By Antonio Mazzucchi, Carla Lucchese, Umberto Mazzucchi
Patented phage therapy against pear and apple fire blight
Bacteriophages or phages are pathogenic viruses of bacteria. A virulent lytic phage attaches to the bacterial cell surface and then internally injects its nucleic acid. The infection allows the phage reproduction within the bacterial cell, which can be subjected to lysis and dies.
A phage virulent for E. amylovora, selected for high lytic capacity among 29 phages isolated in several places of Po Valley and Friuli-Venezia Giulia Italian regions, caused confluent lysis of 22 virulent E. amylovora strains isolated from different host plants at various locations in Northern Italy, including the provinces of Trento and Bolzano.
On right: Fire blight canker caused by Erwinia amylovora on pear shoot
To propagate the phage in the laboratory a strain of Pantoea vagans has been used, a common saprophyte enterobacterium closely related to E. amylovora, living in the phyllosphere of many plants, isolated from a pear tree which died from fire blight. The method involves application of the phage preparation both in the presence and absence of E. amylovora infections on host plants of interest; in the first case the activity of the phage will be to prevent or limit infections of E. amylovora (primary target); in the second case to infect other enterobacteria commonly living in the plant phyllosphere, in particular strains of P. vagans (secondary targets). In fact, a phage usually is able to infect species taxonomically related to that used in the primary isolation. Propagating on other enterobacteria, the phage proposed for therapy can multiply in the phyllosphere in the same niches inhabited by E. amylovora and therefore be available to infect occasionally immigrant pathogen cells. In the patented preparation kept in a common refrigerator at 4C°, the phage can survive at least one year. Phages are not harmful to humans and animals.
The property of the selected phage to infect secondary targets and to multiply in the natural environment avoids or reduces the need for repeated treatments. The phage becomes a factor of sustainable integrated pest management in order to contain E. amylovora populations and reduce disease pressure. This strategy solves the problem of short survival of phages exposed to abiotic environmental stresses (eg pH, t°C and especially ultraviolet radiation, particularly between 200-400 nm), the main obstacle to use phages in the fight against plant bacterial diseases in the field; for this reason it is recommended the phage preparations treatment just before sunset. During the growing season the dew wetting during the night favours the encounter of phage particles with bacterial cells. Phages associated with the bacteria can penetrate passively into the plant tissues at dawn, at the time of stomata opening.
Research authors say: "Our selected phage can be used in parks and gardens (eg cotoneaster), on hedges (eg hawthorn, Photinia), on borders (eg firethorn), in orchards (eg apple, pear, quince, medlar) or in the nursery of all host plants of E. amylovora, in an open or in a protected environment. The phage associated with the soil of the root ball or adherent to the neck or the roots of the plant to be transplanted can be so passively transferred in the new plantation as a potential, future antagonist of E. amylovora."
The phage preparation is the object of the Bologna University MO2013A000117 patent filed by the Italian Office Patent and Trademark-UIBM Italian Office.
Further info:
Knowledge Transfer Office
University of Bologna
Email: business.team@unibo.it
The authors:
Antonio Mazzucchi, Degree in Agricultural Sciences, Consulenze Fitopatologiche VPS Ltd., Castel San Pietro Terme (Bologna); Carla Lucchese, Technical Graduate of the Department of Agricultural Sciences of the University of Bologna; Umberto Mazzucchi, formerly Full Professor of Plant Pathology at the University of Bologna. The authors contributed equally to the work.