Real-Time PCR assay was used to quantify the expression of marker genes of the salicylic acid, jasmonic acid and ethylene signaling pathways in seven
Solanum
lines after inoculation with a
Ralstonia ...solanacearum
phylotype I strain, R008. Four
Solanum lycopersicum
lines (CRA 66, Hawaii 7996, MST 32/1, Quatre carrées), one
S. tuberosum
line (Spunta), the wild
Lycopersicon cerasiforme
and
Solanum commersonii
were used for this investigation. Results revealed very little activation of the jasmonic acid pathway marker genes, lipoxygenase A (
LoxA
) and protease inhibitor II (
Pin2
), with no significant difference (
p
> 0.05) in fold change expression among the
Solanum
lines. In contrast the salicylic acid pathway marker genes, glucanase A (
GluA
) and
PR-1a
, and the ethylene pathway marker genes, osmotin-like (
Osm
) and
PR-1b
, were expressed at higher levels with a statistically significant difference (
p
< 0.05) in fold change expression among the
Solanum
lines. The resistant lines
L. cerasiforme
, CRA 66, Hawaii 7996 and
S. commersonii
showed stronger activation of the salicylic acid and ethylene marker genes than the moderately resistant cultivar (MST 32/1) and the susceptible lines (Quatre carrées and Spunta). The marker genes reached their highest expression levels earlier (4 h.p.i) in the resistant and moderately resistant lines than in the susceptible lines (48 h.p.i.). These results indicate that salicylic acid and ethylene signaling pathways have a significant role in defense against
R. solanacearum
. The timing and magnitude of the upregulation of gene expression may determine the plant ability to put up a defense response against the pathogen.
Shiga-toxigenic Escherichia coli (STEC) are important human pathogens associated with diarrhea and in some cases haemorrhagic colitis. Contaminated food derived from cattle and wildlife species are ...often associated with disease outbreaks. In this study, we report the prevalence, serogroup diversity and virulence profiles of STEC strains derived from cattle, rusa deer and pig. Of the 422 samples analyzed, STEC were detected in 40% (80/200) of cattle, 27.0% (33/122) of deer and 13.0% (13/100) of pigs. STEC isolates belonged to 38 O-serogroups whereby 5.2% (24/462) of the isolates belonged to clinically important EHEC-7 serogroups: O26 (n = 2), O103 (n = 1), O145 (n = 3) and O157 (n = 18). Fourteen serogroups (O26, O51, O84, O91, O100, O104, O110, O117, O145, O146, O156, O157, O177 and ONT) displayed multiple virulence profiles. We also identified two serovars (O117 and O119) in deer which are not well-documented in epidemiological surveys. 73.7% (28/38) of recovered O-serogroups are known to be associated with serious human illnesses including haemolytic uremic syndrome (HUS) and bloody diarrhea. STEC isolates harboring single genotypes stx1, stx2, eae and hlyA accounted for 3.0% (14/462), 9.1% (42/462), 47.6% (220/462) and 1.7% (8/462) of all STEC isolates screened, respectively. Virulence combinations stx1 and stx2 were harboured by 1.3% of isolates while strains with genetic profiles eae/hlyA were the second most prevalent amongst STEC isolates. The full known virulent genotypes (stx2/eae, stx1/stx2/eae, stx1/stx2/hlyA and stx2/eae/hlyA) were present in 22 of the 462 STEC strains. A total of 10 different virulence patterns were recovered amongst animal species. Phylogeny of the gnd gene showed that amongst STEC strains, serovar O100 outlined the main cluster. Fourteen (n = 14) different sequence types (STs) were identified from a panel of twenty (n = 20) STEC isolates. One of the isolate (PG007B) possessed a unique ST (adk 10, fumC 693, gyrB 4, icd 1, mdh 8, purA 8, recA 2) that could not be assigned using MLST databases. None of the ST's recovered in deer were observed in domestic species. Our findings shows that food associated animals found on the tropical island of Mauritius carry a diversity of STEC strains with many serovars known to be associated with human disease. This report indicates that increased awareness, surveillance and hygienic attention at critical stages of the human food chain are warranted.
•Cattle, rusa deer and pigs are colonized by STEC, with cattle as the principal reservoir.•Retail beef accounted for over 85% of the 74 STEC-positive food samples.•73.7% (28/38) of O-serogroups were previously linked to HUS or bloody diarrhea.•Two rarely documented serovars (O117 and O119) were recovered in rusa deer.•38.5% of STEC strains had multiple toxigenic profiles involving stx2 and/or - eae.
