Full Length Research Paper

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

M. Masratul Hawa*, B. Salleh and Z. Latiffah

School of Biological Sciences, University Sains Malaysia, 11800 Penang, Malaysia.

*Corresponding author. E-mail: masratulhawa1984@yahoo.com. 

Tel.: +6012-5311945. Fax: +604-6565125.

Accepted 6 August, 2009

   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 µm; 5 - septate: 40.17 ± 1.85 µm), 0 - 7 septate with 5 - septate was the most common, absence of chlamydospores, presence of sporodochia, abundant-floccose 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 µm; 5 - septate: 35.24 ± 2.07 µm), 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.

Key words: Fusarium semitectum, Hylocereus polyrhizus, IGS-RFLP, intraspecific variation, morphology.