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Papers by Hassan Ammouneh

ABSTRACT The life table of local strain of grape phylloxera on local grape varieties was examined... more ABSTRACT The life table of local strain of grape phylloxera on local grape varieties was examined and one resistant rootstock 41 B. Small root pieces from these varsities were taken directly from the field and used for the study. The results showed that there was a great variation in percentage survival, number of laid eggs, oviposition period, developmental time, number of nodosities and population between most tested local varieties and the rootstock. The results illustrated that "Kalb Tearr" and "Kasuofee" were more tolerant to local grape phylloxera than the other ones. In fact, the resistance of "Kalb Tearr" and "Kasuofee" was similar to that of 41 B rootstock. The results showed that "Baladi" and "Aswad Sharrar" were good and suitable hosts for such destructive insect.

Isolation and identification of a new Bacillus strain for amylase production

The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Am... more The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Amylolytic Bacillus sp were isolated on starch agar medium. The Bacillus SY134D was the best amylase producing isolate among two hundred and ten isolates showed the amylolytic activity. The closest phylogenetic neighbours according to 16S gene sequence, the Bacillus SY134D isolate was identified as Bacillus subtilis . The optimum temperature for amylase production was found to be 37°C. Amylase production occurred at pH 3.0-9.0 with a maximum at pH 5.0. The best enzyme activity was observed at pH 6.0 and temperature 70°C.

Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules called N-acy... more Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules called N-acyl-l-homoserine lactones (AHLs). These molecules are degraded by lactonases. In this study, six Bacillus simplex isolates were characterized and identified as a new quorum-quenching species of Bacillus. An aiiA gene encoding an AHL-lactonase was identified based on evidence that: (i) it showed high homology with other aiiA genes of Bacillus sp.; (ii) the deduced amino acid sequence contained two conserved regions, 104SHLHFDH111 and 165TPGHTPGH173, characteristic of the metallo-β-lactamase superfamily; and (iii) the protein had zinc-dependent AHL-degrading activity. Additionally, the expression of the aiiA gene was significantly up-regulated by 3-oxo-AHL. The AHL-lactonase inhibited multiplication of the 3-oxo-C6-AHL-producing plant pathogen Erwinia amylovora sy69 both in vitro and in planta. The results provide support for the use of the quorum-quenching functionality of B. simplex in the...

Bacillus thuringiensis was detected in 12.5% of soil samples collected from diff erent regions in... more Bacillus thuringiensis was detected in 12.5% of soil samples collected from diff erent regions in Syria and 25 B. thuringiensis isolates were found to be highly toxic to larvae of Ephestia kuehniella Zeller, Phthorimaea operculella Zeller, and Cydia pomonella L. (Lepidoptera), but not to the larvae of Culex quinquefasciatus (Diptera). Light microscopy investigation showed the presence of bipyramidal and cuboidal parasporal bodies produced by these isolates. Th e existence of diff erent cry genes in the tested isolates was studied using a PCR strategy with a set of general primers recognizing some of the cry genes reported in the relevant literature. Primers corresponding to 2 types of cry genes (cry1 and cry2) successfully amplifi ed DNA in all of the tested isolates. Moreover, the proteins encoded by these genes were detected in the SDS-PAGE of the purifi ed parasporal bodies. Th e 50% lethal concentration of the spore-crystal mixture of the 25 isolates against E. kuehniella larvae...

As a part of an ongoing nationwide programme focused on finding novel strains of Bacillus thuring... more As a part of an ongoing nationwide programme focused on finding novel strains of Bacillus thuringiensis (Bt) that are toxic to some of the major pests that impact economically important crops, we initiated a search for Bt isolates native to Syria. We succeeded in assembling a collection of 40 Bt isolates recovered from infected larvae of Galleria mellonella, Helicoverpa armigera and Ephestia kuehniella. Light microscopy showed that all isolates produce bipyramidal and cuboidal crystal proteins. The 50% lethal concentration of the spore-crystal mixture of the 40 isolates against E. kuehniella larvae varied from 3 to more than 200 µg g−1. A comparison of the LC50 values of the tested isolates with the reference strain Bt kurstaki HD-1 (20.55 µg g−1), showed that some of these isolates have a similar or up to six times higher toxicity potential. PCR screening revealed that all obtained isolates contain cry1 and cry2 genes, whereas only four contain cry9. Moreover, the proteins of 130 a...

As hydrolytic enzymes, xylanases catalyze the endohydrolysis of 1,4-beta-D-xylosidic linkages in ... more As hydrolytic enzymes, xylanases catalyze the endohydrolysis of 1,4-beta-D-xylosidic linkages in xylan, the major hemicellulose in hardwoods and non-wood fibers. Started from the middle of 1990s, the beneficial effect of xylanases in various industries was substantially reported (Javier Pastor et al., 2007). For instances, the addition of xylanases in the blended animal fat diet improved the body weight gains and feed absorption of the livestock due to better digestibility. On the other hand, the application of xylanases in baking assists the flour hemicellulose degradation and resulted in improving bread volume, crumb structure, and bread antistaling effect. Furthermore, xylanase was also being used for bio-conversion of lignocelluloses, especially xylan in wastes from agriculture or food industries into xylose and biofuel. The increasing environmental concern associates with the conventional chlorine-based pulp bleaching plans have driven the application of more eco-friendly bleac...

