Date of Award

Spring 2014

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Botany and Plant Pathology

First Advisor

Teresa J. Hughes

Committee Member 1

Kiersten A. Wise

Committee Member 2

Katy Rainey

Abstract

The fungal pathogen, Macrophomina phaseolina, causes the disease charcoal rot (CR), which greatly impacts soybean production. Host resistance to CR is the primary means of managing this disease, yet resistance in commercial soybean cultivars in Maturity Groups (MG) I-III is currently unknown. Thirty (30) and sixty-seven (67) entries to the 2012 Wisconsin (MG I-II) and Indiana (MG II-III) Soybean Variety Trials, respectively, were evaluated for resistance to CR using a cut-stem assay. Disease was characterized as an area under the disease progress curve (AUDPC) based on lesion development and resistance assessed in relation to the resistant check (DT97-4290). In each experimental run, the cut-stem method consistently differentiated between the CR-resistant and susceptible (Pharaoh) checks. Likewise, disease development in each of the selected cultivars was comparable across all experiments based on experiment × cultivar interactions (WI: p=0.263, IN: p=0.185). The reaction of both the WI and IN cultivars to M. phaseolina ranged from susceptible to moderately resistant. Although no cultivar was immune to M. phaseolina, three MG I-II and 16 MG II-III cultivars performed similar to or better than DT97-4290 and had significantly lower AUDPC than Pharaoh. Results of this study indicate there are commercial cultivars available to manage CR in the upper Midwest.

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