Session 3, Abstract 17

UNDERSTANDING GENETIC DIVERSITY AND HOW EFFLUX PROTEINS CONTRIBUTE TO FUNGICIDE RESISTANCE IN ​COLLETOTRICHUM ACUTATUM ​COLLECTED FROM STRAWBERRIES GROWN IN CALIFORNIA

Austin L Coleman* and Jake R Erickson (Moytri RoyChowdhury), Idaho State University, Dept. of Biological Sciences, 650 Memorial Dr., Gale Life Science Building, Pocatello, ID 83209

Various fungicides were assessed for their ability to control strawberry anthracnose caused by the fungus Colletotrichum acutatum under laboratory conditions. A 99% mycelial growth inhibition was observed using Tilt (28µl). A 96% inhibition was observed using Quadris Top (65.5µl). A 76% inhibition was observed using Captan (450mg). A 57% inhibition was observed using Pristine (103.25mg). A 52% inhibition was observed using Bravo (112.5µl). A 36% inhibition was observed using Merivon (51.5µl). A 28% inhibition was observed using Topsin (72mg). An 11% inhibition was observed using Abound (72.75µl). A 9% overgrowth was observed using Regalia (450µl). A control plate was used to calculate the percent inhibition and overgrowth. Microscopy studies revealed significantly smaller conidia sizes when the fungus was grown in media with Captan, Quadris Top and Pristine. Conidia were not observed when the media contained Tilt. Sequence analysis of the pathogen grown on different fungicides revealed genetic diversity. A phylogenetic tree developed on sequencing information of an intergenic spacer region indicated pathogen grown on Tilt and Quadris Top to be resistant. To test the contribution of efflux proteins to resistance, we used confocal microscopy to study plasma membrane associated fluorescence. One of the transporter inhibitory compounds, 2-(4-ethoxy-phenyl)-chromen-4-one (15µM), completely eliminated plasma membrane-associated fluorescence in Quadris Top and Tilt. Abound and Regalia did not eliminate cytoplasm-associated fluorescence. Milbemycin oxime (64µM), another transporter inhibitor, showed a strong fungicidal effect, but did not exhibit significant inhibitory effects on plasma membrane-associated fluorescence.

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