Transgenic plants are becoming a more powerful tool in modern biotechnology. Genetic engineering was used in biotech-derived products to create genetically modi ed (GM) plants. Plant bioreactor systems have proven to be extremely effective in the production of disease resistance plants. The onion (Allium cepa, L.) is a common, important perennial vegetable crop grown in Egypt for food and economic value. Onions are susceptible to a variety of fungal infections and diseases. Aspergillus niger is a common onion phytopathogen that causes diseases such as black mould (or black rot), which is a major issue, particularly when exporting onions. A.niger grows between the bulb's outer (dead, aky) skin and the rst eshy scales, which become water-soaked. Thionin genes produce thionin proteins, which have antimicrobial properties against a variety of phytopathogens, including A. niger. Chitosan nanoparticles act as a carrier for the thionin gene, which allows A. cepa to resist infection by A. niger. Transgenic A. cepa has a high level of resistance to fungal infection. Transgenic A. cepa had a 27 % weight inhibition compared to non-transgenic one, which had a 69 % inhibition. The expressed thionin protein has a 52 % inhibitory effect on A. niger spore germination. All of these ndings supported thionin protein's antifungal activity as an antimicrobial peptide. Furthermore, the data presented here demonstrated the e cacy of chitosan nanoparticles in gene transformation. The present study describes the bene ts of producing transgenic onion resistance to black rot diseases.positive control; (c) spores treated with transgenic thio-60 protein plant protein.