Ismail R. Abdel-Rahim

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.

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.

Effect of Certain Plant Extracts to Control Purple Blotch Disease of Onion Plants (Allium cepa L.)

The present investigation aimed to isolate the causative agents of onion purple blotch disease and evaluate the efficacy of certain plant extracts against the pathogen in vitro and under greenhouse condition. 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 well diffusion technique. The data indicated that there were significant differences between these extracts in their effect on fungal growth of Altenaria porri and the best were A. indica and D. stramonium. Under greenhouse condition the application of aqueous extract of A. indica either before or after 48h of A. porri inoculation, produced the highest reduction in disease severity comprising 70% and 74.7% respectively. According to our results it can be concluded that plant extracts of A. indica and D. stramonium can be used for the management of purple blotch disease in onion.

Fungi-induced paint deterioration and air contamination in the Assiut University hospital, Egypt:

This study aims to evaluate the correlation between fungi causing paint deterioration and air contamination in Assiut University hospital to give a complete picture for the fungal quantity and spectrum. Seventeen fungal species were isolated from 15 samples of deteriorated water-based paint collected from the hospitals. Chaetomium globosum was the most common paint-deteriorating fungal species, followed by Alternaria alternata, Aspergillus parasiticus, Penicillium oxalicum and Setosphaeria rostrata. Direct examination confirmed the ability of these fungi to colonize the paint samples producing mycelia, conidia and fruiting bodies. In vitro, these fungi exhibited high potential to utilize the thin layer of polyacrylic paint and significant enzymatic activities of cellulase, lipase and urease that may play a main role in paint degradation and as virulence factor of human diseases. Moreover, 27 fungal species were isolated as air contaminating mycobiota. Aspergillus spp., Cladosporium cladosporioides, P. oxalicum, A. alternata and C. globosum caused a considerable amount of indoor air contamination. The results indicated that there is a clear correlation between fungi causing paint deterioration and air contamination, whereas certain fungi were responsible for wall paint deterioration and frequently indoor air contamination. The current study suggests that improvement of antimicrobial additives of paints may be a promising approach to reduce paint biodeterioration and subsequently air contamination of indoor environments.