Effect of Storage Conditions on the Development of Onion Bulb Rot (Allium cepa L.) in Calabar, Nigeria

Abstract

Aims: An investigation was carried out to isolate and identify the fungal pathogens responsible for post-harvest (storage) deterioration of onion bulbs in the North, Central, and Southern Senatorial Districts of Cross River State, Nigeria. Study Design: The experiment was arranged in a Completely Randomized Block Design (CRBD), with different fungal isolates serving as the treatments and various onion species as the blocks. Place and Duration of Study: Calabar in Nigeria's South-South zone. The study was conducted from June to July 2025. Methodology: Infected onion bulbs were randomly collected from three markets in each of the three zones of Cross River State to isolate the pathogens responsible for the rots on the affected bulbs. To test the effect of storage methods on disease development, white and purple onion bulb species inoculated with the isolated fungi were stored under different conditions: basket, bag, and floor to determine the disease severity of the different onion species. Results: The result of the inoculated onion bulb clearly showed that Rhizopus stolonifer, Botrytis sp., and Fusarium sp. recorded a significant (P0.05) higher disease severity on white onion bulbs. However, the control, in general, was significantly (P≤0.05) lower on white and purple onions and differed among the storage methods. The purple onion bulb showed a significantly (P≤0.05) greater increase in rot severity on A. flavus in bags and on the floor than on A. fumigatus in baskets. Comparing means was used to determine the best storage method. Meanwhile, a significantly higher mean value of 37.81% was recorded by the floor storage method for the white onion bulb. In contrast, the purple onion bulb did not show any difference among treatments (P ≥ 0.05). The pathogenicity test revealed that all the isolated fungi were pathogenic to the onion bulbs (both white and purple). Conclusion: Based on the results, the floor storage method is the best, and it is strongly recommended to adopt effective storage methods to minimize storage losses.