Onion bulbs were stored in the field, in piles until its commercialisation but the bulbs may be affected by fungal diseases. The objective was to assess the effects of the temperature (T), relative humidity (RH) within the piles, the water percentage (WP) and soluble solids (SS) of the bulbs over Aspergillus niger incidence. Bulbs of Cobriza INTA, Antártica INTA, Valcatorce INTA, Valuno INTA and Grano de Oro were storage in piles and T, RH, A. niger incidence, WP and SS were determined in bulbs periodically sampled. The incidence increased in the first stage of conservation, and the decreasing temperatures induced the fungal sporulation. When temperatures dropped below 14°C, the pathogen activity diminished because the detachment of affected scales. The WP and the SS were similar in coloured cultivars so they did not explain the incidence differences. The optimal conservation period ranged between two and three and a half months.
Keywords: postharvest, temperature, relative humidity, water percentage, soluble solids, cultivars, Aspergillus niger, onion bulbs, Allium cepa L