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This work was designed to study the efficacy of two types of silicon compounds (sodium silicate and potassium silicate) to control charcoal rot disease caused by Macrophomina phaseolina in vitro, u...

Bacterial spot disease caused by Xanthomonas axonopodis pv. vesicatoria is considered one of the major diseases of tomato crop worldwide. The objective of this paper was to study the effect of certain essential oils (EOs), lemongrass, oleum and thyme, on X. axonopodis pv. vesicatoria (PHYX14) for controlling bacterial spot disease in tomato plants. The tested three essential oils (EOs) showed antibacterial activity in vitro test at 1:10 concentration against the PHYX14.Thyme oil exhibited the highest inhibition against PHYX14 followed by lemongrass and finally oleum. Under greenhouse conditions, the effect of EOs on the bacterial spot of tomato was evaluated on tomato seedlings. Thyme oil exhibited the highest reducing of tomato bacterial spot followed oleum and then lemongrass. Results indicated that the application of the tested (EOs) to tomato plants two days after the infection caused the highest reduction of disease severity. While the application of oleum oil exhibited the highest induction of the oxidative enzymes, peroxidase (PO) and polyphenol enzyme (PPO). Also increased total phenolic contents of tomato leaves followed lemongrass and then thyme oil as compared by control. The application of EOs two days before the infection caused the highest induction of PO, PPO enzymes and total phenolic contents in tomato leaves than two days after the inoculation.

Salinity impedes soil and crop productivity in over 900 million ha of arable lands worldwide due to the excessive accumulation of salt (NaCl). To utilize saline soils in agriculture, halophytes (salt-tolerant plants) are commonly cultivated. However, most food crops are glycophytes (salt-sensitive). Thus, to enhance the productivity of saline soils, gypsum (CaSO4·2H2O) as well as bio-organic (combined use of organic materials, such as compost and straw with the inoculation of beneficial microbes) amendments have been continuously recognized to improve the biological, physical and chemical properties of saline soils. CaSO4·2H2O regulates the exchange of sodium (Na+) for calcium (Ca2+) on the clay surfaces, thereby increasing the Ca2+/Na+ ratio in the soil solution. Intracellularly, Ca2+ also promotes a higher K+/Na+ ratio. Simultaneously, gypsum furnishes crops with sulfur (S) for enhanced growth and yield through the increased production of phytohormones, amino acids, glutathione and osmoprotectants, which are vital elicitors in plants’ responses to salinity stress. Likewise, bio-organic amendments improve the organic matter and carbon content, nutrient cycling, porosity, water holding capacity, soil enzyme activities and biodiversity in saline soils. Overall, the integrated application of gypsum and bio-organic amendments in cultivating glycophytes and halophytes is a highly promising strategy in enhancing the productivity of saline soils.

Botrytis cinerea is one of the most destructive ascomycete pathogens affecting crops worldwide and causing severe yield losses. Broad-spectrum fungicides are used to control fungal pathogenic diseases, but pathogens develop resistance toward these fungicides through point mutations. In this study, we isolated and observed resistance mechanisms in B. cinerea. All five isolates considered in this study belonged to this pathogen species, which affects tomato fruits. The phenotypic resistance profile was analyzed in terms of specific resistance to multiple succinate dehydrogenase inhibitors (SDHI) and benzimidazole-based fungicides (boscalid, BosR, flypyram, FluR, carbendazim, CarMR), (BosRFluMRCarMR), (BosMRFluRCarR), (BosMRFluMRCarMR) (BosSFluSCarS). The Half maximal effective concentration (EC50) (µg/mL) value ranges were 1.10–3.51 forboscalid-resistant isolates, 1.05–2.25 for fluopyram-resistant isolates, and 0.89–3.82 for carbendazim-resistant isolates. To investigate the molecular mechanism of resistance, the Sdh-B and β-tubulin genes of the respective SDHI-resistant and carbendazim-resistant isolates were amplified, and their amino acid sequences were compared with those of sensitive strains. The SDHI-resistant isolate of B. cinerea showed mutations G282A and G372V, while the carbendazim-resistant one presented mutation E947A. Integrated disease management and the application of new fungicides with low resistance risk should be implemented in order to reduce the risk of resistance development in B. cinerea.

