BRINGING THIRD GENERATION DOWNY MILDEW RESISTANT CUCUMBERS TO MARKET

Cucurbit downy mildew (CDM) is one of the most devastating and widespread diseases of cultivated cucurbits in the United States and worldwide. Symptoms of downy mildew occur on foliage and are promoted by warm days and cool humid nights which are typical of many cucumber-producing regions in the eastern United States. The pathogen is spread on wind currents from areas where the pathogen overwinters and can travel for hundreds of kilometers and can result in whole plant death in a matter of weeks. For decades, downy mildew on cucumbers in the United States was effectively managed with resistant cultivars and was not a major production concern. However, the resistance of commercial cultivars in the United States was defeated in 2004 when a new strain of P. cubensis emerged in North Carolina and spread northward to surrounding states). In some production environments, growers experienced 95% to 100% yield loss, leading to substantial economic losses, including $16 million in North Carolina alone during the 2004 epidemic. In many northern areas, organic cucumber growers and those harvesting in the late season have responded to the disease by ceasing production entirely after downy mildew moves into their local areas. To complement efforts by others that tended to reply on a single new source of resistance, we sought to help future-proof our efforts to breed resistant cucumber by breeding cultivars that combined other alternative sources of resistance. This successfully developed DMR 264 and DMR401, the most downy mildew resistant cucumber cultivars to date. However, while this cultivar outperforms other cultivars under disease pressure, its horticultural and agronomic characteristics could still be improved and we have done so. These new cucumbers combine excellent resistance with yields that far surpass DMR401.This project will help us effectively deliver the efforts of our breeding efforts to growers and consumers. The yield and resistance of these cucumbers will be quantitatively assessed by variety trials in conventional and organic conditions and research stations and on grower farms. The generation of foundation seed and seed production information for pureline and hybrid cultivars is often a gap in many public breeding programs and addressing this will facilitate the adoption of these cultivars by seed companies. Marketing will be done through partnerships with the Vegetable Breeding Institute and Culinary Breeding Network to seed companies and growers, consumers and the culinary community. While we release cultivars nonexclusively, it is done so with a license from Cornell University with a royalty returned to directly support continued vegetable cultivar development and graduate student training. Seed of the unique source of resistance used by our breeding program will be multiplied and shared with the USDA's National Plant Germplasm System to be available to other researchers.