ARS | Publication request: Re-collection of Helianthus argophyllus, source of the PlArg gene from downy mildew resistance, surviving for 25 years on Daytona Beach, Florida

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 7, 2007
Publication Date: February 7, 2007
Repository URL: http://www.sunflowernsa.com/research/research-workshop/documents/Seiler_etal_Daytona_07.pdf
Citation: Seiler, G.J., Gulya Jr, T.J., Marek, L.F. 2007. Re-collection of Helianthus argophyllus, source of the PlArg gene from downy mildew resistance, surviving for 25 years on Daytona Beach, Florida. 29th Sunflower Research Workshop, January 10-11, 2007, Fargo, ND. Available: http://www.sunflowernsa.com/research/research-workshop/documents/Seiler_etal_Daytona_07.pdf

Interpretive Summary: Wild sunflower species have been a valuable source of resistance genes for many of the common pathogens of cultivated sunflower. One example is downy mildew which occurs in most countries where sunflower is grown, with the apparent exception of Australia. The pathogen is unique in that it infects the seedling roots to initiate a systemic, often terminal disease, while airborne spores cause only local lesions. Until recently, fungicide seed treatments Apron was used to control downy mildew, but the fungus has developed resistance to the chemicals. One species of wild sunflower, silver leaf sunflower, H. argophyllus, is a source of a dominant gene for resistance to all known races of downy mildew. The source of this resistance was collected from a population on the popular Daytona Beach in Florida. Since it had been over 25 years since last visiting the original site on the very popular Daytona Beach in Florida, an exploration in September, 2006 was undertaken to revisit the site to determine if this population had survived and if found, collect seed for the wild sunflower germplasm collection. Surprisingly, a population of the silver leaf sunflower still existed at the Daytona Beach site. The population has expanded its distribution into an abandoned lot next to oceanfront homes. About 50 plants were scattered throughout the immediate area. There were no plants where the original three plants had been located in 1980, which was near the access road to the beach. The beach is open to vehicle traffic, but the sunflower was near the edge of the upper part of the beach near the homes. Considerable urbanization had taken place in the area, but for some reason the two oceanfront homes have survived and still provide a habitat for the wild sunflower to survive. Predictions as to what will happen to this population in the next 25 years can only be speculation. Nevertheless, sufficient seed has been collected from the population for the USDA-ARS sunflower germplasm collection to preserve it for future use.

Technical Abstract: The genus Helianthus, besides constituting the basic genetic stock from which cultivated sunflower originated, continues to contribute unique characteristics for cultivated sunflower improvement. Genetic diversity of the wild species has allowed the crop to become and remain economically viable by contributing genes for resistance (tolerance) to pests and environmental stresses. However, there is a continued need to collect, maintain, and evaluate wild Helianthus germplasm for future utilization and enhancement of cultivated sunflower. The encroachment of humans into the habitats of some wild species is an urgent concern. A population of Helianthus argophyllus (ARG-1575, PI 468651) collected on Daytona Beach, Volusia County, Florida, in October, 1980. This population contained genes that were used to develop an interspecific germplasm ARG-1575-2 (PI 539913), which was resistant to all known races of downy mildew. Since only three plants were originally found, it appeared that this population was in imminent danger of being eliminated. Surprisingly, when this local was revisited in September, 2006, 50 plants were found scattered in an abandoned beachfront lot near the original collection site. Urbanization of this area is continuing, so it is hard to predict how long this population will survive. An abundance of seeds were collected and deposited in the sunflower germplasm collection at the USDA-ARS-NCRPIS, Ames, IA.