This study was undertaken to determine the sensitivity of grape downy mildew (DM, Plasmopara viticola) and powdery mildew (PM, Erysiphe necator) to commonly used single-site fungicides in Virginia and nearby states. DM and PM isolates were collected from 2005 to 2007. In grape leaf disc bioassays, 92% of the DM isolates were QoI (azoxystrobin)-resistant, but none were resistant to mefenoxam. Eighty-two percent of the PM isolates were QoI-resistant, but none were resistant to boscalid and quinoxyfen. The frequency of the G143A point mutation, which confers high levels of QoI resistance, was quantified in DM and PM isolates by real-time PCR. Most of the QoI-resistant DM and PM isolates contained >95% of the 143A allele. QoI-sensitive DM isolates contained less than 1% of 143A. One out of 145 and 14 out of 154 QoI-resistant DM and PM isolates (able to grow on azoxystrobin concentration ï ³ 1 µg/ml), respectively, contained less than 1% 143A. Most PM isolates exhibited reduced sensitivity to five DMI fungicides when compared to a sensitive subgroup (n=9) and compared to published reports for unexposed populations; the resistance factor (median EC50 of the entire isolate collection divided by median EC50 of sensitive subgroup) was highest for tebuconazole (360) and myclobutanil (350), followed by triflumizole (79), triadimefon (61), and fenarimol (53). Sensitivities to all five DMI fungicides, but also azoxystrobin, were moderately to strongly correlated (pairwise r-values ranging from 0.60 to 0.88). / Master of Science in Life Sciences

Substanzen, die durch ihr hormonell wirksames Potenzial mit dem Hormonsystem interagieren und adverse Effekte auf die Reproduktion von Invertebraten und Vertebraten ausueben koennen, erlangten in den letzten Jahrzehnten große Aufmerksamkeit. Viele dieser Substanzen reduzieren die Fertilitaet oder die Fekunditaet, fuehren zu Abnormalitaeten in der Ontogenese oder im Verhalten der Tiere und haben Einfluss auf die Geschlechterverhaeltnisse. In der vorliegenden Arbeit wurden verschiedene Aspekte dieses Themengebietes bearbeitet. Das in Europa endemisch vorkommende Rotauge (Rutilus rutilus), ein Sueßwasserfisch, wurde als Modelltier fuer den Nachweis von (anti)androgenen Effekten auf aquatisch lebende Organismen etabliert. Zum Nachweis der (anti)androgenen Wirkmechanismen wurden die Tiere mit Modellsubstanzen aus drei verschiedenen Gruppen exponiert. Aus der Gruppe der Substanzen mit potenziell androgener Wirkung wurden Triphenylzinn (TPT) und Methyltestosteron (MT) verwendet, aus der Gruppe der Antiandrogene Vinclozolin (VIN) und Cyproteronazetat (CYP) und aus der Gruppe der Aromatasehemmer, und somit potenziell androgener Wirkung, Letrozol (LET) und Fenarimol (FEN). Feedbackmechanismen auf die Hypothalamus-Hypophysen-Gonaden-Achse (mRNA-Expression des Luteinisierenden Hormons, des Follikel stimulierenden Hormons und der Aromatase), mRNA-Expression potentieller Biomarker in der Leber (Androgen-Rezeptor-mRNA, Oestrogen-Rezeptor-mRNA), Sexsteroidspiegel im Blutplasma (17beta-Oestradiol und 11-keto-Testosteron), Enzymaktivitaeten im Gehirn (Aromatase), Histologie der Gonaden, Totallaenge, Gewicht und Geschlechterverteilung wurden als Endpunkte analysiert, um adverse Effekte auf die Reproduktionsbiologie von R. rutilus zu zeigen. Die untersuchten Endpunkte eigneten sich sehr gut zum Nachweis verschiedener Wirkmechanismen. / Substances that are able to interact with the endocrine system and cause adverse effects on the reproduction of invertebrates and vertebrates have gained much attention over the last few decades. Many of these substances reduce fertility or fecundity, lead to developmental abnormalities or abnormalities in the behaviour of animals and have an impact on sex ratios. The present study examines various aspects of these topics. The roach (Rutilus rutilus), a freshwater fish endemic in Europe, was established as a model animal for the detection of (anti)androgenic effects on aquatic organisms. For examination of the (anti)androgenic action, the animals were exposed to model compounds from three different groups: triphenyltin (TPT) and methyltestosterone (MT) from the group of substances with potentially androgenic effect, vinclozolin (VIN) and cyproteronacetate (CYP) from the group of antiandrogens, and letrozol (LET) and fenarimol (FEN) from the group of aromatase inhibitors, which thus have a potentially androgenic effect. Feedback mechanisms on the hypothalamus-pituitary-gonad-axis (mRNA expression of luteinising hormone, follicle stimulating hormone and aromatase), mRNA expression of potential biomarkers in the liver (androgen receptor mRNA, oestrogen receptor mRNA), steroid levels in the blood plasma (17beta-oestradiol and 11-ketotestosterone), enzyme activity in the brain (aromatase), histology of the gonads, total length, weight and sex ratios were analysed as endpoints to show adverse effects on the reproductive biology of R. rutilus. The studied endpoints are suitable for the detection of different modes of action. The histological examination of the gonads proved to be especially sensitive with the exposure to AACs to resulting in fundamental adverse damages to the gonads. It was ascertained that - in the early stages of ontogeny - androgens play as crucial of a role in the development of the gonads as previously attributed primarily to oestrogens.