Important results achieved at University of Tuscia, Viterbo, Italy
Psa mechanisms of infection and reactions of Actinidia’s plants
The research, developed by the Group and the Phytobacteriology and CIME (Interdepartmental Center of Electron Microscopy) of the University of Viterbo, in co-operation on Forest Ecology and Forest Management Group, Centre for Ecosystem Studies, University of Wageningen (Netherlands), will be published shortly in the prestigious American journal of plant pathology, Phytopathology, (apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-02-12-0019-R) entitled "Bacterial canker on kiwifruit in Italy: anatomical changes in the wood and in the primary infection sites" (Authors: M. Renzi, P. Copini, AR Taddei, A. Rossetti, L. Gallipoli, A. Mazzaglia, Balestra GM).
The study, which lasted about 3 years, after numerous assumptions, allows us to clarify important aspects of what are the strategies that are adopted by PSA to penetrate into plants of Actinidia spp. and, as the same plants react in time to attack this dangerous bacterium.
Optical Microscope: (f) Section leaf with spongy tissue (sp) and palisade (pp) from invaded cells (coloured) of PSA that alter entirely the typical organization of the leaf tissues. (g) Control section of leaf; epidermal cells (ec).
Through the study of plants of Actinidia spp. (A. chinensis and A. deliciosa) naturally infected by PSA and other artificially contaminated by different techniques, and also with the aid of specific microscopy techniques (optical, transmission, scanning) is revealed as the agent of bacterial canker is able to penetrate through natural openings (stomata, lenticels) or wounds and then spread through the xylem and the phloem vessels.
Particular to the optical microscope of plant tissue of A. chinensis showed many cells where PSA (colored purple) have completely invaded the phloem (f) and, after passing the cambium (c), have spread and have also colonized the xylem.
Through research has also been possible to highlight and correlate typical anatomical changes of the wood (reduction of the sections of conductive vessels, formation of tyloses, reduction of the growth rings) with the infection by this vascular pathogen. The same, internal alterations have also made it possible to show that, between the initial penetration of PSA into the plants and the evident manifestation of symptoms, an intervening space of time that, the application of specific dendrochronology, allow to study and to clarify all in detail.
Particular of a wood kiwifruit section by optical microscope analyzed to measure the density and the section of conductive vessels as a result of natural infections by PSA.
Moreover the research, that the practice of cut widely adopted throughout these years to re-growth of plants previously infected by PSA, showing little effect and in fact may encourage the survival of bacterial pathogens within plants with the subsequent infection of new tissues, and how its further spread can be facilitated through the infected sap.
(A) Sap containing PSA cells leakage from plant cut at crown level; (B) newly organs affected by PSA, developed from plant previously cut due to PSA infection; (C) Psa infection inside new leader of kiwifruit plant already cut after previous PSA infection.
The study thus allows to clarify important aspects of the biology and epidemiology of this bacterium plant pathogen, as to direct the development of appropriate strategies for containment/control of PSA, according to its own strategies of infection and reactions of Actinidia spp. plants to its attack.
Further info:
Dr. Giorgio M. Balestra - Senior Researcher
DAFNE (Department for Agriculture, Forestry, Nature and Energy) - University of Tuscia
Via S. Camillo de Lellis
01100 Viterbo - Italy
Phone: +39 (0)761 357474
Fax: +39 (0)761 357473
Mob.: +39 333 4246404
Email: balestra@unitus.it
Web: www.unitus.it
Skype: giorba5618
Personal Web: www.agraria.unitus.it/interna.asp?idCat=244