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Forty-two isolates of Rhizoctonia spp. were obtained from onion in Amasya, Turkey. Of these, 29% were Rhizoctonia solani (AG-4), 69% were Waitea circinata var. zeae (Rhizoctonia zeae) and 2% were binucleate Rhizoctonia (AG-B). Most of the isolates were recovered from rhizosphere soil. In pathogenicity tests on onion, R. solani AG-4 caused the greatest disease severity, those of W. circinata var. zeae were moderately virulent but binucleate Rhizoctonia isolates were of low virulence. This is the first report of binucleate Rhizoctonia AG-B and W. circinata var. zeae occurring on onion in Turkey.www.blackwell-synergy.com

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IntroductionMany coccoid algae are very difficult to identify because of their extremely small size and simple morphology, and they have been referred to as "little green balls" (Callieri and Stockner, 2002). These little green balls have often been reported as Chlorella Beijerinck or Chlorella vulgaris Beijerinck (Fawley et al., 2004). Since C. vulgaris "Beijerinck strain" (SAG 211-11b) was first described and isolated in axenic culture about 120 years ago, Chlorella strains have been used as model organisms in plant physiology and biochemical research (Burja et al., 2001). Furthermore, mass cultures of Chlorella have been used in agriculture as a single cell protein both for humans and animals, in biotechnology as recovery agents for waste treatment, and in biofuel technology as microbial energy producers (Golueke and Oswald, 1964;Fogg, 1971;Soeder, 1976;Abbott and Cheney, 1982).Among the over 100 traditionally defined Chlorella species, a lack of morphological characters led to the adoption of various approaches, including several combinations of physiological, biochemical, and serological studies, for identifying Chlorella species (John et al., 2003). The morphologically-defined species are considered very artificial and house many cryptic taxa. Using molecular data, Huss et al. (1999) demonstrated that only 5 "true" species could be regarded as part of the genus Chlorella. Materials and methods Chlorella isolationsEnvironmental water samples were taken from the