|Cotter, H van t|
Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/26/2005
Publication Date: 4/6/2006
Citation: Schmitt, M., Carzaniga, R., Cotter, H., O'Connell, R., Hollomon, D. 2006. Microscopy reveals disease control through novel effects on fungal development: a case study with an early-generation benzophenone. Pest Management Science. 62(5):383-392. Interpretive Summary: The Benzophenones are a new class of fungicides that effectively control powdery mildew infections of cereals and other crops. The precise biochemical mechanism by which they effect this control is different from all previously known mechanisms of action. This study uses microscopic observations of the effects of the new fungicide class on the growth and development of several powdery mildew crop pathogens to demonstrate that the Benzophenones cause a number of previously unseen abnormalities on the shape and development of the fungal pathogens. Since the Benzophenones also produce effects on the model fungus Aspergillus nidulans, where several known mutants produce analogous effects on fungal development, some hypotheses are proposed that relate to the potential mechanisms by which the Benzophenones might prevent crop infections by the pathogens. Benzophenones provide a further example of the benefits of whole-organism testing in the search for novel fungicide modes of action.
Technical Abstract: The benzophenones are a new class of agricultural fungicides that demonstrate protectant, curative, and eradicative/anti-sporulant activity against powdery mildews. The chemistry is represented in the marketplace by the fungicide Metrafenone, recently introduced by BASF as FLEXITY®.1 The benzophenones show no evidence of acting by previously identified biochemical mechanisms, nor do they show cross resistance with existing fungicides. The value of microscopy in elucidating fungicide mode of action is demonstrated through identification of the effects of an early benzophenone, eBZO, on mildew development. eBZO caused profound alterations in the morphology of both monocot and dicot powdery mildews, affecting multiple stages of fungal development including spore germination, appressorial formation, penetration, surface hyphal morphology, and sporogenesis. Identification of analogous effects of eBZO on sporulation in the model organism Aspergillus nidulans provides a unique opportunity to elucidate important morphogenetic regulatory sites in the economically important obligate pathogens, the powdery mildews. Benzophenones provide a further example of the benefits of whole-organism testing in the search for novel fungicide modes of action.