The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Am... more The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Amylolytic Bacillus sp were isolated on starch agar medium. The Bacillus SY134D was the best amylase producing isolate among two hundred and ten isolates showed the amylolytic activity. The closest phylogenetic neighbours according to 16S gene sequence, the Bacillus SY134D isolate was identified as Bacillus subtilis. The optimum temperature for amylase production was found to be 37°C. Amylase production occurred at pH 3.0-9.0 with a maximum at pH 5.0. The best enzyme activity was observed at pH 6.0 and temperature 70°C

JOURNAL OF PLANT PATHOLOGY

A total of 75 Erwinia amylovora isolates, collected primarily from fire blighted quince (Cydonia ... more A total of 75 Erwinia amylovora isolates, collected primarily from fire blighted quince (Cydonia oblonga) and pear (Pyrus syriaca and P. communis) shoots, were tested for copper resistance and streptomycin sensitivity. Sixty eight isolates, representing 90.6% of the total were inhibited by 10 μg/ml streptomycin and were thus regarded as streptomycin sensitive. On the contrary, three isolates that were not inhibited by 2000 μg/ml streptomycin were considered as resistant. Fifteen isolates grew well on casitone yeast extract medium in the presence of 1.2 mM copper sulfate and none survived on the same medium containing 2.4 mM copper sulfate, indicating that most of the Syrian E. amylovora isolates are copper tolerant and could cause severe problems even in copper heavily sprayed orchards.. The use of both bactericides in controlling fire blight disease in Syria is discussed.

JOURNAL OF PLANT PATHOLOGY

Thirty Erwinia amylovora strains, collected from the main rosaceous crop-growing regions of Syria... more Thirty Erwinia amylovora strains, collected from the main rosaceous crop-growing regions of Syria, were chosen as representatives of all major pathogenicity groups and were genetically studied by AFLP. Eight primer combinations were utilized and approximately 300 scorable bands in total were generated. Based on similarity coefficient, E. amylovora strains were placed into a main cluster containing two sub-clusters, indicating very low genetic variations among the studied pathogen. The existence of two plasmids, pEA29 (present in nearly all E. amylovora isolates) and pEL60 (present mainly in Lebanese strains), was confirmed using multiplex PCR in all tested Syrian E. amylovora strains, indicating that Lebanese and Syrian isolates may share a common origin.

Under natural conditions, plants are frequently subjected to biotic (i.e., pathogen infection, he... more Under natural conditions, plants are frequently subjected to biotic (i.e., pathogen infection, herbivores, etc..) and abiotic (i.e., low or high temperature, drought and salinity) constraints that cause considerable damage and limit plant productivity worldwide. A wide range of biotic and abiotic stresses results in the accumulation of Reactive Oxygen Species, ROS (H2O2, O2), Nitric Oxide ( NO) and cytosolic calcium ( Ca2+), indicating that plant responses to diseases and drought may operate, at least in part, through common molecular pathways. Additionally, stress-inducible genes have been categorised in two different groups: (a) genes that directly protect against environmental stresses and (b) genes that encode protein kinases. Intriguingly, protein kinases are also involved in disease resistance since many resistance genes (R genes) are in fact kinases. Here, we describe an interactor hunt using the bacterial virulent gene, VirPphA as a bait to screen an Arabidopsis thaliana cDN...

Advances in Horticultural Science

The life table of local strain of grape phylloxera on local grape varieties was examined and one ... more The life table of local strain of grape phylloxera on local grape varieties was examined and one resistant rootstock 41 B. Small root pieces from these varsities were taken directly from the field and used for the study. The results showed that there was a great variation in percentage survival, number of laid eggs, oviposition period, developmental time, number of nodosities and population between most tested local varieties and the rootstock. The results illustrated that "Kalb Tearr" and "Kasuofee" were more tolerant to local grape phylloxera than the other ones. In fact, the resistance of "Kalb Tearr" and "Kasuofee" was similar to that of 41 B rootstock. The results showed that "Baladi" and "Aswad Sharrar" were good and suitable hosts for such destructive insect.

