Helminthosporium solani: Biology, Occurrence, and Control

Potatoes are one of the top five organic vegetables purchased for home consumption in the United States. Many biotic and abiotic factors limit organic potato production and to meet the increasing consumer demand, especially from the fresh market, there is a need to produce good quality blemish-free potatoes. This research shows that silver scurf(caused by Helminthosporium solani ) and black dot (caused by Colletotrichum coccodes) are two prevalent diseases in organic potato production in Wisconsin, with high incidences across locations and cultivars. Seventy-five percent and 94% of asymptomatic tubers assessed were positive for H. solani and C. coccodes respectively. Because no cultivar has yet been identified that is completely resistant to silver scurf, we performed minituber inoculation assays and identified a diploid interspecific hybrid C287 that consistently supported little sporulation of H. solani, suggesting it has partial resistance to silver scurf. Although important, H. solani is an understudied pathogen with poor genomic information, and herein we report the draft genome of the fungus. The estimated genome size of H. solani is ~ 35 megabases. In silico genomic analysis suggests that the fungus possesses a large suite of genes encoding putative cell wall degrading enzymes.;We also explored alternate methods to control fungal pathogens of potato. We performed in vitro tests with tobacco phylloplanins (Nt-phylloplanins) using an inexpensive microfluidic approach to test for its inhibitory activity against plant and human fungal pathogens. Spores of Colletotrichum coccodes and Aspergillus fumigatus treated with Nt-phylloplanins did not germinate at the concentrations tested at 48 and 30 hours post treatment respectively. Inhibition of spore germination of the human pathogen A. fumigatus by Nt-phylloplanins also reveals a new venue for medicinal antifungal drug discovery that has not been explored previously.