LIBRO-CONGRESO-CITRUS

leaves. Although XCT44 produces less exopolysaccharides than the reference strain XCT, this deficiency is
not involved in the phenotype observed in C. limon leaves. This study constitutes the first report on the
characterization of XC in the northwest of Argentina.
S12P25
The causal agent of Citrus Canker, Xanthomonas citri subsp. citri, enters in a reversible viable but
non culturable state induced by copper, that can be reverted by citrus leaf extract
Golmohammadi M. 1 , Llop P. 2 , Cubero J. 3 , and López M.M. 2
1 Iran Citrus Research Institute (ICRI), Dept. Plant Protection, Iran; 2 Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro
de Protección Vegetal y Biotecnología, Spain; and 3 Instituto Nacional de Investigación y Tecnología Agraria (INIA), Dpto. Protección
Vegetal, Spain. mlopez@ivia.es
Xanthomonas citri subsp. citri (Xcc) is a quarantine organism in the European Union, that causes Citrus Canker,
a severe bacterial disease that affects most commercial citrus species, but not present in the Mediterranean
countries. Copper compounds are widely used in the integrated management of this disease and have been
described as inducers of the viable but non culturable state (VBNC) in several plant pathogenic bacteria,
including Xcc. VBNC may be considered as a state previous to bacterial death or a survival strategy adopted
by bacteria in adverse conditions. To demonstrate the biological significance of VBNC in Xcc, experiments have
been performed in order to clarify two essential characteristics to consider this state as a survival strategy:
reversibility and durability. Entrance of Xcc into the VBNC state has been observed in low nutrient medium, or in
presence of copper at concentrations employed in field treatments and persistence of Xcc in VBNC condition has
been demonstrated until five months under copper exposure. Reversibility was demonstrated after addition of
culture media, or citrus leaf extract, both acting as chelating agents of copper ions. Culturability was evaluated by
colony counting and viability by membrane integrity, a respiratory test and a real-time RT-PCR system targeting
mRNA from gumD gene. This report demonstrates that this state is a reversible long term survival strategy that
may occur in the field after copper treatments, giving false negative results when checking for their efficiency.
S12P26
Effect of N-acetyl-L-cysteine (NAC) on the epiphytic fitness of Xanthomonas citri subsp. citri (Xcc)
in sweet orange
Picchi S.C., Inui-Kishi R.N., Takita M.A., Machado M.A., and de Souza A.A.
Centro APTA Citros Sylvio Moreira (IAC), Laboratório de Biotecnologia, Brazil. rosangela@centrodecitricultura.br
The leaf surface harbors bacterial epiphytes that are capable of influencing the cell-to-cell signaling system of
the plant pathogen Xcc, causal agent of Citrus Canker. Here, we have evaluated the role of bacterial attachment
and biofilm formation in leaf colonization during canker development on a susceptible variety of sweet orange.
NAC is a mucolytic agent that has anti-bacterial properties and also decreases biofilm formation by a variety
of bacteria, and copper-based products are routinely used as a standard control measure for Citrus Canker.
We investigated if it is possible to use NAC as an antimicrobial compound together with copper and the effect
of the NAC on the epiphytic fitness of bacteria. The Xcc GFP-labeled bacteria were inoculated by spraying on
the surface of sweet orange leaves. The bacterial cell multiplication and diffusion processes were observed
directly under fluorescence microscope at different intervals after inoculation. The results showed that NAC
had a detachment effect and that the leaves that sheets copper application, showed reduced lesions. CFU/mL
from leaves were counted, showing a reduction in Xcc concentration.
S12P27
Disruption of ParB alters the virulence of Xanthomonas citri subsp. citri
Ucci A.P.U., and Ferreira H.F.
1 Universidade Estadual Paulista (UNESP), Biological Sciences, Brazil. mandapiovesan@gmail.com
The Gram-negative bacterium Xanthomonas citri subsp. citri (Xcc) is the etiological agent of Citrus Canker, a
severe disease that affects all species and cultivars of citrus worldwide. Since there is not an effective control
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