Iranian journal of microbiology, 2014

Bacillus species are attractive industrial organisms due to their rapid growth rates leading to a... more Bacillus species are attractive industrial organisms due to their rapid growth rates leading to a short fermentation cycle and for their capacity to secrete important enzymes and proteins such as xylanase into the extracellular medium. Considering the industrial importance of xylanase, in this current study, Bacillus spp. were isolated from different soils and were screened for their xylanase production. Bacillus isolates used in this study were obtained from a national screening program carried out during 2006-2007 in which soil samples that covered areas throughout the interior of Syria were collected. The prepared inoculum from each of Bacillus isolates was aliquoted onto xylan agar plates, incubated at 30°C for 72 h and screened for xylanase synthesis. Xylanolytic isolates were selected depending on the clear zones of xylan hydrolysis. Fifteen isolates having the highest clearing zone were determined and grown in a solid state fermentation. Of the 15 isolates, three bacilli name...

The Plant Journal, 2006

The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of ef... more The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of effectors and AvrPto were examined in bean, tomato and Arabidopsis. Proteins were delivered by the RW60 strain of P. syringae pv. phaseolicola. RW60 causes a hypersensitive reaction (HR) in bean and tomato but is restricted without the HR in Arabidopsis. Dual avirulence and virulence functions in tomato and bean, respectively, were identified in virPphA homologues but only avrPtoB strongly enhanced virulence to Arabidopsis, overcoming basal defences operating against RW60. Virulence activity in both bean and Arabidopsis required regions of the C-terminus of the AvrPtoB protein, whereas elicitation of the rapid HR in tomato, with the matching Pto resistance gene, did not. The effect of AvrPtoB on Arabidopsis was accession-specific; most obvious in Wassilewskija (Ws-3), intermediate in Columbia and not detectable in Niedersenz (Nd-1) after inoculation with RW60 þ avrPtoB. Analysis of crosses between Ws-3 and Nd-1 indicated co-segregation for the AvrPtoB virulence function with the absence of the Nd-1 FLS2 gene which mediates recognition of bacterial flagellin. In planta expression of AvrPtoB did not prevent the HR activated by P. syringae pv. tomato DC3000 þ avrB, avrRpm1, avrRps4 or avrRpt2, but suppressed cell wall alterations, including callose deposition, characteristic of basal defence and was associated with reprogramming of the plant's transcriptional response. The success or failure of AvrPtoB in suppressing basal defences in Nd-1 depended on the timing of exposure of plant cells to the effector and the flagellin flg22 peptide.

Plant Pathology, 2013

ABSTRACT Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules cal... more ABSTRACT Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules called N-acyl-l-homoserine lactones (AHLs). These molecules are degraded by lactonases. In this study, six Bacillus simplex isolates were characterized and identified as a new quorum-quenching species of Bacillus. An aiiA gene encoding an AHL-lactonase was identified based on evidence that: (i) it showed high homology with other aiiA genes of Bacillus sp.; (ii) the deduced amino acid sequence contained two conserved regions, 104SHLHFDH111 and 165TPGHTPGH173, characteristic of the metallo-β-lactamase superfamily; and (iii) the protein had zinc-dependent AHL-degrading activity. Additionally, the expression of the aiiA gene was significantly up-regulated by 3-oxo-AHL. The AHL-lactonase inhibited multiplication of the 3-oxo-C6-AHL-producing plant pathogen Erwinia amylovora sy69 both in vitro and in planta. The results provide support for the use of the quorum-quenching functionality of B. simplex in the integrated control of the devastating fire blight pathogen.

Molecular Plant Pathology, 2002

virPphA is a major determinant of the pathogenicity of Pseudomonas savastanoi pv. phaseolicola to... more virPphA is a major determinant of the pathogenicity of Pseudomonas savastanoi pv. phaseolicola to Phaseolus bean. A family of homologues of virPphA was detected in pathovars of P. savastanoi and P. syringae. We examined the structure and activity of alleles designated virPphA, virPphA Pgy , and virPphA Psv from P. savastanoi pathovars phaseolicola, glycinea, and savastanoi, respectively, and avrPtoB from P. syringae pv. tomato. Sequencing showed that the virPphA Pgy homologue had a 48-bp central deletion in the open reading frame (ORF) compared with virPphA and virPphA Psv , but otherwise all three P. savastanoi alleles had > 98% identity at the DNA level. By contrast, AvrPtoB from P. syringae pv. tomato strain DC3000 was predicted to have only 51% amino acid similarity with VirPphA. All ORFs have an upstream hrp-box promoter indicating potential regulation by HrpL. Each cloned homologue was introduced into the P. savastanoi pv. phaseolicola strain RW60, which lacks a native plasmid carrying virPphA as part of a pathogenicity island (PAI), and which is not pathogenic on bean. The homologues all restored virulence, as measured by the development of water-soaked lesions in bean pods, and increased bacterial populations in leaves compared with RW60 alone. RW60 harbouring virPphA or virPphA Psv elicited a strong hypersensitive reaction (HR) in soybean cv. Osumi; the presence of avrPtoB caused a weak HR, but virPphA Pgy did not affect the null reaction observed in soybean with RW60 alone. A second effector gene, avrPphD, was detected on the genomic clones carrying virPphA Pgy and virPphA Psv . avrPphD was also present in both P. savastanoi pv. phaseolicola and P. syringae pv. tomato, but elsewhere in their genomes. Comparison of the genomic locations of virPphA and other effectors found in the P. savastanoi pv. phaseolicola PAI revealed the greatest divergence of the sequences surrounding virPphA to be in P. syringae pv. tomato.

