Plant Pathol. J. 20(4) : 264-270 (2004) The Plant Pathology Journal The Korean Society of Plant Pathology Genetic Variation in Fusarium oxysporum f. sp. fragariae Populations Based on RAPD and rDNA RFLP Analyses Gopal Nagarajan, Myeong Hyeon Nam 1 , Jeong Young Song, Sung Joon Yoo 2 and Hong Gi Kim* Department of Agricultural Biology, Chungnam National University, Daejeon 305-764, Korea 1 Strawberry Experiment Station, Chungnam ARES, Nonsan 320-862, Korea 2 Bioshield Co. Ltd. HTVC KAIST, Daejeon 305-701, Korea (Received on September 13, 2004; Accepted on November 16, 2004) Fusarium oxysporum f. sp. fragariae is a fungal pathogen causing strawberry wilt disease. The random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphisms (RFLPs) of intergenic spacer (IGS) region of rDNA were used to identify genetic variation among 22 F. oxysporum f. sp. fragariae isolates. All isolates could be distinguished from each other by RAPD analysis and RFLP of 2.6 kb amplified with primer CNS1 and CNL12 for IGS region of rDNA. Cluster analysis using UPGMA showed eight distinct clusters based on the banding patterns obtained from RAPD and rDNA RFLP. These results indicate that F. oxysporum f. sp. fragariae isolates are genetically distinct from each other. There was a high level genetic variation among F. oxysporum f. sp. fragariae. Keywords : Fusarium oxysporum f. sp. fragariae, genetic variation, RAPD, rDNA, RFLP Strawberry (Fragariae X ananassa Duch.) is an economi- cally important crop. In recent years, strawberry production has shown worldwide increase (FAO Statistical Databases). However, Fusarium oxysporum Schlechtend.: Fr. f. sp. fragariae Winks and Williams, which causes strawberry Fusarium wilt disease, has dramatically decreased commer- cial strawberry production (Winks and Williams, 1965). The forma specialis causing wilt on strawberry has been designated as f. sp. fragariae (Wilhelm, 1984). Isolates that cause the disease in members of a particular family, genus, (or) species are formae speciales. Recently, molecular methods such as the PCR have been described to resolve genetic variation among isolates within or between formae speciales of F. oxysporum (McDonald, 1997). Especially, random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphisms (RFLPs) of rDNA have been widely used for assessing genetic diversity, genome mapping, and molecular diagno- stics of many fungal species (Annamalai et al., 1995; Manulis et al., 1994). Another strategy to detect genetic variation is the use of defined PCR amplified fragments as substrate for RFLP or sequence analysis. The ribosomal DNA (rDNA) regions have often been chosen for taxonomic and phylogenetic studies, because sequence data are available and contain both variable and conserved regions; despite the discrimi- nation at the genus, species, or intraspecific level. The rDNA repeat includes both highly conserved genes and more variable spacer regions. The spacer regions, including the internal transcribed spacer (ITS) and the intergenic spacer (IGS), have been used to examine relationships among more closely related taxa by analysis of RFLP analysis (Appel and Gordon 1995; Edel et al., 1995). The rDNA region analyses have been used successfully to differentiate other Fusarium species such as F. avenaceum, F. arthroporioides, and F. tricinctum (Yli-Mattila et al., 2002); and within the Fusarium formae speciales such as F. oxysporum f. sp. cyclaminis (Woudt et al., 1995), F. oxysporum f. sp. dianthi (Manicom et al., 1990), F. oxysporum f. sp. gladioli (Mes et al., 1994), and F. oxysporum f. sp. phaseoli (Woo et al., 1996). In this study, RAPD markers and RFLPs of IGS region of rDNA were used to ascertain the affinities and variation among F. oxysporum f. sp. fragariae isolates of infected strawberry. This study evaluated the genetic variation that could be useful for further resistance-breeding of straw- berry against this pathogen. Materials and Methods Isolates. Twenty-two isolates of F. oxysporum f. sp. fragariae were collected from different major strawberry-cultivating areas in Korea (Table 1). After pathogenicity test on strawberry (cultivar: Dochiodome), they were used for this investigation. Individual isolates were selected through the subculture of a single conidium. Genomic DNA extraction. Isolates were cultured on potato Mini-Review *Corresponding author. Phone) +82-42-821-5768, FAX) +82-42-823-8679 E-mail) hgkim@cnu.ac.kr