Performing Department
(N/A)
Non Technical Summary
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.
Animal Health Component
0%
Research Effort Categories
Basic
10%
Applied
40%
Developmental
50%
Goals / Objectives
Our overall goal of this proposal is to make cucumber production more sustainable in the context of an evolving major challenge, the oomycete pathogen, cucurbit downy mildew (CDM). Improved downy mildew resistant cucumbers will provide growers with a cucumber crop that is more economical to grow without the expense of fungicides, or for gardeners and organic growers, the total loss of an unprotected crop. Cultivation of diverse resistance sources should further increase the longevity of crop resistance and provide alternatives to cultivars already in production should the pathogen evolve resistance to the narrow set of genetics currently in use. Food security and consumers will benefit from having better access to locally or US grown cucumbers. After substantial investment, and good reception of preceding cultivars, this proposal seeks to efficiently deliver to the marketplace improved, needed cultivars that were developed with the request and guidance from stakeholders. This will be accomplished through a set of objectives that span evaluation, seed production, and marketing.Objective 1 will focus on the evaluation of this new generation of cucurbit downy mildew resistant cucumbers through replicated research station trials, pilot production on grower farms, and genomic analysis to characterize the disease resistance genetics.Objective 2 will create seed resources to support and accelerate adoption by seed companies and future breeding efforts. We will create abundant, healthy foundation seed stocks for company seed production, efforts supporting hybrid seed production, and we will deposit a stock of a rare source of resistance in the National Plant Germplasm System.Objective 3 will support adoption directly by promotion to seed companies, securing PVPs, produce presence in a trend setting urban market and promotion through the Culinary Breeding Network.
Project Methods
Variety trials will be performed through replicated trials conducted on university research stations in a controlled setting. Standard production practices will be used for both conventional and organic production. Border rows of susceptible will provide intense and uniform disease pressure. Disease severity will be determined through observations of foliar symptoms and calculation of relative AUDPC. Cucumber yield and earliness will be determined through fruit harvests. Two years of data collected in New York (NY) and South Carolina (SC) will be statistically analyzed. Production scale on-farm trials will be subsequently conducted that will rely on anecdotal reactions from growers on relative preference of production of these crops at scale and reactions of their customers. The nature of the resistance in these lines will be explored through genomic analysis. Selective sweeps will be sought though computing FST across the genome of current and remnant seed across generations of breeding for CDMR. QTL-Seq will be complement FST in a newly generated population created by crossing a resistant breeding line to a susceptible cucumber, evaluating resistance in a segregating population. The resulting extremes of the population will be pooled for genome resequencing and a delta-SNP index will be calculated to identify some of the key QTL for resistance.For seed production, cucumber plots will be grown in spatial isolation or in pollination cages with honeybee nucs. Inspections performed by NYSIP during the plant growth phase will be helpful for phytosanitary clearance to allow seed companies to ship seed to international seed production nurseries. Fruit will be harvested at maturity and processed in a Millett wet vegetable seed extractor, fermented and cleaned, dried, separated by density in an air column and put into climate controlled seed storage. Genetic hybrid pairs will be explored through the use of a commonly available gynoecious cucumber inbred, Gy-14. Relative performance will be determined in our trials and relative flowing times for synchronizing male and female flower production for hybrids and seed yield will be observed the season before.We will determine ethrel response in the inbred line used as a female to determine best concentrations in these lines for efficient emasculation, collect production data and produce these for trials.Promotion will be conducted through Cornell's Vegetable Breeding Institute field days and acquiring PVPs on exceptional cultivars. Harvest will be featured in at least one prominent urban farmers market. The Culinary Breeding Network will promote these cucumbers through consumer engagement at public outreach events, the Variety Showcase, and exploration boxes to chefs and foodies. Broad communication will be supported through a social media campaign and press releases to the appropriate media.