performed 21 days after inoculation with the pathogen. The disease severity (mean of leaf spots per treatment) allowed to detect one A. chinensis selection showing low susceptibility, comparable to that of selections belonging to A. arguta, A. hemsleyana and A. eriantha species, that showed a very low susceptibility. No selection was found more susceptible than ‘Belen’, but among all selections, one resulted comparable with it. Eight selections were found to be moderately susceptible, and three of them (A. chinensis selections) were less susceptible than A. deliciosa ‘Hayward’, that is known having an intermediate susceptibility.

Plant bacterial diseases are routinely managed with scheduled treatments based on heavy metal compounds or on antibiotics; to reduce the negative environmental impact due to the use of such chemical compounds, as pollution or selection of antibiotic resistant pathogens, the integrated control management is required. In the frame of a sustainable agriculture the use of bacterial antagonists, biological agents, plant defence response elicitors or resistant host plant genotypes are the most effective approaches. In this work, cold atmospheric pressure plasma (CAP) was applied to sterile distilled water, inducing the production of a hydrogen peroxide, nitrite and nitrate, and a pH reduction. In particular, an atmospheric pressure dielectric barrier discharge (DBD) has been used to produce plasma activated water (PAW), that was firstly assayed in in vitro experiments and then in planta through application at the root apparatus of tomato plants, against Xanthomonas vesicatoria (Xv), the etiological agent of bacterial leaf spot. Moreover, the transcription abundance of five genes related to the plant defense was investigated in response to PAW treatment. PAW did not show direct antimicrobial activity against Xv in in vitro experiments, but it enhanced the tomato plants defenses. It was effective in reducing the disease severity by giving relative protections of ca. 61, 51 and 38% when applied 1 h, 24 h and 6 days before the experimental inoculation, respectively. In addition, the experiments highlighted the pal gene involvement in response to the PAW treatments and against the pathogen; its transcription levels resulted significantly high from 1 to 48 h until their decrease 192 h after PAW application.

Structured AbstractObjectives To investigate possible changes and/or device-related impairments in phonetic habits produced by rapid maxillary expansion (RME). Materials and Methods Thirty-five patients scheduled for RME were divided into two groups: Group A (banded two-arm Hyrax) and Group B (banded four-arm Hyrax). Speech samples were collected at six time points, before, during and after RME removal. Acoustical analysis was performed using PRAAT and BioVoice analysis tools. Ten volunteers completed a questionnaire on the acceptability of patient's speech. Maxillary dimensions and palatal volume were measured on dental casts before and after expansion using a digital gauge. Results Voice analysis showed an increase in the peak frequency of fricative consonants (/s/,/ʃ/) after expansion, whereas there was no change of formant frequencies of palatal consonants (/ɲ/,/ʎ/). Vowel /i/ displayed a lowering of the first formant frequency, and an increase in the second and third formant frequencies. After bonding, Group B showed both a greater reduction in the peak frequency of fricatives and a greater increase in the formant frequencies of palatal consonants than Group A. Conclusion Rapid maxillary expansion causes a slight phonetic change in the acoustical parameters of both consonants and vowels. The two-arm Hyrax caused less speech impairment than the four-arm Hyrax during the treatment.

Specific VOC emissions from infected plants allow their recognition and elicit defence responses in neighboring plants, which are, however, insufficient to induce resistance. A wide range of volatile organic compounds (VOCs) is released during plant–pathogen interactions both by the pathogens and the hosts. Some of these VOCs are specific for the different diseases and are known to play a role in the pathogenicity or in plant defence responses. Besides, disease-specific VOCs may serve as markers for diagnostic protocols, which allow a non-destructive and rapid screening of bulk samples of plant material. This work aimed to verify the feasibility of a VOC-based diagnosis and to investigate the possible biological role of VOCs released during the plant–pathogen interactions. The volatile emissions from Pseudomonas syringae pv. actinidiae in axenic cultures and from inoculated in vitro kiwifruit plants were characterized by gas chromatography–mass spectrometry (GC–MS) and proton transfer reaction–time-of-flight-mass spectrometry (PTR–ToF-MS). By GC–MS, several putative biochemical markers, such as 1-undecene, were identified. PTR–ToF-MS resulted highly effective in screening the plant material for latent infections. To develop a more user-friendly, portable and less expensive diagnosis system, two different electronic nose models were tested for the early diagnosis of P. syringae pv. actinidiae in asymptomatic plant material. Our experiments demonstrated the feasibility of the electronic nose-based screening of infected plant material. Concerning the biological role of the VOCs released during the plant–pathogen interactions, the exposure of healthy plants to VOCs from infected ones influences the plant growth and induces the stimulation of protective responses. However, after the infection, P. syringae pv. actinidiae is able to selectively inactivate the induced plant defences.

