BACTERIOPHAGE TRANSLOCATION IN TOMATO PLANTS AND
PROSPECTS FOR CONTROL OF TOMATO BACTERIAL WILT. A.
Obradovic (1), F. B. Iriarte (2), G. V. Minsavage (3), J. C. Hong (3), T. M. Momol (3), and
J. B. Jones (3)
(
), University of Belgrade, Faculty of Agriculture, Belgrade-
Zemun, Serbia; (2) Iowa State University, Plant Pathology Dept., Ames, IA;
(3) University of Florida, Plant Pathology Dept., Gainesville, FL, USA.
Abstract: Bacterial wilt caused by Ralstonia solanacearum is a serious soilborne
disease of many economically important Florida crops, such as tomato and
potato, and is caused predominantly by race 1, biovar 1. Since it is caused
by a soilborne pathogen with a wide host range, bacterial wilt is very difficult
to control once it becomes established in the field. Although considerable
effort has focused on identifying effective chemical treatments, extensive
research has focused on identifying biological control agents for use in plant
protection. Bacteriophages have been utilized for controlling plant pathogens
either in the rhizosphere or phyllosphere. In order to use phages for control
of this soilborne vascular tomato pathogen, it was necessary to determine
the ability of phages to survive in the rhizosphere and the possibility to be
absorbed by the plant root system and translocated to above-ground parts.
Therefore, we tested the systemic nature of bacteriophages by using tomato
plants and specific phage strain as a model system. In the first experiment
four-week old tomato plants with either damaged or undamaged roots were
drenched with phage suspension (approx. 10^8 PFU/ml). In three other
experiments only undamaged roots were used. Tissue samples were cut
from several locations on the plants and analyzed for phage concentration.
During a two-week period of observation, the phage strain was constantly
detected in the rhizosphere of drenched tomato plants, proving ability to
maintain its population without the presence of compatible host. Detection of
phages in roots and above-ground plant parts provided evidence for phage
uptake through the tomato root system and translocation within the plant
tissue. In order to study effectiveness of the host specific phage treatment for
control of tomato bacterial wilt in controlled conditions, three-week old tomato
plants were inoculated with bacterial wilt pathogen and drenched with a
suspension of lytic phages (approx. 10^8 PFU/ml) applied either three days
before, following inoculation, and/or three days after inoculation. The most
effective wilt control was achieved in treatments based on phage application
following inoculation. This indicates that phage application can contribute to
control of the disease even in conditions of artificial inoculation favoring
infection. Consequently, such treatment could potentially play an important
role in the integrated disease management strategy.