Background Green mold disease on citrus caused by Penicillium digitatum is the most serious and destructive disease. It is causing 90% of production losses during post-harvest handling. Results In this study, the activity of seven yeast isolates from lemons against P. digitatum, a fungal pathogen that causes the green mold disease in lemons, was isolated and examined. In vitro experiments showed that isolate three significantly reduced pathogen growths and were later identified as Schwanniomyces vanrijiae. In addition, 3% ethanolic extracts of propolis (EEP) caused a strong mycelial growth inhibition with inhibition halos of 1.4 cm. The use of S. vanrijiae treatments to protect lemon fruits from green mold has been reported (55%); however, reports describing the application of EEP are limited (40%). Thus, the effectiveness of the combination of S. vanrijiae and 3% EEP in an antagonistic mixture for protecting lemon fruits from P. digitatum was examined. EEP and S. vanrijiae treatments were applied alone and in combination in both in vitro and in vivo conditions. The combined application of 3% EEP + S. vanrijiae on lemon fruits significantly reduced the severity and incidence of green mold (80 and 93.7%, respectively) with much higher efficacy than either treatment alone. Lemon fruits treated with both S. vanrijiae and 3% EEP showed increased levels of antioxidants, peroxidase (POD), polyphenol oxidase (PPO), and phenol than the untreated control. Conclusion The results indicated that the combination of S. vanrijiae + 3% EEP can strongly protect lemon fruits from green mold compared with the sole application of either bioagent.

To obtain a clear understanding of the mode of action of potassium bicarbonate (PB), sodium silicate (SSi) and calcium chelate (CCh) solutions (1%) in inducing resistance to gray mold disease in table grapes, enzymatic and nonenzymatic investigations were carried out. In particular, changes in the activity of the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD), total phenolic content and total flavonoid content were studied. As indirect action, PB, SSi and CCh reduced the incidence of gray mold by 43%, 50% and 41%, respectively. The highest activity of SOD was detected at 48 h in SSi-treated tissue, PB-treated tissue and CCh-treated tissue, and it was 1.7-, 1.4- and 1.2-fold higher, respectively, compared to the control. The APX activity was significantly higher in SSi-treated tissue than in the control at 24, 48 and 72 h and showed an increase in activity 2-fold for all times. Additionally, PB, SSi and CCh increased the activity of POD by 1.4-, 1.2- and 2.7-fold at 48 h posttreatment, respectively. The results showed that CCh was the most pronounced salt to increase both total phenol and flavonoid contents by 1.3 and 2.1, respectively. Additionally, the three tested salts induced an increase in total phenols and total flavonoids at 48 h posttreatment. The obtained result is one more movement towards an overall understanding of the mechanism by which salt solutions act as antimicrobial agents against gray mold of table grapes.

The aim of this study is to assess the effect of extracts of Nerium oleander, Eucalyptus chamadulonsis and Citrullus colocynthis against bacterial spot disease of tomato and to investigate the induction of resistance by tomato (Solanum lycopersicum) in order to promote a sustainable management system. The antibacterial activity of aqueous and ethanol plant extracts was tested against Xanthomonas axonopodis pv. vesicatoria, isolate PHYXV3, in vitro and in vivo. The highest antibacterial activity in vitro was obtained with C. colocynthis, N. oleander and E. chamadulonsis, respectively. In vivo, ethanol extracts of N. oleander and E. chamadulonsis were more effective than aqueous extracts in reducing pathogen populations on tomato leaves. Under greenhouse conditions, application of the plant extracts at 15% (v/v) to tomato plants significantly reduced disease severity and increased the shoot weight of &lsquo, Super Marmande&rsquo, tomato. In most cases, plant extracts significantly increased total phenol and salicylic acid content of tomato plants compared to either healthy or infected ones. In addition, C. colocynthisand E. chamadulonsis extracts significantly increased peroxidase activity while only E. chamadulonsis increased polyphenol oxidase after infection with the causal agent. The results indicated that the plant extracts showed promising antibacterial activity and could be considered an effective tool in integrated management programs for a sustainable system of tomato bacterial spot control.