Eighteen
Salmonella isolates from both human and food (non-human) sources (fish, meat, and poultry) were characterized using conventional culture methods, biochemical, serological, and molecular ...analyses. REP-PCR and RAPD produced DNA profiles for differentiation purposes. Enterobacterial repetitive intergenic consensus (ERIC), repetitive extragenic palindronic (REP) and BOXAIR primers were selected for REP-PCR and two arbitrary primers, namely OPP-16 and OPS-11 were used for RAPD to generate DNA fingerprints from the
Salmonella isolates. REP-PCR method showed greater discriminatory power in differentiating closely related strains of the related strains of
Salmonella and produced more complex banding patterns as compared with RAPD. A dendogram was constructed with both sets of profiles using SPSS Version 13.0 computer software and showed that most human isolates were separately clustered from the non-human isolates. Two of the human isolates were closely related to some of the non-human isolates. A good correlation was also observed between the serogrouping of the O antigen and the molecular profiles obtained from REP-PCR and RAPD data of the
Salmonella isolates. The results of a principal coordinate analysis (PCA) corresponded to the clustering in the dendrogram.
Genetic variations among isolates of Banana streak virus (BSV) were assessed using two sets of primers. The virus, found in banana accessions in Mauritius, was compared to a Nigerian isolate from ...cultivar Obino l’Ewai (BSOEV). On the basis of the observed size of amplicons, some Mauritius strains were different from l’Ewai BSOEV. Both Southern blot hybridization and the nucleotide sequences of the PCR products confirmed that they were of episomal BSV origin. An isolate of sugarcane bacilliform virus (SCBV) was found to be also very similar to the BSV isolated from banana samples. Nucleotide sequence analysis showed that even the same size PCR products had differing sequences. The dendrogram placed the isolates from Mauritius in a cluster separate from BSV and SCBV from other geographical locations.
Background and Aims The phylogenetic relationships between species of Coffea and Psilanthus remain poorly understood, owing to low levels of sequence variation recovered in previous studies, coupled ...with relatively limited species sampling. In this study, the relationships between Coffea and Psilanthus species are assessed based on substantially increased molecular sequence data and greatly improved species sampling. Methods Phylogenetic relationships are assessed using parsimony, with sequence data from four plastid regions trnL–F intron, trnL–F intergenic spacer (IGS), rpl16 intron and accD–psa1 IGS, and the internal transcribed spacer (ITS) region of nuclear rDNA (ITS 1/5·8S/ITS 2). Supported lineages in Coffea are discussed within the context of geographical correspondence, biogeography, morphology and systematics. Key Results Several major lineages with geographical coherence, as identified in previous studies based on smaller data sets, are supported. Other lineages with either geographical or ecological correspondence are recognized for the first time. Coffea subgenus Baracoffea is shown to be monophyletic, but Coffea subgenus Coffea is paraphyletic. Sequence data do not substantiate the monophyly of either Coffea or Psilanthus. Low levels of sequence divergence do not allow detailed resolution of relationships within Coffea, most notably for species of Coffea subgenus Coffea occurring in Madagascar. The origin of C. arabica by recent hybridization between C. canephora and C. eugenioides is supported. Phylogenetic separation resulting from the presence of the Dahomey Gap is inferred based on sequence data from Coffea.
Mauritius is one of the largest world producers of
Anthurium cut flowers but outbreaks of bacterial blight have never been reported on the island. This work was about the characterisation and ...identification of bacterial strains isolated from
Anthurium andreanum,
Dieffenbachia maculata and
Aglaonema simplex in Mauritius. Fifteen strains, that showed the morphological properties of
Xanthomonas on conventional media, were tested on two semi-selective media (Esculin-trehalose and cellobiose-starch). ELISA tests using a panel of monoclonal antibodies were carried out and three out of 15 strains reacted with a
Xanthomonas-specific monoclonal antibody (MAb XII). Analysis using four sets of ribosomal primers revealed that the same three Mauritius strains shared conserved PCR products with reference xanthomonads including virulent strains of
Xanthomonas axonopodis pv.
dieffenbachiae (
Xad). BIOLOG tests and the Sherlock Microbial Identification system (MIDI) identified these three new strains at the species level as
X. axonopodis. The complementary tests that were carried out clearly confirmed that the three strains are xanthomonads and, moreover, a DNA probe which showed specificity to
Xad strains suggested that the three Mauritius strains are non-virulent forms of the pathogen causing
Anthurium blight.
