LIBRO-CONGRESO-CITRUS

S12
S12P32
Bacteriostatic and bactericidal activity of different essential oils to alternative control in vitro of
Xanthomonas citri subsp. citri
Sauer A.V. 1 , Santos E.M. 1 , Zuliani-Gonçalves A.M.O. 1 , Nocchi P.T.R. 1 , Nunes W.M.C. 1 , and Bonato C.M. 2
1 Universidade Estadual de Maringá (UEM), Núcleo de Pesquisa em Biotecnologia Aplicada (NBA), Centro de Ciências Agrárias (CCA),
Brazil; and 2 Universidade Estadual de Maringá (UEM), Centro de Ciências Agrárias (CCA), Brazil. alinevanessasauer@hotmail.com
Xanthomonas citri subsp. citri is the causal agent of Citrus Canker, which is easily disseminated and
there has been no effective control until now. Excessive use of pesticides causes problems of human and
environmental contamination, and the selection of resistant pathogens. Thus, the study of alternative
control methods with a bactericidal action is critical to mitigate the adverse effects mentioned above.
The evaluation of the chemical components of essential oils indicated that some of these may change
their activity and have bactericidal action. The aim of this study was to evaluate the Minimum Inhibitory
Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of essential oils of Citrus aurantium,
Cymbopogon winterianus, Foeniculum vulgare, Pinus elliottii and Ocimum gratissimum. The method of
micro dilution plate was used to evaluate the MIC. Subsequently, an aliquot of 5μl (from the incubation
used for determination of MIC) was used to analyze the MBC, using Petri plates containing Nutrient Agar
(NA), as a growing medium. The results showed bactericidal activity of the essential oils, however C.
winterianus had the lowest concentration among the oils tested (MIC = 0.007 µl/ml and MBC = 0.487 µl/
ml). With the result of the MIC (0.007 µl/ml) C. winterianus is considered bacteriostatic, and only from
0.487 µl/ml it would be bactericidal.
S12P33
Canker control by the siderophore pyochelin from Pseudomonas fluorescens
Adler C. 1 , Lami M.J. 1 , de Cristobal R.E. 1 , Filippone M.P. 2 , Castagnaro A.P. 2 , and Vincent P.A. 1
1 Instituto Superior de Investigaciones Biológicas (INSIBIO), Argentina; and 2 Estación Experimental Agroindustrial Obispo Colombres
(EEAOC), Biotecnología, Argentina. conadler@uolsinectis.com.ar
This work shows the identification of a compound able to inhibit Xanthomonas citri pv. citri growth in vitro and
in vivo. Firstly, we isolated from environmental samples, bacteria able to inhibit X. citri pv. citri (Citrus Canker
agent) in vitro. Among the selected isolates, we focused in one showing a remarkable activity. The strain
was characterized as Pseudomonas fluorescens after sequencing its 16S rDNA and analyzing the sequence
with BLASTn. Purification and chemical analysis of the active compound allowed us to assign the inhibitory
activity to pyochelin (Pch). Since this molecule is a siderophore, we wondered if the inhibition observed was
a result of iron scavenging. Surprisingly, when we supplemented media with an excess of iron, we observed
practically no change in the inhibition activity. In an attempt to identify the action mechanism of pyochelin,
we evaluated the ability of pyochelin to generate reactive oxygen species (ROS) within a culture of X. citri pv.
citri and its correlation with the inhibitory activity. In fact, we observed increased ROS levels when Pch was
added. In addition, the reducer agent ascorbic acid, lowered ROS levels and the antibiotic activity implying
that inhibition is probably caused by oxidative stress. Finally, we studied the use of Pch in a model of canker
disease. Pch showed to reduce canker formation on leaves of ‘Eureka’ and ‘Lisbon’ variety plants. These
results show Pch as a promising compound for Citrus Canker biocontrol.
S12P34
Genetic response of sweet orange treated with chitosan to the infection of Xylella fastidiosa
Coqueiro D.S.O. 1 , Rodrigues C.M. 2 , Souza A.A. 2 , Takita M.A. 2 , Kishi L.T. 2 , and Machado M.A. 2
1 Universidade Federal da Bahia (UFBA), Biochemistry, Brazil; and 2 Centro de Citricultura Sylvio Moreira, Instituto Agronômico (IAC),
Laboratory of Biotechnology, Brazil. marcos@centrodecitricultura.br
One alternative that has been widely studied of disease control is the use of chitosan. This study aimed
to generate and evaluate the transcriptome of sweet orange (Citrus sinensis) plants treated with chitosan,
challenged or not with Xylella fastidiosa (Xf). Seven months old sweet orange plants grafted on ‘Rangpur’
212 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012