Biocontrol Science and Technology, 2013

ABSTRACT As a part of an ongoing nationwide programme focused on finding novel strains of Bacillu... more ABSTRACT As a part of an ongoing nationwide programme focused on finding novel strains of Bacillus thuringiensis (Bt) that are toxic to some of the major pests that impact economically important crops, we initiated a search for Bt isolates native to Syria. We succeeded in assembling a collection of 40 Bt isolates recovered from infected 15 larvae of Galleria mellonella, Helicoverpa armigera and Ephestia kuehniella. Light microscopy showed that all isolates produce bipyramidal and cuboidal crystal proteins. The 50% lethal concentration of the spore-crystal mixture of the 40 isolates against E. kuehniella larvae varied from 3 to more than 200 mg g�1. A comparison of the LC50 values of the tested isolates with the reference strain Bt 20 kurstaki HD-1 (20.55 mg g�1), showed that some of these isolates have a similar or up to six times higher toxicity potential. PCR screening revealed that all obtained isolates contain cry1 and cry2 genes, whereas only four contain cry9. Moreover, the proteins of 130 and 65/70 Kda encoded by these genes were detected in the SDS-PAGE of the purified parasporal bodies. Flagellar serotyping classified 30 as 25 serovar kurstaki, six isolates serovar aizawai, one isolate cross-reacted with more than one H3 antisera and three were not typeable. Assays of toxicity of the aizawai isolates against third instar of G. mellonella showed that four, which contain cry9, have almost similar toxicity to the commercial strain Bt aizawai B401. Therefore, these isolates could be adopted for future applications to control 30 G. mellonella. Moreover, this study contributes to our knowledge of Bt diversity in Syria where to date very few collections have been described.

Australasian Plant Pathology, 2008

ABSTRACT A survey of all major pome fruit growing regions was conducted during 2005 and 2006 to e... more ABSTRACT A survey of all major pome fruit growing regions was conducted during 2005 and 2006 to establish whether Erwinia amylovora, the causal agent of fire blight, was present in Syria. Samples were collected from quince (Cydonia oblonga), pear (Pyrus communis) and apple (Malus domestica) trees suspected of being infected with E. amylovora. Seventy-five isolates of E. amylovora were recovered, mainly from quince and some from pear but none from apple. All isolates produced typical symptoms of fire blight when tested on immature pear fruit. Two isolates were shown to induce a delayed hypersensitivity reaction on tobacco. All the isolates were confirmed to be E. amylovora by PCR using primers specific for this bacterium. One set of primers amplifies a fragment of the native plasmid (pEA29) and a second set amplifies a fragment involved in the synthesis of amylovoran, the structurally unique exopolysaccharide of this bacterium. Fire blight was found to prevail in the Al-Zabadani region (Rif Damascus), an area with a moderate temperature range (10–29◦C) and high relative humidity (above 70%) during the blossom period. However, the diseasewas found to be restricted within Syria and observed only in isolated foci near the Lebanese border. This is the first isolation and identification of E. amylovora from Syria.

The Plant Journal, 2006

The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of ef... more The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of effectors and AvrPto were examined in bean, tomato and Arabidopsis. Proteins were delivered by the RW60 strain of P. syringae pv. phaseolicola. RW60 causes a hypersensitive reaction (HR) in bean and tomato but is restricted without the HR in Arabidopsis. Dual avirulence and virulence functions in tomato and bean, respectively, were identified in virPphA homologues but only avrPtoB strongly enhanced virulence to Arabidopsis, overcoming basal defences operating against RW60. Virulence activity in both bean and Arabidopsis required regions of the C-terminus of the AvrPtoB protein, whereas elicitation of the rapid HR in tomato, with the matching Pto resistance gene, did not. The effect of AvrPtoB on Arabidopsis was accession-specific; most obvious in Wassilewskija (Ws-3), intermediate in Columbia and not detectable in Niedersenz (Nd-1) after inoculation with RW60 þ avrPtoB. Analysis of crosses between Ws-3 and Nd-1 indicated co-segregation for the AvrPtoB virulence function with the absence of the Nd-1 FLS2 gene which mediates recognition of bacterial flagellin. In planta expression of AvrPtoB did not prevent the HR activated by P. syringae pv. tomato DC3000 þ avrB, avrRpm1, avrRps4 or avrRpt2, but suppressed cell wall alterations, including callose deposition, characteristic of basal defence and was associated with reprogramming of the plant's transcriptional response. The success or failure of AvrPtoB in suppressing basal defences in Nd-1 depended on the timing of exposure of plant cells to the effector and the flagellin flg22 peptide.