Italy is one of the largest producers of Kiwi [Actinidia deliciosa (Chev.) Liang & Ferguson] and cv. Hayward is the most widespread. Over the past 10 years, especially in Northeastern and Central Italy, there was an increase in the cultivation of yellow kiwi (Actinidia chinensis Planchon) in which symptoms of bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) have been reported in cultivations in the Lazio region. In Japan, China and Korea, major economic losses were caused by this bacterial disease that seriously damages all vegetative organs of the plant. The development of reliable diagnostic methods for asymptomatic materials is crucial for the activity of Plant Protection Services in order to confirm the presence of the pathogen in the territory and in marketing materials. Bacteria isolation from the fruits surface (31 samples cv. Hayward from Emilia Romagna region) and from their asymptomatic columellae to detect the presence of Psa was performed. As for the bacteria identification the following tests were carried out: fluorescent pigment production, HR in tobacco leaves, oxidase activity, acid production from sugars and molecular analysis (PCR-RFLP, REP-, BOX-PCR and Bio-PCR). The identification assays of the isolates obtained from the surface and columella fruits of all samples were negative for Psa. In order to discriminate Psa from the other kiwifruit pathogenic bacteria (i.e. Pseudomonas syringae pv. syringae and Pseudomonas viridiflava) and to confirm the isolates identification, the Psa pathogenicity was tested in fruits and kiwifruit plantlets. Moreover, Psa lives in the phyllosphere together with non-pathogenic bacteria that may interfere in the diagnosis of the bacterial canker by means of false negative or positive results. Therefore, from leaves and shoots of asymptomatic plants of Actinidia chinensis Hort 16A and Actinidia deliciosa cv. Hayward, collected from the Emilia Romagna region, epiphytic bacteria were isolated and studied.

Aims To analyse genetic diversity and epidemiological relationships among 54 strains of Allorhizobium vitis isolated in Europe during an 8-year period and to assess the relative contribution of mutation and recombination in shaping their diversity. Methods and Results By using random amplified polymorphic DNA (RAPD) PCR, strains studied were distributed into 12 genetic groups. Sequence analysis of dnaK, gyrB and recA housekeeping genes was employed to characterize a representative subcollection of 28 strains. A total of 15 different haplotypes were found. Nucleotide sequence analysis suggested the presence of recombination events in A. vitis, particularly affecting dnaK locus. Although prevalence of mutation over recombination was found, impact of recombination was about two times greater than mutation in the evolution of the housekeeping genes analysed. Conclusions The RAPD analysis indicated high degree of genetic diversity among the strains. However, the most abundant RAPD group was composed of 35 strains, which could lead to the conclusion that they share a common origin and were distributed by the movement of infected grapevine planting material as a most common way of crossing long distances. Furthermore, it seems that recombination is acting as an important driving force in the evolution of A. vitis. As no substantial evidence of recombination was detected within recA gene fragment, this phylogenetic marker could be reliable to characterize phylogenetic relationships among A. vitis strains. Significance and Impact of the Study We demonstrated clear epidemiological relationship between majority of strains studied, suggesting a need for more stringent phytosanitary measures in international trade. Moreover, this is the first study to report recombination in A. vitis.

Studies were carried out in 2002 and 2003 to evaluate the suitability of the highly efficient pollinator of pear Osmia cornuta (Hymenoptera Megachilidae) as a carrier of a rifampicin resistant mutant of the Bacillus subtilis strain BS-F4 (BS-F4rif) on pear flowers cultiver 'Abbé Fétel' for the biological control of fire blight, and its capacity was compared with that of Apis mellifera. A dispenser for the spread of bacteria by O. cornuta was successfully developed. Females exited and entered the dispenser through the proper pathways 81.4% and 97.7% of the attempts, respectively, and the number of BS-F4rif reisolated from the body of O. cornuta exiting the dispenser ranged from 104 to 107 CFU/insect. Individuals of A. mellifera carried an average population of 104 CFU/insect. In net screened tunnel conditions, the efficiency of O. cornuta to carry and deposit the BS-F4rif on pear flowers during a single visit was higher than that of A. mellifera. Both in 2002 and 2003, the dispersal ability of bees was assessed in a 7 ha pear orchard. Trees were labelled at 2, 10, 50, 110 m from the nesting shelter, in the direction of the four cardinal points. Flowers on branches covered with fine netting acted as controls. Mason bees distributed 30 g of the biocontrol agent (BCA). Fifty flowers from both exposed and netted branches were sampled at 3, 7 and 10 days (the latter only in 2003) after the beginning of distribution. BS-F4rif was not recovered from any of the flowers on net-covered branches, whereas the bacterium was consistently recovered on the flowers of non-screened plants. Variation in distribution and population density of the BCA among flowers were observed, with greater colonisation in 2002 than 2003. We conclude that O. cornuta may serve as a carrier for the dispersal of powdered BCA formulations to pear flowers.

The definition of vegetation types at different hierarchical levels, both to study the vegetation processes and for practical cartography representation, is still considered a critical issue in many circles of plant ecologists. The problems are mainly related to the misleading idea that classification of the vegetation system, as developed by European phytosociologist during the last century within the discipline called syntaxonomy, would imply the assumption of the organismic concept of the plant community. After a short discussion on the role of Braun- Blanquet approach in plant ecology and in landscape ecology, the methods to detect multispecies responses along environmental gradients are briefly reviewed. In the main part of this article, we intend to stress that concepts considered critical, such as plant association and its ecological niche, are just operational tools that have nothing to do with the individualistic or organismic interpretation of plant communities in vegetation studies. Important to our views on vegetation, we believe that plant associations as well as the higher sintaxa can be regarded as fuzzy sets in an operational context for describing vegetation along ecological gradients in synthetic ways and can further the understanding of vegetation variation.