Abstract

To investigate the genetic relationship among 12 species belonging to the Fusarium section Martiella, Dlaminia, Gibbosum, Arthrosporiella, Liseola and Elegans, the internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) were amplified with primer pITS1 and pITS4 using the polymerase chain reaction (PCR). After the amplified products were digested with 7 restriction enzymes, restriction fragment length polymorphism (RFLP) patterns were analyzed. The partial nucleotide sequences of the ITS region were determined and compared. Little variation was observed in the size of the amplified product having sizes of 550bp or 570bp. Based on the RFLP analysis, the 12 species studied were divided into 5 RFLP types. In particular, strains belonging to the section Martiella were separated into three RFLP types. Interestingly, the RFLP type of F. solani f. sp. piperis was identical with that of isolates belonging to the section Elegans. In the dendrogram derived from RFLP analysis of the ITS region, the Fusarium spp. examined were divided into two major groups. In general, section Martiella excluding F. solani f. sp. piperis showed relatively low similarity with the other section. The dendrogram based on the sequencing analysis of the ITS2 region also gave the same results as that of the RFLP analysis. As expected, 5.8S, a coding region, was highly conserved, whereas the ITS2 region was more variable and informative. The difference in the ITS2 region between the length of F. solani and its formae speciales excluding F. solani f. sp. piperis and that of other species was caused by the insertion/deletion of nucleotides in positions 143-148 and 179-192.

• Keywords: rDNA; internal transcribed spacer (ITS); PCR; restriction fragment length polymorphism; Fusarium; se