ABSTRACT The life table of local strain of grape phylloxera on local grape varieties was examined... more ABSTRACT The life table of local strain of grape phylloxera on local grape varieties was examined and one resistant rootstock 41 B. Small root pieces from these varsities were taken directly from the field and used for the study. The results showed that there was a great variation in percentage survival, number of laid eggs, oviposition period, developmental time, number of nodosities and population between most tested local varieties and the rootstock. The results illustrated that "Kalb Tearr" and "Kasuofee" were more tolerant to local grape phylloxera than the other ones. In fact, the resistance of "Kalb Tearr" and "Kasuofee" was similar to that of 41 B rootstock. The results showed that "Baladi" and "Aswad Sharrar" were good and suitable hosts for such destructive insect.

Isolation and identification of a new Bacillus strain for amylase production

The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Am... more The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Amylolytic Bacillus sp were isolated on starch agar medium. The Bacillus SY134D was the best amylase producing isolate among two hundred and ten isolates showed the amylolytic activity. The closest phylogenetic neighbours according to 16S gene sequence, the Bacillus SY134D isolate was identified as Bacillus subtilis . The optimum temperature for amylase production was found to be 37°C. Amylase production occurred at pH 3.0-9.0 with a maximum at pH 5.0. The best enzyme activity was observed at pH 6.0 and temperature 70°C.

Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules called N-acy... more Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules called N-acyl-l-homoserine lactones (AHLs). These molecules are degraded by lactonases. In this study, six Bacillus simplex isolates were characterized and identified as a new quorum-quenching species of Bacillus. An aiiA gene encoding an AHL-lactonase was identified based on evidence that: (i) it showed high homology with other aiiA genes of Bacillus sp.; (ii) the deduced amino acid sequence contained two conserved regions, 104SHLHFDH111 and 165TPGHTPGH173, characteristic of the metallo-β-lactamase superfamily; and (iii) the protein had zinc-dependent AHL-degrading activity. Additionally, the expression of the aiiA gene was significantly up-regulated by 3-oxo-AHL. The AHL-lactonase inhibited multiplication of the 3-oxo-C6-AHL-producing plant pathogen Erwinia amylovora sy69 both in vitro and in planta. The results provide support for the use of the quorum-quenching functionality of B. simplex in the...

Bacillus thuringiensis was detected in 12.5% of soil samples collected from diff erent regions in... more Bacillus thuringiensis was detected in 12.5% of soil samples collected from diff erent regions in Syria and 25 B. thuringiensis isolates were found to be highly toxic to larvae of Ephestia kuehniella Zeller, Phthorimaea operculella Zeller, and Cydia pomonella L. (Lepidoptera), but not to the larvae of Culex quinquefasciatus (Diptera). Light microscopy investigation showed the presence of bipyramidal and cuboidal parasporal bodies produced by these isolates. Th e existence of diff erent cry genes in the tested isolates was studied using a PCR strategy with a set of general primers recognizing some of the cry genes reported in the relevant literature. Primers corresponding to 2 types of cry genes (cry1 and cry2) successfully amplifi ed DNA in all of the tested isolates. Moreover, the proteins encoded by these genes were detected in the SDS-PAGE of the purifi ed parasporal bodies. Th e 50% lethal concentration of the spore-crystal mixture of the 25 isolates against E. kuehniella larvae...

As a part of an ongoing nationwide programme focused on finding novel strains of Bacillus thuring... more As a part of an ongoing nationwide programme focused on finding novel strains of Bacillus thuringiensis (Bt) that are toxic to some of the major pests that impact economically important crops, we initiated a search for Bt isolates native to Syria. We succeeded in assembling a collection of 40 Bt isolates recovered from infected larvae of Galleria mellonella, Helicoverpa armigera and Ephestia kuehniella. Light microscopy showed that all isolates produce bipyramidal and cuboidal crystal proteins. The 50% lethal concentration of the spore-crystal mixture of the 40 isolates against E. kuehniella larvae varied from 3 to more than 200 µg g−1. A comparison of the LC50 values of the tested isolates with the reference strain Bt kurstaki HD-1 (20.55 µg g−1), showed that some of these isolates have a similar or up to six times higher toxicity potential. PCR screening revealed that all obtained isolates contain cry1 and cry2 genes, whereas only four contain cry9. Moreover, the proteins of 130 a...

As hydrolytic enzymes, xylanases catalyze the endohydrolysis of 1,4-beta-D-xylosidic linkages in ... more As hydrolytic enzymes, xylanases catalyze the endohydrolysis of 1,4-beta-D-xylosidic linkages in xylan, the major hemicellulose in hardwoods and non-wood fibers. Started from the middle of 1990s, the beneficial effect of xylanases in various industries was substantially reported (Javier Pastor et al., 2007). For instances, the addition of xylanases in the blended animal fat diet improved the body weight gains and feed absorption of the livestock due to better digestibility. On the other hand, the application of xylanases in baking assists the flour hemicellulose degradation and resulted in improving bread volume, crumb structure, and bread antistaling effect. Furthermore, xylanase was also being used for bio-conversion of lignocelluloses, especially xylan in wastes from agriculture or food industries into xylose and biofuel. The increasing environmental concern associates with the conventional chlorine-based pulp bleaching plans have driven the application of more eco-friendly bleac...

