Characterization and intraspecific variation of Fusarium semitectum (Berkeley and Ravenel) associated with red-fleshed dragon fruit (Hylocereus polyrhizus [Weber] Britton and Rose) in Malaysia

Abstract

A total of 79 isolates of Fusarium semitectum were characterized by morphological and IGS-RFLP analysis to assess its intraspecific variation. Based on morphological characteristics, the isolates of F. semitectum were classified into 2 distinct groups, morphotypes I and II. Morphotype I was characterized by longer macroconidia (3 - septate: 31.03 ± 2.57 ìm; 5 - septate: 40.17 ± 1.85 ìm), 0 - 7 septate with 5 - septate was the most common, absence of chlamydospores, presence of sporodochia, abundantfloccose mycelium, peach colony appearance, peach to orange pigmentations and fast growing. While isolates of morphotype II produced shorter macroconidia (3 - septate: 24.98 ± 1.87 ìm; 5 - septate: 35.24
± 2.07 ìm), 0 - 5 septate with 3 - septate was the most common, with (56%) or without chlamydospores (44%), without sporodochia, abundant-floccose and abundant-powdery mycelium, beige to brown colonies, brown to dark brown pigmentations and slow growing. Corresponding to the morphological characterization, IGS-RFLP analysis indicated that the 79 isolates could be divided into 2 different clusters assigned as RFLP groups I and II. 49 IGS haplotypes were produced by 8 restriction enzymes
(AluI, Bsu15I, BsuRI, Eco881, Hin6I, MspI, PstI and TaqI) which indicated a high level of intraspecific variation and polymorphism among the 79 isolates. This is the first report of F. semitectum associated with H. polyrhizus.