Kamal A.M. Abo-Elyousr

Antibacterial activity of certain plant extracts against bacterial wilt of tomato

Abstract Five isolates of Ralstonia solanacearum were isolated from a naturally wilted root of tomato plants grown in Assiut governorate. The antibacterial activity of extract of Datura, Garlic and Nerium were tested in controlling R. solanacearum in vitro and in vivo. Garlic exhibited the strongest antibacterial activity against bacterial wilt in vitro and in vivo followed by Datura and then Nerium. Cold water extracts of these plant species were more effective than hot water extract in the development of the disease in vivo. In greenhouse experiments, the application of the tested plant extract to soil at the time of inoculation, two days before inoculation and two days after inoculation the pathogen, significantly reduced the disease index of wilt on Super Marmande tomato cultivars. The application of plant extracts at the same time as inoculation resulted in the highest reduction of disease index.

Note Biological Control of Fusarium Wilt in Tomato by Plant Growth-Promoting Yeasts and Rhizobacteria

Three plant growth-promoting yeasts and two rhizobacteria were tested for controlling tomato wilt caused by Fusarium oxysporum f. sp. lycopersici under greenhouse and field conditions. Under greenhouse and field conditions, all treatments were significantly reduced disease severity of tomato wilt relative to the infected control. The highest disease reductions in pots (75.0, 67.4%) and field (52.5, 42.4%) were achieved by Azospirillum brasilense and Bacillus subtilis compared to infected control. Under field condition all treatments produced the highest tomato yield compared to the control plants inoculated with the pathogen.

Management of Tomato Root-knot Nematode Meloidogyne incognita by Plant Extracts and Essential Oils

The effect of plant extracts of eucalyptus (Eucalyptus chamadulonsis), garlic (Allium sativium), marigold (Tagetes erecta) and neem (Azadirachta indica) and essential oils were tested on the suppression of root-knot nematode Meloidogyne incognita under greenhouse and field conditions. In vitro study, all tested treatments had nematicidal effect on nematode juveniles after 24 and 48 hours from exposures. The highest percentage of nematode mortality was achieved by application of neem extract (65.4%), essential oils (64.4%) and marigold extract (60.5%), followed by garlic and eucalyptus extracts (38.7-39.5%). Under greenhouse and field conditions, neem extract and essential oils treatments were more effective in reducing population numbers of the M. incognita in soil and root gall index compared to other treatments. In field experiments, the maximum protection of tomato plant against root-knot nematode was obtained by application of neem and essential oil treatments, 44.2 and 32.6%, respectively.

Effectiveness of plant extracts to control purple blotch and Stemphylium blight diseases of onion (Allium cepa L.) in Assiut, Egypt

The present investigation aimed to isolate the causative agents of onion purple blotch and Stemphylium blight diseases and evaluate the efficacy of certain plant extracts against the two identified pathogens, in vitro and under greenhouse condition. Fourteen isolates of S. vesicarium and two isolates of Alternaria porri were tested for pathogenicity. The results indicated that all isolates were able to produce the symptoms of Stemphylium blight and onion purple blotch diseases with different degrees of severity ranging from 10.42 to 81.25%. A. porri No. 6022 caused the highest disease severity (81.25%), while S. vesicarium No. 6003 was the best one out of the tested 14 isolates (37.5%). Antifungal activity of some aqueous plant extracts (Azadirachta indica, Cydonia oblonga, Datura stramonium, Eucalyptus globulus, Foeniculum vulgare, Ocimum basilicum, Rosmarinus officinalis and Salix mucronata) was assayed in vitro by dry weight technique. The data indicated that there were significant differences between these extracts in their effect on fungal growth of A. porri and S. vesicarium and the best were A. indica and D. stramonium. Under greenhouse conditions, application of the aqueous extract of A. indica either before or after 48 h A. porri inoculation produced the highest reduction in disease severity comprising 70 and 74.7%, respectively. On the other hand, the highest percentage of disease reduction before and after 48 h S. vesicarium inoculation was produced by Ridomil gold plus reached to 84.4 and 95.8% respectively, followed by the aqueous extract of A. indica (74.1 and 89.7, respectively). According to our results, it can be concluded that plant extracts of A. indica and D. stramonium can be used for the biocontrol of purple blotch and Stemphylium blight diseases instead of fungicides to minimise the risks and hazards of using toxic fungicides.

Salicylic acid induced systemic resistance on onion plants against Stemphylium vesicarium.

Abstract 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.