The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Am... more The objective of the study was to isolate amylase producing bacteria from Syrian soil samples. Amylolytic Bacillus sp were isolated on starch agar medium. The Bacillus SY134D was the best amylase producing isolate among two hundred and ten isolates showed the amylolytic activity. The closest phylogenetic neighbours according to 16S gene sequence, the Bacillus SY134D isolate was identified as Bacillus subtilis. The optimum temperature for amylase production was found to be 37°C. Amylase production occurred at pH 3.0-9.0 with a maximum at pH 5.0. The best enzyme activity was observed at pH 6.0 and temperature 70°C

JOURNAL OF PLANT PATHOLOGY

A total of 75 Erwinia amylovora isolates, collected primarily from fire blighted quince (Cydonia ... more A total of 75 Erwinia amylovora isolates, collected primarily from fire blighted quince (Cydonia oblonga) and pear (Pyrus syriaca and P. communis) shoots, were tested for copper resistance and streptomycin sensitivity. Sixty eight isolates, representing 90.6% of the total were inhibited by 10 μg/ml streptomycin and were thus regarded as streptomycin sensitive. On the contrary, three isolates that were not inhibited by 2000 μg/ml streptomycin were considered as resistant. Fifteen isolates grew well on casitone yeast extract medium in the presence of 1.2 mM copper sulfate and none survived on the same medium containing 2.4 mM copper sulfate, indicating that most of the Syrian E. amylovora isolates are copper tolerant and could cause severe problems even in copper heavily sprayed orchards.. The use of both bactericides in controlling fire blight disease in Syria is discussed.

JOURNAL OF PLANT PATHOLOGY

Thirty Erwinia amylovora strains, collected from the main rosaceous crop-growing regions of Syria... more Thirty Erwinia amylovora strains, collected from the main rosaceous crop-growing regions of Syria, were chosen as representatives of all major pathogenicity groups and were genetically studied by AFLP. Eight primer combinations were utilized and approximately 300 scorable bands in total were generated. Based on similarity coefficient, E. amylovora strains were placed into a main cluster containing two sub-clusters, indicating very low genetic variations among the studied pathogen. The existence of two plasmids, pEA29 (present in nearly all E. amylovora isolates) and pEL60 (present mainly in Lebanese strains), was confirmed using multiplex PCR in all tested Syrian E. amylovora strains, indicating that Lebanese and Syrian isolates may share a common origin.

Under natural conditions, plants are frequently subjected to biotic (i.e., pathogen infection, he... more Under natural conditions, plants are frequently subjected to biotic (i.e., pathogen infection, herbivores, etc..) and abiotic (i.e., low or high temperature, drought and salinity) constraints that cause considerable damage and limit plant productivity worldwide. A wide range of biotic and abiotic stresses results in the accumulation of Reactive Oxygen Species, ROS (H2O2, O2), Nitric Oxide ( NO) and cytosolic calcium ( Ca2+), indicating that plant responses to diseases and drought may operate, at least in part, through common molecular pathways. Additionally, stress-inducible genes have been categorised in two different groups: (a) genes that directly protect against environmental stresses and (b) genes that encode protein kinases. Intriguingly, protein kinases are also involved in disease resistance since many resistance genes (R genes) are in fact kinases. Here, we describe an interactor hunt using the bacterial virulent gene, VirPphA as a bait to screen an Arabidopsis thaliana cDN...

Advances in Horticultural Science

The life table of local strain of grape phylloxera on local grape varieties was examined and one ... more The life table of local strain of grape phylloxera on local grape varieties was examined and one resistant rootstock 41 B. Small root pieces from these varsities were taken directly from the field and used for the study. The results showed that there was a great variation in percentage survival, number of laid eggs, oviposition period, developmental time, number of nodosities and population between most tested local varieties and the rootstock. The results illustrated that "Kalb Tearr" and "Kasuofee" were more tolerant to local grape phylloxera than the other ones. In fact, the resistance of "Kalb Tearr" and "Kasuofee" was similar to that of 41 B rootstock. The results showed that "Baladi" and "Aswad Sharrar" were good and suitable hosts for such destructive insect.

Iranian journal of microbiology, 2014

Bacillus species are attractive industrial organisms due to their rapid growth rates leading to a... more Bacillus species are attractive industrial organisms due to their rapid growth rates leading to a short fermentation cycle and for their capacity to secrete important enzymes and proteins such as xylanase into the extracellular medium. Considering the industrial importance of xylanase, in this current study, Bacillus spp. were isolated from different soils and were screened for their xylanase production. Bacillus isolates used in this study were obtained from a national screening program carried out during 2006-2007 in which soil samples that covered areas throughout the interior of Syria were collected. The prepared inoculum from each of Bacillus isolates was aliquoted onto xylan agar plates, incubated at 30°C for 72 h and screened for xylanase synthesis. Xylanolytic isolates were selected depending on the clear zones of xylan hydrolysis. Fifteen isolates having the highest clearing zone were determined and grown in a solid state fermentation. Of the 15 isolates, three bacilli name...

