The microelements boron, iron and zinc were tested for their effect on the incidence of onion basal rot caused by Fusarium oxysporum f.sp. cepae (FOC) and Fusarium solani (FS). The tested microelements inhibited mycelial growth and spore germination of the causal pathogens and their counts in the soil and rhizosphere of onion plants. In field experiments, the results of the two seasons indicated that spraying of microelements resulted in significant reduction to the disease during stoage with significant increas to bulbs yield and their diameter. Generally, spraying with the tested microelements at the rate of 50 g/ 100L.water was more effective in reducing onion basal rot than 100 g/100L.water.
The percentages of onion basal rot after five months of bulb storage were determined. In storage experiments, results indicated that boron was the least effective in reducing the disease, which resulted in 19.75% disease infection, on the average at the rate of 50 g/100L.water. On the other hand, iron treatment was the most effective one in this respect 10.0%, on the average followed by zinc 11.25%, on the average during 2008/2009 and 2009/2010 growing seasons. The activity of the oxidative enzymes, i.e., peroxides and polyphenol-oxidase and phenolic compounds were higher in treated onion plants by the microelements compared with control.