Impact of compost application on Fusarium wilt disease incidence and microelements contents of basil plants

Fusarium oxysporum was isolated from stem of basil plants showing symptoms of wilt, stem blight and collar root rot. Pathogenicity tests indicated that F. oxysporum f. sp. basilici is the causal agent of this disease. This is the first report of this pathogen in Egypt. The suppressive effects of six types of composts on Fusarium wilt disease incidence in basil were evaluated under greenhouse conditions. The effectiveness of these composts and their relation to the microelements content in treated plants was also assessed. Soil treatments with Khaya and Eucalyptus composts significantly reduced the infection percentage and disease severity of basil wilt. Otherwise, the applications of Araucaria, Datura, Ficus and Azadirachta composts showed no effect on both infection percentage and disease severity. Moreover, the Khaya and Eucalyptus compost treatments increased the levels of Iron (Fe), Zinc (Zn) and Manganese (Mn) in treated basil plants than application of Araucaria, Datura, Ficus and Azadirachta composts. In the case of Copper (Cu) content, it was significantly higher only in Eucalyptus-compost-treated plants than in other compost applications. These composts not only reduced the disease incidence but also increased both fresh and dry weight (FW and DW) and microelements contented in basil treated plants. In general, although soil amendment with either Khaya or Eucalyptus compost can reduce the disease incidence of Fusarium wilt on basil plants, microelements contented; FW and DW of these effects can be variable depending on their levels added in soil. According to the results of this study, it can be concluded that the use of compost in the soil as an organic fertiliser increased exchangeable form of microelements in the soil and also the availability of these elements by basil plants.

Talaromyces pinophilus strain AUN-1 as a novel mycoparasite of Botrytis cinerea, the pathogen of onion scape and umbel blights

This study aimed to investigate the mycoparasitism of Botrytis cinerea, the pathogen of scape and umbel blights of onion seed crops, by endophytic Talaromyces pinophilus. The dual culture test showed that the antagonistic potentiality of T. pinophilus against B. cinerea depend on the mycoparasitism that was morphologically detected by the formation of mycelial overgrowth. Moreover, the light micrograph of the mycelia at the contact zone exhibited that the hyphae of T. pinophilus penetrated and grew intracellularly inside the hyphae of B. cinerea. A more illustrative figure of the establishment of coiled hyphae as well as the conformation of the penetration process was assayed by SEM and TEM analyses. SEM micrograph revealed that the hyphae of T. pinophilus grew along hyphae of B. cinerea, attached, coiled around the host hypha and generated pseudoappressorium. A clear disintegration of cell wall of the host hypha was observed at the penetration site. The micrographs of TEM exhibited the ability of T. pinophilus to produce pseudoappressorium, penetrate and then entere a hypha of B. cinerea causing distinct cytoplasmic disorganization. High activities of cell wall degrading enzymes (chitinase, lipase and protease) involved in the mycoparasitism were evaluated by the endophytic T. pinophilus. In conclusion, this study demonstrated that the endophytic T. pinophilus may be a promising biocontrol agent against phytopathogenic fungi instead of chemical fungicides.

Fungicidal activity of extracellular products of cyanobacteria against Alternaria porri

ABSTRACT Although cyanobacteria are recognized as renewable sources of biomass for bioactive compounds, they have received little attention as potential biocontrol agents of foliar plant diseases. The purpose of this study was to evaluate the fungicidal efficacy of cyanobacterial extracellular products against Alternaria porri, which causes onion purple blotch disease, in vitro and under greenhouse conditions. Among the tested cyanobacteria (Anabaena oryzae, Arthrospira sp., Nostoc minutum, N. muscorum and Oscillatoria sp.), extracellular metabolites of N. muscorum and Oscillatoria sp. reduced the linear growth of A. porri by 20.37 and 36.34%, respectively. Culture filtrates of both Oscillatoria sp. and N. muscorum contained high concentrations of phenolic compounds (104.33 and 145.0 mg l−1, respectively), and alkaloids (473.31 and 378.12 mg l−1, respectively). GC-Mass analysis revealed that the most prevalent component in culture filtrates of N. muscorum and Oscillatoria sp. was beta ionone (7.21 and 7.17% of total analytes, respectively). Norharmane and α-iso-methyl ionone constituted 7.08 and 6.83% in N. muscorum and Oscillatoria sp., respectively. Components identified in the two culture filtrates included piperazine derivatives, isocyclocitral, α-trans-seequicyclocitral, phytol, oleic acid, fatty acids esters (methyl palmitate and linoleic acid mythyl ester), myristic alcohol and palmityl chloride. Application of culture filtrates of N. muscorum and Oscillatoria sp. under greenhouse conditions reduced disease severity by 55.1–66.5%. In conclusion, extracellular metabolites of N. muscorum and Oscillatoria sp. have potential as effective fungicides to control purple blotch disease of onion.

First Report of Bacterial Wilt Caused by Ralstonia solanacearum Biovar 2 Race 1 on Tomato in Egypt.

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.

Peroxidase and Polyphenoloxidase Activities as Biochemical Markers for Biocontrol Efficacy in the Control of Tomato Bacterial Wilt

Peroxidase and Polyphenoloxidase Activities as Biochemical Markers for Biocontrol Efficacy in the Control of Tomato Bacterial Wilt We have studied the effect of certain bioagents for the control of bacterial wilt of tomato under greenhouse and field conditions and the effect of these bioagents in induction of some enzyme activity in planta e.g. Peroxidase (PO) and polyphenoloxidase (PPO). Under greenhouse conditions the effect of Pseudomonas putida and P. fluorescens, and their combination were studied, and we found that both of them reduced the disease 60 and 66.67%, respectively and the combination treatment reduced the disease 53.33%. Also under field conditions P. putida was the best in reduction of the disease followed by the combination and then P. fluorescens. The P. fluorescens treatment recorded the highest percent yield increase in the two trails.