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  • Author or Editor: A. Lebeda x
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The occurrence of sexual compatibility types (mating types) was studied in a set of 59 Bremia lactucae isolates originating from 33 naturally infected and wild populations of Lactuca serriola (prickly lettuce) plants occurring in the Czech Republic, Germany and France. The isolates were collected in the period 1997-1999 as part of detailed population studies of virulence structure. Both compatibility types (B1 and B2) were recorded. However, the majority of the isolates was determined as type B2, with only two isolates being type B1. The reasons for and influence of this sexual structure are discussed in relation to the virulence of pathogen populations and interactions between wild and crop pathosystems. Occurrence of natural sexual reproduction of B. lactucae on L. serriola plants was extremely rare. Virulence variation of B. lactucae populations occurring on L. serriola would not seem to be related to sexual reproduction.

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Fourteen isolates of tomato powdery mildew (Oidium neolycopersici) and one isolate of the following species: Podosphaera fusca (= Sphaerotheca fusca), Erysiphe orontii (cucumber powdery mildews), Erysiphe cicho­ra­cearum (lettuce powdery mildew) and Erysiphe aquilegiae var. ranunculi (Ranunculus lingua powdery mildew) were used for com­parative morpho­logical studies. Basic characteristics of the anamorphs, including outer conidial wall patterns, were compared using light and scanning electron microscopy (SEM). In main morphological features, O. neo­lyco­persici was strongly differentiated from E. cichoracearum, E. orontii and P. fusca. However, based on morphological features (e.g. germination type; appres­sorium shape; morphology of conidiophores) O. neolyco­per­sici was close to E. aquilegiae var. ranunculi (both belong to Oidium subgen. Pseudo­idium) and it probably could be placed to Erysiphe sect. Erysiphe (= Erysiphe s. str.)

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We have investigated a method for direct astatine labeling of proteins. Binding sites for astatine were created by coupling of a nido-carborane derivative to a protein, the human epidermal growth factor (hEGF), using two different conjugation methods - by glutaraldehyde cross-linking or by introduction of sulfohydryl groups by Traut's reagent with subsequent linking of ANC-1 with m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester. The conjugates were astatinated using the Chloramine-T method in high yield. The best labeling was obtained by the glutaraldehyde conjugate with an average yield of 68±9%. In vitro stability tests indicated that the glutaraldehyde conjugated label was as stable as hEGF labeled with astatobenzoate.

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