The Plant Journal, 2006

The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of ef... more The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of effectors and AvrPto were examined in bean, tomato and Arabidopsis. Proteins were delivered by the RW60 strain of P. syringae pv. phaseolicola. RW60 causes a hypersensitive reaction (HR) in bean and tomato but is restricted without the HR in Arabidopsis. Dual avirulence and virulence functions in tomato and bean, respectively, were identified in virPphA homologues but only avrPtoB strongly enhanced virulence to Arabidopsis, overcoming basal defences operating against RW60. Virulence activity in both bean and Arabidopsis required regions of the C-terminus of the AvrPtoB protein, whereas elicitation of the rapid HR in tomato, with the matching Pto resistance gene, did not. The effect of AvrPtoB on Arabidopsis was accession-specific; most obvious in Wassilewskija (Ws-3), intermediate in Columbia and not detectable in Niedersenz (Nd-1) after inoculation with RW60 þ avrPtoB. Analysis of crosses between Ws-3 and Nd-1 indicated co-segregation for the AvrPtoB virulence function with the absence of the Nd-1 FLS2 gene which mediates recognition of bacterial flagellin. In planta expression of AvrPtoB did not prevent the HR activated by P. syringae pv. tomato DC3000 þ avrB, avrRpm1, avrRps4 or avrRpt2, but suppressed cell wall alterations, including callose deposition, characteristic of basal defence and was associated with reprogramming of the plant's transcriptional response. The success or failure of AvrPtoB in suppressing basal defences in Nd-1 depended on the timing of exposure of plant cells to the effector and the flagellin flg22 peptide.

Plant Pathology, 2013

ABSTRACT Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules cal... more ABSTRACT Quorum sensing in Gram-negative bacteria is regulated by diffusible signal molecules called N-acyl-l-homoserine lactones (AHLs). These molecules are degraded by lactonases. In this study, six Bacillus simplex isolates were characterized and identified as a new quorum-quenching species of Bacillus. An aiiA gene encoding an AHL-lactonase was identified based on evidence that: (i) it showed high homology with other aiiA genes of Bacillus sp.; (ii) the deduced amino acid sequence contained two conserved regions, 104SHLHFDH111 and 165TPGHTPGH173, characteristic of the metallo-β-lactamase superfamily; and (iii) the protein had zinc-dependent AHL-degrading activity. Additionally, the expression of the aiiA gene was significantly up-regulated by 3-oxo-AHL. The AHL-lactonase inhibited multiplication of the 3-oxo-C6-AHL-producing plant pathogen Erwinia amylovora sy69 both in vitro and in planta. The results provide support for the use of the quorum-quenching functionality of B. simplex in the integrated control of the devastating fire blight pathogen.

Molecular Plant Pathology, 2002

virPphA is a major determinant of the pathogenicity of Pseudomonas savastanoi pv. phaseolicola to... more virPphA is a major determinant of the pathogenicity of Pseudomonas savastanoi pv. phaseolicola to Phaseolus bean. A family of homologues of virPphA was detected in pathovars of P. savastanoi and P. syringae. We examined the structure and activity of alleles designated virPphA, virPphA Pgy , and virPphA Psv from P. savastanoi pathovars phaseolicola, glycinea, and savastanoi, respectively, and avrPtoB from P. syringae pv. tomato. Sequencing showed that the virPphA Pgy homologue had a 48-bp central deletion in the open reading frame (ORF) compared with virPphA and virPphA Psv , but otherwise all three P. savastanoi alleles had > 98% identity at the DNA level. By contrast, AvrPtoB from P. syringae pv. tomato strain DC3000 was predicted to have only 51% amino acid similarity with VirPphA. All ORFs have an upstream hrp-box promoter indicating potential regulation by HrpL. Each cloned homologue was introduced into the P. savastanoi pv. phaseolicola strain RW60, which lacks a native plasmid carrying virPphA as part of a pathogenicity island (PAI), and which is not pathogenic on bean. The homologues all restored virulence, as measured by the development of water-soaked lesions in bean pods, and increased bacterial populations in leaves compared with RW60 alone. RW60 harbouring virPphA or virPphA Psv elicited a strong hypersensitive reaction (HR) in soybean cv. Osumi; the presence of avrPtoB caused a weak HR, but virPphA Pgy did not affect the null reaction observed in soybean with RW60 alone. A second effector gene, avrPphD, was detected on the genomic clones carrying virPphA Pgy and virPphA Psv . avrPphD was also present in both P. savastanoi pv. phaseolicola and P. syringae pv. tomato, but elsewhere in their genomes. Comparison of the genomic locations of virPphA and other effectors found in the P. savastanoi pv. phaseolicola PAI revealed the greatest divergence of the sequences surrounding virPphA to be in P. syringae pv. tomato.

