Buban t cost864 manuscript
Efficacy of Pantoea agglomerans strain HIP32 against Erwinia amylovora
, Tamás Lakatos1, Tímea Tóth1, László Dorgai 2, Ildikó Hudák3, Mária Hevesi4
1Research and Extension Centre for Fruit Growing, 4244 Újfehértó P.O.Box 38., Hungary
3Biotechn. Laboratory, Res. Centre of the Debrecen University, 4400 Nyíregyháza, Hungary
4Corvinus University, Faculty of Horticult. Sci., Dept. of Pomology, 1118 Budapest, Hungary *
corresponding author: [email protected] Abstract.
When a high level of P. agglomerans
HIP32 population is present in the blossoms
- steadily established after the first-, or rebuilt by the second treatment - a sizable native Erwinia amylovora
population is measurable only within a few hours after the treatment. The
consequent decrease in the antagonist population results in the continuous presence of the
pathogen at relatively high level. Results of inoculation experiments under control ed
conditions prove that P. agglomerans
HIP32 treatment results in a significant reduction in the E. amylovora
population size, associated with convincing decrease in the index of infection.
Biological control of fire blight, the bacterial disease caused by E. amylovora
can be achieved by applying bacterial antagonists onto the flowers before a sizable epiphytic
population of the pathogen is established , . The Pantoea agglomerans
(HIP32) isolated from apple cv. Starking Delicious leaves in Hungary  is a potential
Material and Methods.
Idared (in 2005) as wel as Jonica, Pinova, Idared and Royal Gala
(in 2006) apple trees on M.9 rootstock were sprayed with HIP32 twice during bloom time in
the years of 2005 and 2006 (109 and 108 cfu/ml in 10 mM PBS, respectively). Check trees
were sprayed with PBS. Estimation of the bacterial population size in the flowers was done
by dilution plating on King B medium (HIP32) and Mil er-Schrott medium (native E. amylovora
) in 2005, but on Luria-Bertani medium (HIP32) and Chromocult coliform agar (E. amylovora
) in 2006. Incidence of blossom blight and shoot blight in the field was monitored in
Inoculation experiments were carried out under control ed conditions. Flowers from trees
treated with HIP32 in the field (2005), or treated with HIP32 ChlR in the laboratory (108 cfu/ml,
2006) were inoculated by E. amylovora
strain Ea1 KanR, (106 cfu/ml in 2005 and 105 cfu/ml in
2006). Bacterial population sizes were measured by dilution plating on mediums amended
with chloramphenicol and kanamycin, respectively. The index of infection was calculated by
an equation  considering both the occurrence and severity of blossom blight scored by the
– partly modified – rating scale of Pusey .
Analysis of variance was done with SPSS program package, mean separation by Tukey’s.
While comparing population sizes, the ln
transformed data were used.
Results and Discussion.
A rainfal of 7.4 mm a day after the first spraying in 2005 caused a
decrease in the ratio of flowers with sizable antagonist population merely to 20%. The 2nd
and 4th day fol owing the second spraying, however, the population size of HIP32 remained
at a steady level of about 106 cfu/flower. Population size of E. amylovora
on the 4th day after
the second treatment was 3-4x103 cfu/flower in two of the 15 samples from the check trees
and was not detectable in flowers of treated ones. Probably the pathogen could not be
establish due to the cold weather. The pathogen population in the flowers of trees treated in
the field and inoculated in the laboratory with E. amylovora
Ea1 KanR was significantly
(p<0.01) less than in the check flowers (3.75x104 vs. 1.00x106 cfu/flower).
The results of field trials in 2006 (Tab. 1) indicate that a stably established, high HIP32
population (see cv. Royal Gala), or a population rebuilt by the second treatment (Jonica)
coincides with a native population of E. amylovora
measurable at the beginning of the
experiment only (Jonica), after that it is reduced to, or stays at a very low, though detectable
level (Royal Gala, Jonica). A steadily decreasing antagonist population is paral eled with the
continuous presence of the pathogen at a measurable level (Pinova). As a function of HIP32
ChlR treatment, the significant reduction in the E. amylovora
population size is associated
with a convincing decrease in the index of infection (Tab. 2). Due to the low temperature in
both years, the incidence of blossom blight in the field was not high enough to estimate the
Population sizes of Pantoea agglomerans
HIP32 and native Erwinia amylovora
2 hours 2nd day/A1
2 hours 2nd day/A1
1.3x103 1.3x102 2.0x103
– 5.8x102 3
2.0x101 1.4x103 3
Royal Gala P.a.
2nd day after the 1st spraying, just before the 2nd treatment 2
2nd day after the 2nd spraying 3
number of replications from 6 ones with detectable level (<1x101 cfu/blossom) of pathogen
Data with various letters differ significantly at p<0.05 with the cv. Royal Gala and at p<0.001
Bacterial populations and disease rating in artificially infected blossoms of apple cultivars
Population sizes (cfu/blossom)1
Jonica P. agglomerans
strain HIP32 ChlR 8.45x105
Pinova P. agglomerans
strain HIP32 ChlR 2.9 x106
the 4th day after inoculation 2
the 5th day after inoculation
Data with various letters within a cultivar differ significantly at p<0.05
 Johnson K.B. et al
. (1993) Phytopathology
83: 995-1002. Book
 Stockwel W.O. (2002) In
Lindow S.E. et al.
(Eds) Phyl osphere Microbiology, APS Press,
 Bertrand P.F., Gottwald T.R. (1978) In
Zehr E.I. (Ed.) Methods for evaluating plant fungi-
cides, nematicides and bactericides, APS Press, St. Paul, pp. 179-181. Proceedings
 Hevesi M., El-Arabi K.F. (1999) Acta Horticulturae 489: 619-622.
 Pusey P.L. (1999) Acta Horticulturae 489: 521-524.
This project of BAROSS-2-2005-0013 is supported by
the National Office for Research and Technology;
FACULTY OF HISTORY Problems in the History of Science and Technology Michaelmas Term 2005 The following seminars will be held on Wednesday at 5 p.m. (except in Week 6, when the seminar will begin at 4pm) in the History of Science and Technology Seminar Room, Modern History Faculty. They will be preceded by tea in the Faculty Common Room at 4.40 p.m. (except in Week 6, when the se
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