Department of Plant Pathology and Entomology, College of Agriculture, University of Tehran, Karaj, Iran Genetic Diversity Among Iranian Isolates of Rhizoctonia solani Ku¨hn Anastomosis Group1 Subgroups Based on Isozyme Analysis and Total Soluble Protein Pattern M. M. Mohammadi Mohammadi 1 , M. M. Banihashemi Banihashemi 1 *, G.-A. G.-A. Hedjaroude Hedjaroude 1 and and H. H. Rahimian Rahimian 2 AuthorsÕ addresses: 1 Department of Plant Pathology and Entomology, College of Agriculture, University of Tehran, Karaj 31587-11167, Iran; 2 Department of Plant Protection, College of Agriculture, University of Maˆzandaran, Saˆri, Iran (correspondence to M. Mohammadi. E-mail: mohamadi@ut.ac.ir) With 2 figures Received January 4, 2002; accepted January 6, 2003 Keywords: Anastomosis group, cluster analysis, electrophoretic phenotype, isozyme pattern, mycelial protein profile, Rhizocto- nia solani Ku¨hn, similarity matrix Abstract Rhizoctonia solani is a destructive fungal pathogen with a wide host range. The R. solani complex species includes several divergent groups delimited by affinit- ies for hyphal anastomosis. In this study, genetic vari- ation among 20 isolates of R. solani anastomosis group 1 (AG1) subgroups (AG1-IA and AG1-IB) col- lected from Maˆzandaran province, Iran, and standard isolates of these subgroups, was determined by iso- zyme analysis and total soluble protein profile. Mycelial protein pattern and isozyme analysis were studied using denaturing and non-denaturing poly- acrylamide gel electrophoresis, respectively. A total of 15 enzyme systems were tested, among which six enzymes including esterase, alkaline phosphatase, superoxide dismutase, octanol dehydrogenase, lactate dehydrogenase and mannitol dehydrogenase generated distinct and reproducible results. The soluble protein patterns were similar among the R. solani isolates examined; however, minor differences in banding pat- tern were observed between the two subgroups. In isozyme analysis, a total of 64 electrophoretic pheno- types were detected for all six enzymes used. Based on cluster analysis and similarity matrix, the fungal isolates were divided into two genetically distinct groups of I and II consistent with the previously reported AG1-IA and AG1-IB subgroups in AG1. Group I represented all isolates belonging to AG1-IA subgroup, whereas group II represented all isolates belonging to AG1-IB subgroup. Results from isozyme analysis suggest that the subgrouping concept within AGs is genetically based. Introduction Rhizoctonia solani Ku¨hn (teleomorph: Thanatephorus cucumeris (A. B. Frank) Donk) is a highly heterogene- oussoil-bornefungalpathogenthatiscapableofinfect- ing a broad spectrum of plant species and causing diseases such as seed decay, damping off, stem and crown canker, root and fruit rot, and leaf and sheath blight. Because of its saprophytic competitiveness, pathogenicityandalmostunlimitedhostrange, R. solani is known as a ubiquitous species and has become one of the most important economic phytopathogens worldwide (Carling, 1996). Therefore, understanding the population genetics of the pathogen becomes vital vis-a-vis an efficient and sound disease management (Martin and English, 1997). Rhizoctonia solani has been studied intensively with respect to morphological (Armentrout et al., 1986; Kuninaga, 1986; Sneh et al., 1991), biochemical (Mordue et al., 1989; Laroche et al., 1992; Ueyama et al., 1993) and molecular (Liu et al., 1990; Liu and Sinclair, 1992a,b; Duncan et al., 1993; Liu and Sinclair, 1993; Liu et al., 1995; Kuninaga, 1996; Carling et al., 2002) characteristics in the last several decades. Despite these achievements, the taxonomy of this fungus remains somewhat ambiguous due to a considerable diversity in morphological properties, ecology, patho- genicity, host range, distribution and the lack of fossil records. Thus far, a total of 14 anastomosis groups (AG), AG-1-AG-13 and AG-BI (the bridging isolate AG), have been described for R. solani, all belonging to Rhizoctonia with multinucleate hyphal cells, a sexual form of Thanatephorus and asexual form of R. solani (Ogoshi et al., 1990; Carling, 1996; Carling, 2000; Carling et al., 2002). Based on colony morphology, host range, symptom development on host plant and *Present address: Sugar beet Seed and Plant Improvement Research Institute, AREEO, Ministry of Agriculture, Maˆhdasht Road, Karaj, Iran. U. S. Copyright Clearance Centre Code Statement: 0931–1785/2003/1513–0162 $ 15.00/0 www.blackwell.de/synergy J. Phytopathology 151, 162–170 (2003) Ó 2003 Blackwell Verlag, Berlin ISSN 0931-1785