This study aimed to evaluate the efficiency of Enterobacter cloacae PS14 and Trichoderma asperellum T34 in the control of potato wilt, caused by Ralstonia solanacearum (Smith), under greenhouse and field conditions. In vitro, the endophyte E. cloacae PS14 caused the highest reduction of the pathogen growth among 7 screened bacteria. It produced an inhibition zone as 16.9 mm compared to a specific antibiotic (20.0 mm). E. cloacae PS14 was selected as an effective antagonistic bacterium to be compared to T. asperellum strain T34 for reduction of the disease as well as increasing the crop yield of potato plants. Both E. cloacae and T. asperellum reduced the disease severity up to 10.7–26.5%, respectively, under greenhouse and up to 26.6–36.6%, respectively, under field conditions. The results approved that both E. cloacae and T. asperellum increased the yield of the crop by 20.44–40.96%, respectively. Their mode of action was indicated by suppression of the pathogen as well as induction of plant systemic resistance. The induction of systemic resistance was confirmed by increasing the total phenol and salicylic acid contents as well as increasing the activities of peroxidase, lipoxygenase, and polyphenol oxidase in potato plants than the healthy or only infected plants. Production of siderophore, indole-3-acetic acid (0.577–0.884 μM), hydrogen cyanide (2.34–3.61 μg/ml), and salicylic acid (0.436–1.488 μg/ml) was confirmed by E. cloacae PS14 and T. asperellum T34, respectively, in vitro. The study recommends the new strain E. cloacae PS14, as new endophytic effective bacteria, in the control of R. solanacearum causing the potato wilt disease.

The efficiency of azadirachtin, jojoba oil, Reynoutria sachalinensis, azoxystrobin + difenoconazole, kresoxim methyl, propiconazole and sulphur in controlling powdery mildew disease of Grapevines c...

The study deal with potentiality of Saccharomycopsis fibuligera and essential oils for controlling the gray mold rot of guava fruits, caused by Botrytis cinerea . The endophytic yeast S. fibuligera was isolated from asymptomatic guava fruits and was tested for its ability to suppress gray mold along with eight essential oils. S. fibuligera successfully showed suppressive effect on mycelial growth B. cinerea comprising 48.52%, while thyme oil showed the highest inhibition impact of all tested essential oils, producing 26 mm inhibition zone at minimum inhibitory concentration value 0.2 µl/ml. 90.04% of total constituents of thyme oil was identified via GC–MS analysis. The major components were carvacrol, γ-terpinene, p-cymene and thymol. In vivo , thyme oil and S. fibuligera caused significant reduction in the disease at 78.6 and 67.9%, respectively. In conclusion, our study confirmed that thyme oil and S. fibuligera individually may be applied as future ecofriendly alternatives to synthetic fungicides for controlling the disease.

The aim of the present study was to evaluate the efficacy of some chemical compounds to management rust disease on common bean under greenhouse and field conditions. In vitro, the effect of four chemical compounds, i.e. phosphoric acid at concentrations 0.3 and 0.6%, benzoic acid, Bion® (BTH), and pyrocatechol at concentrations 4 and 8 mM from each, as well as fungicide, Tilt 25%, 0.25 and 0.5 cm3/l water on urediniospores germination of Uromyces appendiculatus was tested on water agar medium. All these compounds decreased the germination of urediniospores percentage. Under greenhouse and field experiments, application of these compounds led to decrease in disease incidence compared to the control treatments. Benzoic acid at 2015 growing seasons was the most effective in reduction of disease incidence more than the other compounds, whereas the disease incidence decreased from 59.92 to 21.43% and from 68.43 to 18.41% under greenhouse and field conditions, respectively.

Three different antagonistic bacterial isolates, Pseudomonas fluoresces (Pf2), Bacillus subtilis (Bs3) and Rahnella acquatilis (Ra39) restricted the growth of Pectobacterium atrosepticum , the causal agent of black leg disease of potato, in vitro . Under greenhouse and field conditions, potato plants pre-treated with the three antagonistic bacterial isolates, individually or in combination, showed reduced disease severity relative to non-treated control plants. All isolates produced siderophores in different degrees but did not produce indole acetic acid (IAA) or hydrogen cyanide (HCN).The obtained results indicated that combination of Pseudomonas fluoresces (Pf2), Bacillus subtilis (Bs3) and Rahnella acquatilis (Ra39) is beneficial in controlling black leg disease of potato caused by pectobacterium atrosepticum .

