Characterization and sustainable management of Aspergillus welwitschiae-induced black rot in Egyptian garlic

Black rot is a significant postharvest disease that poses a major threat to garlic (Allium sativum L.) production globally. In Egypt, the disease has been frequently observed in garlic cultivars Balady and Sids-40. This study aimed to accurately identify the causal agent of black rot symptoms in marketed garlic and propose an effective control strategy. Several isolates of black aspergilli were obtained from symptomatic garlic bulbs, and the representative isolate, SHAMS-18, was subjected to detailed morphological and molecular characterization. Molecular identification using fungal DNA barcoding confirmed the pathogen as Aspergillus welwitschiae. Pathogenicity tests on healthy garlic bulbs validated the virulence of A. welwitschiae, and the pathogen was successfully re-isolated, fulfilling Koch’s postulates. This marks the first report of A. welwitschiae as a postharvest pathogen of garlic in Egypt. To mitigate this issue, we developed an eco-friendly control method involving chitosan and gum arabic coating, which significantly reduced the development of black rot symptoms on inoculated peeled garlic cloves. Our findings present the accurate identification and sustainable management of black rot in garlic, offering a viable solution for enhancing garlic storage and reducing postharvest losses.