Location: Vegetable Crops Research2011 Annual Report
1a. Objectives (from AD-416)
Objective 1. Initiate an integrated cranberry genetics and genetic improvement plan to develop enhanced germplasm and superior new cultivars of cranberry adapted for a short growing season climate with superior productivity, increased disease resistance, enhanced nutritional characteristics, improved environmental adaptation (especially cold tolerance), and more uniform ripening with excellent berry color. Evaluate field performance and quality under current commercial conditions as well as under enhanced production systems utilizing new IPM and water management technologies. Objective 2. Initiate an innovative and integrated research program to characterize current insect pest damage of the cranberry crops, develop efficacious and economical insect Integrated Pest Management (IPM) strategies for cranberry production systems, and respond to emerging insect pests. Evaluate field performance under current commercial conditions as well as under enhanced production systems utilizing new cranberry varieties and new water management technologies.
1b. Approach (from AD-416)
For Objective 1, novel phenotypic variation will be identified, genetically characterized, mapped on the cranberry genome, and key genes incorporated into breeding stocks that are well-adapted for commercial growers. DNA polymorphisms and molecular tools will be developed to improve the efficiency of cranberry breeding. Methods for accurately phenotyping traits of importance will be developed and promising genetic selections will be tracked in commercial production systems that include up-to-date IPM and water management technologies. For Objective 2, novel pest management strategies will be developed and evaluated including, but not limited to, biological controls, host pest resistances, reduced risk chemicals, and cultural practices. Pest biologies will be studied to develop models for making optimal control decisions directly applicable to commercial production systems. Environmental impact of climate change, emerging water management issues and their application to new cranberry cultivars will be incorporated into reduced-risk pest management strategies developed and evaluated in commercial production systems.
3. Progress Report
Objective 1: As a first step in cultivar development, genomic tools are being created that will later help identify the physical chromosomal location of genes that explain differences among unique cranberry plants. Large numbers of molecular markers have been identified using next generation sequencing. Such markers were bioinformatically, analyzed to generate a marker set with the best genetic characteristics to provide information about cultivated and wild cranberry germplasm. The ultimate goal of the project is to generate thousands of molecular markers useful for genetic studies. These markers will be immediately useful for the genetic characterization of cultivated and natural plant germplasm, gene mapping of chromosomes, and the discovery of best parental combinations in cranberry for controlled crosses prioritization. Cultivated and wild cranberry genotypes are being collected around the U.S. We are evaluating the genetic diversity of the entire cranberry collection preserved at the USDA-ARS National Clonal Germplasm Repository (NCGR). An initial genetic survey of cultivated and wild cranberries is being conducted in Wisconsin. Objective 2: Flooding of cranberry beds as an insect control tactic was undertaken during the spring of 2011. Flood-water characteristics, plant responses, and insect population densities were evaluated in a large-scale field trial in central Wisconsin. Flooded beds were paired with unflooded beds at each of eleven commercial marshes, which included 46 beds across three cranberry varieties. In parallel, greenhouse trials were conducted to assay the submergence tolerance of the three cranberry varieties. From the flooding trials, our evidence suggests that when dissolved oxygen levels in flood-waters remain above 70% saturation, the three main cranberry varieties grown in WI can be flooded with no damage to plant tissues. Insect densities continue to be monitored in the field, and to-date, it appears that insect densities were reduced in the flooded beds. Unflooded beds required an insecticide spray to lower pest densities down to those of flooded beds, suggesting that flooding may effectively reduce the number insecticide sprays in Wisconsin’s cranberry marshes. Reducing insecticide loads is particularly important because cranberry marshes exist within a broader wetland ecosystem, and there is much movement of surface waters from on-farm acreage to off-farm landscapes. A Food Web Workgroup has been assembled to investigate the trophic structure of terrestrial ecosystems. The group will be employing a new method of empirically measuring the trophic level (position within a food chain) of organisms, which will open the door for many studies of community structure in Wisconsin landscapes. For the cranberry industry, we will be able to determine, for the first time ever, whether predator populations are primarily beneficial, neutral, or pests. Beneficial insect populations form the basis of biological control, which is a pillar of IPM.
1. Genetic and genomic tools development. Little genetic information is available to help improve the breeding efficiency of cranberry cultivars. Thus, the genetic code of cranberry was studied using next-generation sequencing approaches and a total of 107,244 molecular markers were identified. An initial set of 96 DNA markers were developed to study cranberry. In the future, genetic and genomic tools in cranberry will lead to innovative plant breeding systems to speed the breeding of unique cranberry cultivars to meet the current and future challenges of an important crop for American industry.
2. Cranberry diversity assessment. The genetic relationship and purity among and within cranberry cultivars is largely unknown. Thus, the genetic diversity of 25 cranberry plants from National Clonal Germplasm Repository (NCGR) was studied using molecular markers. A total of 48 useful molecular markers in the 25 cranberry plants were discovered that provide useful information about kinship relationships and cultivar purity. Additionally, an initial large scale genetic evaluation using 288 diverse cranberry plants and 12 genetic markers was accomplished, and this will provide fundamental genetic information for breeding and genetic studies leading to a more suitable and profitable cranberry crop.
3. Submergence tolerance of cranberry plants. Insect control is a serious problem for the cranberry industry, but few non-chemically based methods exist to reliably resolve this perennial concern. Flooding of cranberry beds has been used to control arthropod pests for many years, yet there is still no consensus as to appropriate flood-water characteristics, flooding duration, or the effects of prolonged submergence on the cranberry plant. To attend to this gap in our knowledge and thereby develop an optimal flooding strategy, large-scale flooding trials were conducted, involving 46 beds (23 pairs of flooded and unflooded beds) across 11 commercial marshes in the major cranberry production region of Wisconsin. This work has shown that when dissolved oxygen levels are high in flood-waters (saturation above 70%), the cranberry crop (three different cranberry varieties) can be flooded for 30-40 hours with little or no damage to plant tissues. Insect densities continue to be monitored in the field, and to-date, the data strongly suggest that flooding effectively reduced pest densities, such that flooded beds were equivalent to (or lower than) their corresponding non-flooded, chemically treated beds. This is the first evidence that flooding may effectively reduce the number of insecticide sprays in Wisconsin’s cranberry marshes. Insecticide residues are of particular concern to the industry and the public, given that most commercial marshes are within or adjacent to sensitive wetland habitats.