37 Fusarium isolates (F. culmorum 20, F. graminearum 4, F. avenaceum 3, F. solani 4, and F. equiseti 6 from wheat, rye and triticale) were examined for pathogenicity and tested for zearalenone (F‐2) and trichothecenes production in vitro. Strong pathogens (F. culmorum and F. graminearum) produced deoxynivalenol and 3‐acetyl‐deoxynivalenol and zearalenone in considerable quantities.

The importance of root and spore surface molecules in the interactions of Fusarium spp. with conifer roots, and cellular localization of proteins presumed to be involved in host defence, were investigated. For adhesion studies, using a combination of fluorescein isothiocyanate (FITC) labelled lectins and high perfomance liquid chromatography (HPLC), several sugars (pinitol, xylitol, galactose, mannose, and glucose) were detected in root surface mucilage. Both artificial substrata and detached living roots were used to evaluate the significance of selective removal of root or spore surface components on the adhesion process. The spores or roots were pretreated with either periodic acid, pronase E, potassium hydroxide or diethyl ether. Pretreatment of the spores with diethyl ether reduced significantly the level of spore adhesion, which suggests that the adhesive component is either a lipid, or is bound to lipid. Since oxidation of carbohydrate reactive sites with periodic acid on the root surface almost completely abolished the development of germ tubes by adherent spores, it was presumed that some of these periodate-sensitive substances serve as a nutrient source for the fungus. On inoculated roots, F. avenaceum and F. culmorum were significantly pathogenic to both Norway spruce and Scots pine seedlings. Cytochemical labelling of sites of accumulation of host defence molecules within infected root tissues using anti-peroxidase demonstrated increased peroxidase activity in host cell walls. With anti-chitinase and anti-glucanase, gold labelling was found mainly on pathogen hyphal walls.Key words: conifer seedlings, adhesion, Fusarium spp., PR proteins, immunolocalization, lectins.

Thirty-eight isolates of Rhizoctonia spp. were isolated from Scots pine (Pinus sylvestris) seedlings with damping-off symptoms, originating from two forest nurseries in central-west Poland (Wronczyn and Jarocin) and from diseased seedlings grown in soil from Wronczyn nursery. Majority of these isolates (79%) had multinucleate cells and were identified as Rhizoctonia solani. The remaining isolates were recognized as binucleate Rhizoctonia spp. R. solani isolates were characterized using hyphal anastomosis and were divided into five anastomosis groups (AG). The most prevalent was AG5 (37% of isolates), followed by AG2-1 (30%) and 27% of the isolates were identified as AG4. Groups AG1-IB and AG2-2 were only represented by single isolates. The virulence recorded as mortality (in percentage) was comparatively high for binucleate and multinucleate isolates of Rhizoctonia spp. Sequence analysis of the polymerase chain reaction (PCR)-amplified internal transcribed spacer (ITS) rDNA region was used for phylogenetic analysis. The dendrogram showed that isolates were distinctly separated based on their AG types and there was no relationship between pathogenicity on Scots pine seedlings and the AG to which the isolates belong to. The results are discussed with respect to pathogenic potential of the various AG groups.

Fusaria isolates from wheat, barley and corn — pathogenic to seedlings, were found to be able to to produce zearalenone. Several pathogens, mainly of F. culmorum (W. G. Sm.) Sacc. species, synthesized high yields of zearalenone: 50–700 mg/kg of kernels. Weak and nonpathogenic isolates did not produce zearalenone (or very small amounts).

Taxonomy, toxinogenicity and pathogenicity of 26 isolates of Fusarium‐Sporotricbiella section were studied. Strains of Fusarium sporotrichioides Sherb. isolated in Poland from cereals have been found severely pathogenic towards cereal seedlings. They produced significant amounts of T‐2 toxin (up to 600 mg/kg) and other trichothecenes under laboratory conditions. The investigated strains of F. tricinctum (Corda) Sacc. and F. poae (Peck) Wollenw. proved to be nonpathogenic and nontoxigenic under the same conditions. Zusammenfassung Fusarium sporotrichoides Sherb., F. tricinctum (Corda) Saco und F. poae (Peck) Wollenw. — Kulturmerkmale, Toxinogenität und Pathogenität gegenüber Getreide Untersucht wurde die Taxonomie, Toxinogenität und Pathogenität von 26 Fusarium‐lsolaten aus der Sporotrichiella‐Sektion. Fusarium sporotnchoides‐Sümme, die von Getreide in Polen isoliert wurden, zeigten sich als sehr pathogen gegenüber Getreidesämlingen. Unter Laborbedingungen produzierten diese Stämme bedeutende Mengen an T‐2 Toxin (bis zu 600 mg/kg) und anderen Trichothecenen. Die untersuchten F. tricinctum‐ und F. poae‐Sämme zeigten sich unter den gleichen Bedingungen als nicht pathogen und nicht toxinogen.