Identification of Fusarium spp., the causal agent of twisted disease of shallot

Shallot is key horticultural species in Indonesia. Shallot productivity is declining due to pests and diseases and the use of low-quality seeds. One of the most important diseases affecting shallot is twisted disease. This study aimed to identify the pathogen responsible for causing twisted disease using molecular techniques and to investigate the pathogenicity of Fusarium isolates in a pot trial. Field surveys of twisted disease were conducted in some provinces in Indonesia, i.e., Batu and Nganjuk (East Java), Kulon Progo, Bantul, Gunung Kidul and Sleman (Yogyakarta), Temanggung, Pemalang and Brebes (Central Java), Cirebon (West Java) and Enrekang (South Sulawesi). A total of 44 Fusarium isolates were obtained from diseased bulb samples. Pathogenicity tests showed that all 44 Fusarium spp. isolates were capable of infecting shallot with disease incidence ranging from 11.11 to 100%. Molecular identification using ITS primers showed 75, 18 and 7% of the isolates were Fusarium solani, Fusarium acutatum and Fusarium oxysporum, respectively. Results from the pathogenicity assay and molecular identification indicated that the wilting symptom of shallot could be caused by F. solani and F. acutatum, while bulb rot could be caused by F. solani, F. acutatum or F. oxysporum, and twisted disease could be caused by F. solani or F. acutatum.