الفهرس 
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Abstract
Onion Black-mould and neck-rot are the most important diseases during storage. This work was carried out to achieve safe method(s) to control either diseases and to improve store ability of onion bulbs. The obtained results could be summarized as following: 1. Apergillus niger is the causal organism of black mould disease while Botrytis allii causes neck-rot disease. 2. Both fungi were pathogenic to Giza-20 onion cultivar and Gharbia isolates (G1A & G1B) of the pathogens were more aggressive. 3. Salicylic acid, Oxalic acid and Potassium monohydrogen phosphate reduced the growth of A. niger and B. allii than control, significantly. Salicylic acid showed the best effect and increasing the concentration of any tested chemical inducer showed better efficiency in reducing the mycelial growth. 4. Tested volatile oils reduced the mycelial growth of the pathogens significantly. Thyme oil showed the best effect while fennel oil resulted the least effect. In all cases ; increasing the concentration of any tested oil gave better results of mycelial growth inhibition. 5. Water plant extracts reduced the growth of the tested pathogens, than control, significantly. Neem extract showed the best effect and the vice was versa with eucalyptus one. 6. All tested biocontrol agents significantly inhibited the growth of A. niger and B. alii than control. The best inhibitory effect was due to Trichoderma harzianum followed by T. hamatum and Arcanobacterium bernardiae. 7. The tested biocontrol agents decreased the incidence of black mould and neck-rot diseases in storage up to 4 months. These reductions were significantly, than control, when T. harzianum, B. subtilis, T. hamatum and / or A. bernardiae were individually applied. Ridomil gold plus fungicide showed more efficiency in either diseases reduction. 8. Chemical inducers decreased the incidence of either black mould or neck-rot diseases than control, significantly. Increasing the concentration of any compound showed more efficiency of diseases reduction and twice applications of any compound gave better results of diseases reduction than did an application. In general, Salicylic acid was the best tested inducer while potassium mono hydrogen phosphate was less effective. 9. Thyme oil was more effective in reducing the incidence of both diseases under study while fennel oil showed less efficiency. Increasing the applied dose of any tested oil gave significant results of the diseases reduction. 10. Water plant extracts decreased the incidence of black mould and neck-rot diseases than control; significantly. Neem extract followed by Basil one gave the best results; while marjoram and eucalyptus extracts were less effective. 11. Shandwell onion cultivar showed the least susceptibility to both pathogens while Behairy cultivar was the most susceptible. Giza 6 and Giza 20 cultivars could be considered as moderately susceptible to black mould and neck-rot diseases. 12. Compost application to the soil gave better results of reducing black mould disease than did Actosol preparations. While Actosol-macroelements and / or compost in reducing neck-rot infection during storage. 13. Tested chemical inducers, volatile oils and Ridomil gold plus fungicide sharply decreased total soluble sugars (TSS) in onion plants than control. Salicylic acid caused the most reduction and Oxalic acid gave the least reduction. 14. All tested chemical inducers, plant oils; except fennel one and Ridomil increased the activity of peroxidase, polyphenol oxidase and chitinase than control; significantly.