Identification of phytopathogenic fungus causing rot on shallot bulbs (Allium ascalonicum) grown in Ninh Thuan during storage

Abstract

    Bulb rot causes serious losses in yield and quality of shallot during storage. The research aims at identifying the fungus causing post-harvested shallot rot. In this study, based on Koch's postulates, morphological characterization and molecular identification, two isolations of phytopathogenic fungus that caused bulb rot of shallots grown in Ninh Thuan were identified as Fusarium oxysporum and Aspergillus spp.. The disease starts from the roots or the scales near the base of shallot bulbs and spreads to the inside. The shallot rot shows symptoms of gradually turning brown, soft, and succulent. The results of pathogenic test showed that there were two strains of fungi that are capable of causing shallot rot. Analysis of the DNA sequences encoding the 18S rRNA region of those two fungal strains showed a similarity of over 99 % with F. oxysporum and Aspergillus spp. on Gen Bank. The results are the base for further research in preventing and tackling the disease, thus improving shallot preserving efficiency.