Streptomyces scabies (Thaxter) causes destructive and serious damages to many vegetable field crops, including potato. Fourteen pure isolates were obtained from naturally diseased potato tubers showing symptoms of common scab disease, collected from different localities of Sohag governorate, Egypt. All tested isolates were identified as S. scabies (Stc) according to morphological and biochemical tests. Isolate Stc 10 exhibited the highest activity of polyphenoloxidase enzyme, followed by isolate Stc 11, while isolate Stc 2 produced the lowest activity of this enzyme. Concerning the peroxidase activity, the isolates varied in their production; Stc 11 exhibited the highest activity enzyme, followed by isolate Stc 2, whereas isolate Stc 10 produced the lowest activity of enzyme. In regard with Tyrosine Amonnia Lyase (TAL) activity, isolate Stc 2 exhibited the highest activity, followed by isolate Stc 10, whereas isolate Stc 11 exhibited the lowest activity. Agarose gel electrophoresis of the PCR amplification products revealed a band representing the expected 279 bp DNA fragment in each DNA extracted from the highly pathogenic isolates Stc 10 and 11. The results demonstrated that PCR amplification of the nec1 gene could be used as a reliable marker for detecting pathogenic Streptomyces isolates on potato tubers.

Cellulosic date palm wastes may have beneficial biotechnological applications for eco-friendly utilization. This study reports the isolation of thermophilic cellulase-producing bacteria and their application in lactic acid production using date palm leaves. The promising isolate was identified as Paenibacillus alvei by 16S rRNA gene sequencing. Maximum cellulase production was acquired using alkaline treated date palm leaves (ATDPL) at 48 h and yielded 4.50 U.mL-1 FPase, 8.11 U.mL-1 CMCase, and 2.74 U.mL-1 β-glucosidase. The cellulase activity was optimal at pH 5.0 and 50°C with good stability at a wide temperature (40-70°C) and pH (4.0-7.0) range, demonstrating its suitability in simultaneous saccharification and fermentation. Lactic acid fermentation was optimized at 4 days, pH 5.0, 50°C, 6.0% cellulose of ATDPL, 30 FPU/ g cellulose, 1.0 g. L-1 Tween 80, and 5.0 g. L-l yeast extract using Lactobacillus delbrueckii. The conversion efficiency of lactic acid from the cellulose of ATDPL was 98.71%, and the lactic acid productivity was 0.719 g. L-1 h-1. Alkaline treatment exhibited a valuable effect on the production of cellulases and lactic acid by reducing the lignin content and cellulose crystallinity. The results of this study offer a credible procedure for using date palm leaves for microbial industrial applications.

In this study, we investigated the ability of DL-3-aminobutyric acid (BABA) to protect tomato against bacterial wilt caused by Ralstonia solanacearum. This was combined with studies of accumulation of total phenolic compounds, free and total salicylic acid (SA), and activity of enzymes related to plant defence, i.e., polyphenol oxidase (PPO) and catalase (CAT). Under greenhouse conditions, tomato plants pre-treated by soil drenching with BABA profoundly reduced disease severity of bacterial wilt compared to plants receiving a soil drench with water. Thus, BABA reduced leaf wilting index by 75.3 % and vascular browning index by 69.9 %, without any in vitro inhibitory activity on the pathogen. BABA treatment significantly reduced the population of R. solanacearum in stems of tomato plants and additionally also significantly increased both fresh and dry weight of roots and shoots of tomato plants compared with the inoculated control. Application of BABA resulted in a high increase in PPO activity both in plants with and without inoculation. Compared to water-treated plants, treatment with BABA also induced a significant increase of total phenolic compounds as well as of free and total SA in leaves of both inoculated and non-inoculated tomato plants at all sampling times. CAT activity decreased in tomato plants treated with BABA in comparison with the water-treated control plants and the decrease in activity correlated with an increasing total SA accumulation. These findings suggest that BABA treatment resulted in induction of resistance to bacterial wilt in tomato.

