Announcement of Final Defense Plant Pathology M.S. Degree: River C Dean
July 24, 2025 9:00AM - 10:00AM
ZOOM Only
Contact Lauren for ZOOM info
Members of the Examining Committee and their Department:
- Mary Hausbeck – Plant, Soil and Microbial Sciences
- Roberto Lopez – Horticulture
- Jan Byrne – Plant, Soil, and Microbial Sciences
ABSTRACT
Downy mildew (DM) of impatiens (Impatiens walleriana), caused by the oomycete Plasmopara destructor (syn. P. obducens), leads to chlorosis, defoliation, and significant crop losses. Current management strategies include fungicides and genetic resistance. To limit DM and enhance plant quality, we conducted two separate experiments. In the first, Accent Premium White’ impatiens seeds were sown in a greenhouse maintained at 23 °C. A 9-hour short-day (SD) photoperiod was created using blackout curtains over individual greenhouse benches. Each bench was randomly assigned to one of eight day-extension photoperiod treatments: a 9-h SD (control) or a 9-h truncated SD extended to 16-h with low-intensity LED fixtures that provided 20 µmol·m–2·s–1 of blue (405 nm), blue (445 nm), green (525 nm), red (660 nm), far-red (730 nm), or white (18:38:41:3 blue:green:red:far-red) light for 7 hours, or a 9-h truncated SD extended by 6-hour intermittent ultraviolet-A (385 nm) radiation. Post-sowing (70 days), impatiens were inoculated with a P. destructor sporangial suspension. Ten days post-inoculation, disease incidence (proportion of diseased leaves) in the control was 43%, whereas the other treatments ranged from 14% to 54%. We also evaluated the efficacy of seven biorational products to limit DM disease on impatiens when compared with the industry-standard systemic fungicide containing oxathiapiprolin. The biorational products containing Bacillus amyloliquefaciens strain F727, phosphonates, or potassium bicarbonate demonstrated the greatest reduction in disease incidence and were statistically similar to the industry standard fungicide with the exception of potassium bicarbonate. These results provide insight into the potential for an integrated disease management program to reduce DM of impatiens by manipulating the photoperiod using selected light qualities and the application of plant protection products that are environmentally sustainable.
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