The three Mycosphaerella species M. fijiensis , M. musicola and M. eumusae , that infect bananas, cause major problems to the exploitation of this crop around the world. Their differentiation is ...crucial to the understanding of their epidemiology and control. M. eumusae was only recognised as a species in 2000, before which the other two were known to occur on Musa . It is now very commonly present in several countries. Bananas being a major source of revenue for low-income countries, they remain an important export commodity for these developing countries. The genetic relatedness of these three species was investigated through sequence analysis of conserved genes, actin, tubulin and histone 3. All confirmed M. eumusae as being different from the other two. Previous data relied on ribosomal sequences. Primers developed by Johanson and Jeger (1993) and which are specific for M. musicola and M. fijiensis , were tested on all three species. M. eumusae had an amplification profile which allowed its differentiation from the other two. The amplified fragments from the three species were sequenced and sequence polymorphism was used for designing new primers. Two new sets of primers, EuY1/EuY5 and EuY2/EuY5, reported here produced profiles that consistently gave the same bands which were specific for the three species and can be used in conventional PCR for their differentiation.
Anthurium blight, caused by Xanthomonas axonopodis pv. dieffenbachiae, is a systemic disease of Anthurium and other aroids. The aims of this work were to study the genetic diversity among X. ...axonopodis pv. dieffenbachiae strains and to identify, from the polymerase chain reaction (PCR) profiles, DNA probes that would be specific for the pathovar dieffenbachiae. Twenty-five X. axonopodis pv. dieffenbachiae strains, isolated from different hosts and geographical locations including Mauritius, were fingerprinted using the random amplified polymorphic DNA (RAPD)-PCR technique. The fingerprints were analyzed by the National Taxonomy System Software (NTSYS). The specificity of some of the RAPD fragments selected from PCR profiles was tested by Southern analyses of the PCR products. Ten arbitrary primers were chosen from an initial set of 111 decamers. Two hundred and nine RAPD markers were generated in eight individual DNA profiles. A correlation was found between the serotypes and the RAPD profiles for some groups of isolates. A possible link was also observed between the host range of the isolates tested and their RAPD profiles for strains isolated from Dieffenbachia and Philodendron. These results were confirmed by Southern analysis. Cluster analysis by the unweighted pair group method, arithmetic average (UPGMA) confirmed that the pathovar is genetically diverse with some strains that were clustered together showing similar host preferences. DNA probes with a potential use in molecular diagnostics of Anthurium blight were identified. This preliminary work could be used to develop PCR primers that will enable the sensitive detection of the pathogen in latently infected plants.
Anthurium andraeanum is an important ornamental in the flower industry in Mauritius. Classical phenotype methods of identification, although still very useful, are difficult to use between very ...closely related Anthurium cultivars. The objectives of this study were to assess the genetic diversity of 12 A. andraeanum cultivars in Mauritius using random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers and identify cultivar specific markers for the genetic profiling of A. andraeanum cultivars. Polymorphism among the 12 cultivars was assessed using RAPD and ISSR primers. Reproducible results were used for statistical analysis. The presence and absence of bands were scored as 1 and 0, respectively to form a matrix from which a dendrogram was obtained using NTSYS. Dendrograms were obtained from matrices derived from RAPD and ISSR analyses to give an estimate of the genetic distance between the tested cultivars. Both ISSR and RAPD were found to be useful tools in differentiating locally grown A. andraeanum.
Aims: The genus Salmonella is a common agent of gastroenteritis in Mauritius, generating more cases of the disease during summer than during winter. The aims of this study were to assess the genetic ...diversity of isolates of Salmonella enterica by RAPD fingerprinting, and to establish the relationship between human and chicken isolates.
Methods: Twenty‐six isolates were obtained from hospital laboratories and commercial poultry producers locally.
Results: The RAPD profiles, biochemical and serological analyses showed that two of the chicken isolates were mistakenly identified as Salmonella. The genetic diversity of the remaining 24 isolates (five chicken and 19 human), confirmed as Salmonella, was analysed using four arbitrary primers, OPA‐10, OPR‐03, OPI‐06 and OPJ‐09, chosen from an initial set of 10 decamers. Seventy RAPD markers were generated in four individual DNA profiles.
Significance and Impact of the Study: Cluster analysis (UPGMA) performed using the NTSYS‐pc V 1.8 computer software, confirmed that some strains of Salmonella isolated from chicken were genetically similar to those isolated from humans. Furthermore, a 1 kbp band amplified using primer OPA‐10 was specific for the Salmonella genus as it was not amplified in any of the control bacteria.
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