Ralstonia solanacearum (Rs) race 3 biovar 2, the cause of bacterial wilt, is an economically important pathogen in tropical, subtropical and temperate regions of the world. We investigated the induced defence responses against tomato bacterial wilt by the application of acibenzolar-S-methyl (ASM) and Pseudomonas fluorescens (Pf2) alone or in combination. Seedling treatments of tomato plants with either Pf2 or ASM significantly reduced disease severity of bacterial wilt (58 and 56% disease reduction, respectively) of tomato plants. The highest disease reduction (72%) resulted from a combined application of both Pf2 and ASM. The application of ASM alone increased seedlings biomass relative to infected control with 64.3%. Changes in the activities of polyphenol oxidase (PPO), s-glucosidase (s-GL) and peroxidase (PO) in tomato after the application of ASM and Pf2 and inoculation with Rs were studied. Significant changes (P ≤ 0.05) in the activities of PPO, s-GL and PO were found. These results indicate that the future integrated disease management programmes against tomato bacterial wilt may be enhanced by including foliar sprays and soil drench of ASM and P. fluorescens. This is the first report of the use of both ASM and Pf2 to control the tomato bacterial wilt disease under field conditions.

The efficiency of some commercial biological control agents (BCAs), Bio Zaid and Bio Arc, and resistance inducers chemicals (RICs) (salicylic acid and Bion) on management of cucumber powdery mildew, caused by Sphaerotheca fuliginea, was evaluated in vitro and in vivo. In vitro experiments revealed that application of the tested BCAs and RICs significantly reduced the disease severity, number of conidia per leaf area unit (cm) and reduced germination of conidiospores of the causal pathogen. Under field conditions, application of BCAs and RICs caused significant decrement in the disease severity with significant increment in the fruit yield compared with check treatments. On the average, application of Bion recorded the highest values, either in reducing the disease severity or in raising the average fruit yield followed by Bio Arc. On the other hand, applying salicylic acid (SA) recorded, on the average, the lowest efficiency in reducing disease severity and low values of fruit yield in both growing seasons.

The population dynamics of Xanthomonas campestris pv. vitians (Xcv) was studied both externally and internally in lettuce, tomato and pepper plants. In addition, the application of bactericides during transplant production period was carried out for the management of bacterial leaf spot of lettuce under greenhouse conditions. Epiphytic populations of Xcv were recovered on leaves of lettuce plants (105 CFU/g) 5 weeks after sprayed than the other plant species when inoculated with 108 CFU/ml of Xcv. When plants of each crop species infiltrated with the bacterium at 105 CFU/ml, the highest populations were developed in lettuce (108 CFU/cm2) followed by pepper with 106 CFU/cm2 and tomato with 105 CFU/cm2 10-days after infiltration. Application of a mixture of Maneb and Kocide or Kocide alone as a foliar spray on lettuce significantly reduced the incidence and disease severity of bacterial leaf spot by 29 and 27% respectively. Spread of the bacterium and development of the disease may partly be managed by avoiding intercropping of these plants commonly grown in close proximity to lettuce. For the management of leaf-associated populations of Xcv in lettuce, use of a mixture of Maneb and Kocide is advocated to minimize the effect of attacks.

Erwinia soft rot causes destructive and serious damage to many vegetable crops including potato in the field, transit and storage periods. The effect of certain cultural practices on the susceptibility of potato tubers to soft rot bacteria was studied and the results of this work can be summarised in the following: potato tubers harvested on 1 May first exhibited the highest disease incidence compared with those harvested on 15 May or 30 May. Harvesting on 15 June resulted in the lowest disease infection. The application of high levels of nitrogen fertiliser as urea (46.5%), ammonium nitrate (31%) and ammonium sulphate (20.5%) resulted in an increase of the susceptibility of potato tubers to bacterial soft rot disease. In contrast, the addition of phosphorous as superphosphate (15.5%) fertiliser caused the reverse effect. The addition of potassium as potassium sulphate (48%) alone at any of the tested levels showed no effect. The susceptibility of potato tubers to bacterial soft rotting disease was increa...

Erwinia soft rot causes destructive and serious damages to many vegetable crops including potato, in the field, transit and storage periods. The role of certain potato tuber constituents in the physiology of disease resistance has been investigated. Pectin substances and calcium contents of potato tuber had a pronounced role in the physiology of disease resistance. Alpha and Santa (less susceptible cultivars) contained the higher amount of pectin and calcium compared by Mirkal, Diamant, Askort, Geganite and Nicola cultivars (more susceptible cultivars). Tubers extracts of all healthy tested potato tubers cultivars contained fructose except Santa cultivar and glucose except Alpha and Mirkal cultivars. Tuber extracts of the more susceptible cultivars (Nicola and Askort) contained a higher concentration of glucose and fructose than those of less susceptible cultivars (Geganite, Mirkal, Santa, Alpha and Diamant).

