|Krasnoff, Stuart - USDA, ARS, ITHACA, NY|
Submitted to: CRC Press
Publication Type: Book / Chapter
Publication Acceptance Date: October 15, 1998
Publication Date: N/A
Technical Abstract: Our research concentrates on screening extracts from plants and insect-pathogenic fungi for novel pesticidal chemistries with high target selectivity and environmental compatibility. Our search is directed to narrowly defined relatively untapped biological niches We are also interested in improving techniques for extracting and quantifying known secondary metabolites to refine our understanding of the roles these compounds play in nature and agroecosystems and their potential roles in managing crop pests and diseases. Extracts of culture broth from an undescribed species of the fungal genus Aschersonia fungus, exhibited insecticidal activity in a per os assay against Drosophila melanogaster. Two new cyclic depsipeptides, Destruxins A4 and A5 were isolated by bioassay guided fractionation. These are the first biologically active metabolites reported from an Aschersonia. LC50 values against D. melanogaster were estimated at 41 (A4) and 52 (A5) ppm. Avenacins, triterpenoid saponins from oats, may be important determinants of disease-resistance and a source of pathogen-suppressive activity in soils. Analytical protocols developed to quantify avenacins were used to show intervarietal differences in production of these compounds, their location in the root zone, and their susceptibility to turnover.