Genetic Variation and Phylogenetic Analysis of Fusarium Species Based on Sequencing of Internal Transcribed Spacer (ITS) Region

Abstract

     The Internal Transcribed Spacer (ITS) region is widely used for fungal identification in complex biological specimens. Fusarium is an opportunistic fungus responsible for a range of diseases in both plants and humans. This study aimed to identify Fusarium species at the species level and investigate their genetic variation. The ITS region of eighteen isolates was amplified by universal ITS primers (ITS1 and ITS4) using PCR. The PCR products of the ITS regions with a molecular weight of 588 bp were sent for sequencing, and then analyzed the sequence results by blast in the National Centre Biotechnology Information (NCBI) online to detect genetic variation in ITS regions. Phylogenetic analysis was compared with NCBI's reference sequences using MEGA X software. According to the NCBI GenBank database, four Fusarium species were first isolated in Iraq: F. pseudoanthophilum, F. fujikuroi, F. luffae, and F. boothii. Eleven isolates were identified as F. pseudoanthophilum (NR_163682.1) from the USA, with identities ranging from 98% to 100%. They were assigned the accession numbers MW577709-MW577719. Four isolates were identified as F. fujikuroi (NR_111889.1) from the USA, with identities ranging from 99% to 100%. They were assigned the accession numbers MW577720-MW577723. Two isolates were identified as F. luffae (NR_164594.1) from China, with an identity of 99%. They were assigned the accession numbers MW577724-MW577725. One isolate was identified as F. boothii (NR_121203.1) from the USA, with an identity of 99%. It was assigned the accession number MT658128.1. Thirty-five substitutions were detected by Bioedite software; most of them are deletions, accounting for 51.43%, followed by transitions, 31.43%, and transversions, 11.43%. These substitutions are found in most of the Fusarium spp—isolates, except for two isolates, which had no substitutions. The novelty of the present study lies in the first isolation of four Fusarium species in Iraq: F. pseudoanthophilum, F. fujikuroi, F. luffae, and F. boothii.