This study investigated the induced defense responses and protective effects against Stemphylium vesicarium by application of Salicylic Acid (SA). The effect of SA to induce resistance in onion plants against Stemphylium vesicarium was investigated in greenhouse conditions. Different doses of SA (1, 2 and 5 mM) were tested in vitro; growth of S. vesicarium was not affected by SA treatment, foliage sprays of 2 mM SA significantly suppressed disease development up to 40.39% by day 15 after inoculation under greenhouse conditions. Changes in the activities of peroxidase, polyphenoloxidase, SA and phenolic content on onion after application of SA and inoculation with S. vesicarium were studied. Onion plants treated by SA and inoculated with the pathogen showed significantly higher peroxidase, poly phenoloxidase, SA content and phenolic content than inoculated water-treated plants.

The aim of this study was to evaluate mixtures of bioagents and resistance inducers for protection of cotton roots against root infecting fungal pathogens. Three biological control agents (BCAs); Trichoderma hamatum (TM), Trichoderma harzianum (TZ) and Paecilomyces lilacinus (PL) and two resistance inducers (RIs); Bion (benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester) (BTH), salicylic acid (SA) were applied individually or in combination to test their efficacy in controlling cotton root rot disease caused by Fusarium oxysporum (FO) and Pythium debaryanum (PD) under greenhouse and field conditions. In greenhouse experiments, all applied treatments protected cotton seedlings against FO root rot. Disease index percentage (DI%) was significantly reduced up to 78.8%, while germination percentage increased significantly up to 199.60% compared with the infected control. All treatments significantly reduced PD DI% compared to infected controls. In field experiments, the maximum protection of cotton roots against FO and PD resulted from application of TM + PL + SA + BTH, where DI% was reduced to 72.3% and 69.3% relative to infected controls, respectively. Increase in cell wall fractions (cellulose, hemicelluloses and lignin) resulted from application of both BCAs and RIs in case of PD. Lignin content significantly increased 1.68–1.93 (FO) and 1.07–1.39 (PD) fold over the infected controls. A significant increase in free phenolics content was positively proportional to the degree of plant resistance against the two pathogens. The main conclusion of this study is that by combining BCAs with RIs there was increased consistency of suppression of root rot of cotton seedlings caused by either F. oxysporum or P. debaryanum .

Xanthomonas axonopodis pv. vesicatoria was isolated from infected tomato seedlings grown in an open field in Egypt. All the tested isolates infected tomato plants but with different degrees of disease severity. In an attempt to manage this disease, tomato seeds and/or seedlings were treated with an antagonistic local isolate of Pseudomonas fluorescens as a suspension or its formulation or acibenzolar-S-methyl (BTH). When the above three treatments were applied to tomato seeds under laboratory conditions, they improved seed germination and seedlings vigour relative to control seeds treated with sterile distilled water and pathogen but P. fluorescens culture was the most effective. Under greenhouse and field conditions, combinations of the above treatments were used. All treatments significantly reduced disease severity of bacterial spot in tomato relative to the infected control. The biggest disease reduction compared to seedlings inoculated with the pathogen alone resulted from a foliar application of P. fluorescens. Combined application of P. fluorescens or its formulation with BTH reduced the pathogen population and increased seedling biomass and tomato yield relative to control seedlings.

This study aims to isolate and identify the causal pathogen of tomato bacterial wilt in Egypt. In 2008, tomato plants showing typical symptoms of bacterial wilt disease with no foliar yellowing were observed in Minia, Assiut and Sohag governorates, Egypt. When cut stems of symptomatic plants were submerged in water, whitish ooze was evident and longitudinal sections showed a brown discoloration in the vascular tissues. Bacteria were isolated on triphenyl tetrazolium chloride medium and fifteen isolates shown typical morphological and cultural characteristics were confirmed as Ralstonia solanacearum biovar 2 race 1. Pathogenicity tests showed that all isolates proved to be pathogenic to tomato plants, varied from 52 to 97% wilting. This is the first report of R. solanacearum biovar 2 race 1 causing bacterial wilt in tomato crop in Egypt.