WSU CAHNRS

College of Agricultural, Human, and Natural Resource Sciences

Department of Plant Pathology

PhD student’s successful thesis defense

Congratulations to Ms. Emily Gatch, PhD student with Dr. Lindsey du Toit, for successfully defending her PhD thesis.

Emily’s PhD supervisory committee included, Drs. Lindsey du Toit (chair), Thomas Gordon (UC Davis), Mark Mazzola, Bill Pan and Tim Paulitz. Her dissertation research dealt with management of Fusarium wilt in spinach seed crops.

Gatch Committee

5’ to 3’ end: Tom Gordon, Mark Mazzola, Tim Paulitz, Emily Gatch, Lindsey du Toit, and Bill Pan

The maritime Pacific Northwest is the only region of the USA suitable for production of spinach seed, a cool-season, daylength-sensitive crop.  However, the acidic soils of this region are highly conducive to spinach Fusarium wilt. Rotations of 10 to 15 years between spinach seed crops are necessary to reduce the risk of losses to this disease. Raising soil pH with limestone partially suppresses spinach Fusarium wilt, but the suppressive effect is transitory, and the disease still limits seed crop acreage in the region.

Emily conducted experiments to assess the potential for annual applications of limestone for three years prior to a spinach seed crop to improve Fusarium wilt suppression compared to the level of suppression from a single limestone amendment, develop a soil-based greenhouse bioassay to characterize the spinach Fusarium wilt risk of soil samples submitted from stakeholders’ fields, and explore the mechanism(s) of limestone-mediated Fusarium wilt suppression.

Emily found out that annual applications of limestone for each of three years prior to a spinach seed crop were superior to a single limestone application for suppressing Fusarium wilt and increasing seed yield. She developed and validated a soil bioassay to assess Fusarium wilt risk. Through in vitro experiments, Emily demonstrated that deficiencies of iron, manganese, and zinc can reduce growth and sporulation of the pathogen. Furthermore, greenhouse experiments in naturally-infested field soil indicated that reduction in availability of these micronutrients in limestone-amended soils reduced Fusarium wilt inoculum potential.

Emily’s research demonstrated relationships among soil properties and spinach Fusarium wilt development, increased the capacity for and profitability of USA spinach seed production, and will guide future research on soil-based management of this disease.

Emily obtained her B.A. in Biology from Harvard University, an M.S. in Plant Pathology from Iowa State University.  After M.S., she worked as a research associate for the University of Tennessee in horticultural crops for three years, followed by three years at Seeds of Change, an organic vegetable seed company before joining WSU Plant Pathology for her PhD.

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