Biocontrol Science and Technology, 2013

ABSTRACT As a part of an ongoing nationwide programme focused on finding novel strains of Bacillu... more ABSTRACT As a part of an ongoing nationwide programme focused on finding novel strains of Bacillus thuringiensis (Bt) that are toxic to some of the major pests that impact economically important crops, we initiated a search for Bt isolates native to Syria. We succeeded in assembling a collection of 40 Bt isolates recovered from infected 15 larvae of Galleria mellonella, Helicoverpa armigera and Ephestia kuehniella. Light microscopy showed that all isolates produce bipyramidal and cuboidal crystal proteins. The 50% lethal concentration of the spore-crystal mixture of the 40 isolates against E. kuehniella larvae varied from 3 to more than 200 mg g�1. A comparison of the LC50 values of the tested isolates with the reference strain Bt 20 kurstaki HD-1 (20.55 mg g�1), showed that some of these isolates have a similar or up to six times higher toxicity potential. PCR screening revealed that all obtained isolates contain cry1 and cry2 genes, whereas only four contain cry9. Moreover, the proteins of 130 and 65/70 Kda encoded by these genes were detected in the SDS-PAGE of the purified parasporal bodies. Flagellar serotyping classified 30 as 25 serovar kurstaki, six isolates serovar aizawai, one isolate cross-reacted with more than one H3 antisera and three were not typeable. Assays of toxicity of the aizawai isolates against third instar of G. mellonella showed that four, which contain cry9, have almost similar toxicity to the commercial strain Bt aizawai B401. Therefore, these isolates could be adopted for future applications to control 30 G. mellonella. Moreover, this study contributes to our knowledge of Bt diversity in Syria where to date very few collections have been described.

Australasian Plant Pathology, 2008

ABSTRACT A survey of all major pome fruit growing regions was conducted during 2005 and 2006 to e... more ABSTRACT A survey of all major pome fruit growing regions was conducted during 2005 and 2006 to establish whether Erwinia amylovora, the causal agent of fire blight, was present in Syria. Samples were collected from quince (Cydonia oblonga), pear (Pyrus communis) and apple (Malus domestica) trees suspected of being infected with E. amylovora. Seventy-five isolates of E. amylovora were recovered, mainly from quince and some from pear but none from apple. All isolates produced typical symptoms of fire blight when tested on immature pear fruit. Two isolates were shown to induce a delayed hypersensitivity reaction on tobacco. All the isolates were confirmed to be E. amylovora by PCR using primers specific for this bacterium. One set of primers amplifies a fragment of the native plasmid (pEA29) and a second set amplifies a fragment involved in the synthesis of amylovoran, the structurally unique exopolysaccharide of this bacterium. Fire blight was found to prevail in the Al-Zabadani region (Rif Damascus), an area with a moderate temperature range (10–29◦C) and high relative humidity (above 70%) during the blossom period. However, the diseasewas found to be restricted within Syria and observed only in isolated foci near the Lebanese border. This is the first isolation and identification of E. amylovora from Syria.

The Plant Journal, 2006

The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of ef... more The virulence and avirulence activities of members of the Pseudomonas syringae HopAB family of effectors and AvrPto were examined in bean, tomato and Arabidopsis. Proteins were delivered by the RW60 strain of P. syringae pv. phaseolicola. RW60 causes a hypersensitive reaction (HR) in bean and tomato but is restricted without the HR in Arabidopsis. Dual avirulence and virulence functions in tomato and bean, respectively, were identified in virPphA homologues but only avrPtoB strongly enhanced virulence to Arabidopsis, overcoming basal defences operating against RW60. Virulence activity in both bean and Arabidopsis required regions of the C-terminus of the AvrPtoB protein, whereas elicitation of the rapid HR in tomato, with the matching Pto resistance gene, did not. The effect of AvrPtoB on Arabidopsis was accession-specific; most obvious in Wassilewskija (Ws-3), intermediate in Columbia and not detectable in Niedersenz (Nd-1) after inoculation with RW60 þ avrPtoB. Analysis of crosses between Ws-3 and Nd-1 indicated co-segregation for the AvrPtoB virulence function with the absence of the Nd-1 FLS2 gene which mediates recognition of bacterial flagellin. In planta expression of AvrPtoB did not prevent the HR activated by P. syringae pv. tomato DC3000 þ avrB, avrRpm1, avrRps4 or avrRpt2, but suppressed cell wall alterations, including callose deposition, characteristic of basal defence and was associated with reprogramming of the plant's transcriptional response. The success or failure of AvrPtoB in suppressing basal defences in Nd-1 depended on the timing of exposure of plant cells to the effector and the flagellin flg22 peptide.