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Fungicide Sensitivity and Population Structure of Sclerotinia Sclerotiorum from Soybean in the North Central United States and Dry Bean in Mexico
Fungicides are integral to reduce yield loss from Sclerotinia sclerotiorum on dry bean and soybean, which are the focus of this dissertation. Chapter 2 identified factors that may increase the risk of fungicide resistance in S. Sclerotiorum, such as the rise of low cost generic fungicides and application of strobilurins for plant health; such issues raise important questions about alternatives to synthetic fungicides like mycoparasites, mycoviruses, and RNA silencing. Research in Chapter 3 was conducted to elucidate the relationship between fungicide use and fungicide sensitivity of S. sclerotiorum from different hosts and regions. Fungicide sensitivity of 512 S. sclerotiorum from the USA, Brazil, and Mexico was determined using a discriminatory concentration for common fungicides used in soybean and baseline sensitivity of S. sclerotiorum was established. Results showed two S. sclerotiorum isolates from Mexico had mutations known to confer resistance in the SdhB (qualitative) and SdhC (quantitative) genes, however, no strong resistance was found. Then in Chapter 4, to test if there are different populations among regions with different climates; a hierarchical sampling of 178 S. sclerotiorum from dry bean and soybean from different regions were genotyped using AmpSeq (next-generation sequencing of multiple target loci). Preliminary results identified 16 S. sclerotiorum samples possessed a target-site mutation in the SdhB gene, which represented up to 33% of samples with sequence data. This proof-of-concept showed the AmpSeq technique is a promising new approach for broad-scale characterization of S. sclerotiorum. Collectively, the knowledge generated here improves our short- and long-term management of the disease.
Nieto-Lopez, Edgar H, "Fungicide Sensitivity and Population Structure of Sclerotinia Sclerotiorum from Soybean in the North Central United States and Dry Bean in Mexico" (2021). ETD collection for University of Nebraska-Lincoln. AAI28865685.