Efficacy of biological therapies against onion basal rot caused by Fusarium oxysporum f. sp. cepae under field and storage conditions

Résumé

Basal rot disease of onion is caused by Fusarium oxysporum f. sp. cepae (Hans.) (FOC) economically significant losses wherever onion is grown.  Fusarium oxysporum were isolated from diseased onion cultivated in different places of Assiut, Egypt. Efficacy of certain yeasts was evaluated for controlling the basal rot of onion in vitro. Among of the tested isolates, Saccharomyces cerevisiae gave the greatest inhibition (57.74%) and Candida tropicalis (1) significantly exerted the greatest reduction of mycelial growth of F. oxysporum f. sp. cepae (51.18%). Based on the in vitro screening, effective yeasts were evaluated under greenhouse, field and storage conditions. Yeasts were applied by two methods (add the pathogen and antagonistic yeasts to soil before sowing seedling onion, and seedling onion soaking in yeasts for 20 minute). Both methods of inoculation showed substantial impact on disease development and plant growth. Add method caused maximum reduction in plant germination, followed by soaking method as compared to control. Application of fungicide (Captain) as compared brought a remarkable increase in seedling emergence of treated plants inoculated with F. oxysporum as compared to the untreated plants. In conclusion, tested yeasts were useful as an alternative to chemical control of the onion basal rot and to enhanced growth and yield of onion.