Integrated management strategies and pathogen detection in the potato-Streptomyces spp. pathosystem

The cultivated potato, Solanum tuberosum L., is the world's most important dicotyledonous food crop. It is surpassed only by wheat, rice, and corn as the world's fourth most important human food source. This research examined the potential use of environmentally friendly disease management tools in reducing the severity of an important bacterial disease, potato common scab, and examined the potential use of molecular methods for detection and quantification of the causal agents (Streptomyces spp.).; Controlled environment and field experiments were conducted to determine the effectiveness of cultivar resistance and soil moisture in reducing scab. Cultivar resistance appeared to be the most effective means of decreasing scab infections. When resistance was combined with irrigation at field capacity, disease reduction was slightly enhanced. Common scab reduction occurred for susceptible cultivars when soil moisture was maintained at field capacity; however, the control was not as effective as the reduction that occurred with the intermediately resistant and resistant cultivars.; The use of resistance activators for elicitation of systemic acquired resistance (SAR) in potato to common scab in field experiments produced variable results. While many elicitor treatments resulted in more scab free tubers one year, the following two years no significant differences were noted. Temperature and soil moisture may have led to the interannual variability. No increases in chitinase activity (a marker for SAR) in tuber tissue were detected, thus SAR was not induced.; PCR and real time PCR were used as pathogen detection and quantification methods, respectively. The nec1 gene (associated with pathogenicity in Streptomyces spp.) was used to screen isolates obtained from soil from potato fields in Michigan production counties. The pathogen was detected in each county. Slight differences in pathogen population between fields were detected by real time PCR.; These findings demonstrate that cultivar resistance is the primary method for managing common scab. Soil moisture application is also important, especially for susceptible cultivars. SAR may provide more scab-free tubers if combined with other management methods. As a stand-alone management tool, it did not decrease scab. Also, detection of pathogenic Streptomyces spp. was achieved by PCR. Real time PCR was reliable for quantification, but is less economic.