Scortichini M.,Cra Research Center For Fruit Trees |
Marcelletti S.,Cra Research Center For Fruit Trees |
Ferrante P.,Cra Research Center For Fruit Trees |
Petriccione M.,Cra Research Unit For Fruit Trees |
Firrao G.,University of Udine
Molecular Plant Pathology | Year: 2012
Pseudomonas syringae pv. actinidiae is the causal agent of bacterial canker of green-fleshed kiwifruit (Actinidia deliciosa) and yellow-fleshed kiwifruit (A.chinensis). A recent, sudden, re-emerging wave of this disease has occurred, almost contemporaneously, in all of the main areas of kiwifruit production in the world, suggesting that it can be considered as a pandemic disease. Recent in-depth genetic studies performed on P.syringae pv. actinidiae strains have revealed that this pathovar is composed of four genetically different populations which, to different extents, can infect crops of the genus Actinidia worldwide. Genome comparisons of these strains have revealed that this pathovar can gain and lose the phaseolotoxin gene cluster, as well as mobile genetic elements, such as plasmids and putative prophages, and that it can modify the repertoire of the effector gene arrays. In addition, the strains currently causing worldwide severe economic losses display an extensive set of genes related to the ecological fitness of the bacterium inplanta, such as copper and antibiotic resistance genes, multiple siderophore genes and genes involved in the degradation of lignin derivatives and other phenolics. This pathogen can therefore easily colonize hosts throughout the year. Taxonomy: Bacteria; Proteobacteria, gamma subdivision; Order Pseudomonadales; Family Pseudomonadaceae; Genus Pseudomonas; Pseudomonas syringae species complex, genomospecies 8; Pathovar actinidiae. Microbiological properties: Gram-negative, aerobic, motile, rod-shaped, polar flagella, oxidase-negative, arginine dihydrolase-negative, DNA 58.5-58.8mol.% GC, elicits the hypersensitive response on tobacco leaves. Host range: Primarily studied as the causal agent of bacterial canker of green-fleshed kiwifruit (Actinidia deliciosa), it has also been isolated from yellow-fleshed kiwifruit (A.chinensis). In both species, it causes severe economic losses worldwide. It has also been isolated from wild A.arguta and A.kolomikta. Disease symptoms: In green-fleshed and yellow-fleshed kiwifruits, the symptoms include brown-black leaf spots often surrounded by a chlorotic margin, blossom necrosis, extensive twig die-back, reddening of the lenticels, extensive cankers along the main trunk and leader, and bleeding cankers on the trunk and the leader with a whitish to orange ooze. Epidemiology: Pseudomonas syringae pv. actinidiae can effectively colonize its host plants throughout the year. Bacterial exudates can disperse a large amount of inoculum within and between orchards. In the spring, temperatures ranging from 12 to 18°C, together with humid conditions, can greatly favour the multiplication of the bacterium, allowing it to systemically move from the leaf to the young shoots. During the summer, very high temperatures can reduce the multiplication and dispersal of the bacterium. Some agronomical techniques, as well as frost, wind, rain and hail storms, can contribute to further spreading. Disease control: An integrated approach that takes into consideration precise scheduled spray treatments with effective and environmentally friendly bactericides and equilibrated plant nutrition, coupled with preventive measures aimed at drastically reducing the bacterial inoculum, currently seems to be the possible best solution for coexistence with the disease. The development of resistant cultivars and pollinators, effective biocontrol agents, including bacteriophages, and compounds that induce the systemic activation of plant defence mechanisms is in progress. Useful websites: Up-to-date information on bacterial canker research progress and on the spread of the disease in New Zealand can be found at: Daily information on the spread of the disease and on the research being performed worldwide can be found at: http://www.freshplaza.it. © 2012 The Authors. Molecular Plant Pathology © 2012 BSPP And Blackwell Publishing Ltd.
Panzella L.,University of Naples Federico II |
Petriccione M.,Cra Research Unit For Fruit Trees |
Rega P.,Cra Research Unit For Fruit Trees |
Scortichini M.,Cra Research Unit For Fruit Trees |
Napolitano A.,University of Naples Federico II
Food Chemistry | Year: 2013
Few literature data are available on the nutraceutical properties of little widespread local apple cultivars. Such lack of information prevents exploitation of these germplasms for genetic improvement of new cultivars and for the re-evaluation of local agricultural products, which may attract a large share of consumers oriented towards natural food evoking ancient flavours. In this work eight traditional apple cultivars of Southern Italy were analysed in terms of phenolic composition and free radical scavenging activity in comparison with commercial "Annurca" and "Gold Chief® Gold Pinkâ̂ - " cultivars. HPLC-UV-MS analysis of methanol extracts of the cultivars under examination showed significant differences in phenol distribution within the three main classes of hydroxycinnamates, dihydrochalcones, and flavan-3-ols. Such differences were found to be associated with the antioxidant activities as determined by the 2,2-diphenyl-1- picrylhydrazyl (DPPH) assay. A good correlation was observed between the percentage of reduced DPPH and the total phenol content (R = 0.79). Among all phenol classes, the flavan-3-ol content showed the highest correlation (R = 0.77). Almost all of the traditional cultivars examined exhibited a much higher phenol content (2- to 7-fold) and hydrogen donor activity (1.5- to 4-fold) than widely consumed cultivars like "Annurca" and "Gold Chief® Gold Pinkâ̂ - ". © 2012 Elsevier Ltd. All rights reserved.