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United States Department of Agriculture

Agricultural Research Service

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Location: Plant Genetic Resources Research

2011 Annual Report

1a. Objectives (from AD-416)
1. Develop and release improved apple rootstocks. 2. Develop and apply genomic and bioinformatic tools to marker-assisted selection of apple rootstocks.

1b. Approach (from AD-416)
Develop and release improved apple rootstocks. Perform all breeding and evaluation stages involved in the 15-25 year process of developing new rootstocks with the assistance of recently developed breeding tools, such as marker-assisted selection. Develop improved propagation methods that speed the distribution of selected material to customers through established networks of cooperating nurseries. Exogenous treatments of layering propagation stool beds will increase adventitious root formation and quality of nursery liners. Incorporate innovative concepts of orchard establishment and management including mechanization. Existing experimental rootstocks in the breeding pipeline possess adaptations for novel orchard concepts and mechanization. Develop and apply genomic and bioinformatic tools to marker-assisted selection of apple rootstocks. Develop algorithms to assist with identifying specific markers for priority horticultural traits from the large body of expressed sequence tags (EST) and genomic sequence data now available.

3. Progress Report
Significant advancements were made in all the objectives of project 1910-21000-023-00D relevant to National Program 301 “Genetic Improvement” component and National Program 305 Component 1 “Integrated Sustainable Crop Production Systems”. The project is working on increasing plant material for advanced testing of CG.3001, a new disease resistant rootstock that is showing good potential for release to the industry in the near future. This rootstock maintains the standards of dwarfing, high productivity, fire blight and crown rot resistance, and immunity to wooly apple aphids that have been known to characterize Geneva rootstocks. A major effort was placed on the development of DNA markers that are linked to the most important selection traits for apple rootstocks. The effort was aimed at refining the type of markers that were to be used for Marker Assisted Breeding for dwarfing, precocity, wooly apple aphid resistance, and fire blight resistance. We used an approach that combined the analysis of the genomic sequence of G.41 (a dwarfing , precocious, wooly apple aphid immune and fire blight immune rootstock) and the analysis of the expression of candidate genes to discover specific mutations in the regions affecting those traits that could be used to design new more efficient markers. The application of these new markers will allow the reduction of costly field plots for the evaluation of new generations of apple rootstocks. The project suffered another major setback due to improper application of herbicides on propagation material. This was a similar but more drastic incident than the one reported for FY09. Several new experimental rootstocks were killed and lost after many years of testing and selection. Furthermore the propagation beds that would have been used as the basis for the incorporation of new types of orchard production systems were decimated. We are in the process of assessing long term damage to the project and determining viable alternatives to the research that was destroyed. It is likely that this setback will affect accomplishment of milestones related to propagation research. Fortunately, most of the elite material is also kept in a secondary test location in Washington State and will be used to recover some of the lost genotypes in Geneva. Despite these setbacks there was considerable progress in the breeding program with new evaluation trees planted, the measurement of tree size and productivity, the measurement of tolerance to diseases such as fire blight, the making new experimental trees in the nursery, the making new crosses, the harvesting and grading rootstock liners and the identification of a set of new elite testing lines took place during the course of the year. We continued a major effort into diagnostic DNA fingerprinting of apple rootstocks for proper identification of misidentified rootstocks and avoidance of potential downstream planting and propagation problems. This effort supports apple rootstock nurseries that propagate Geneva rootstocks.

4. Accomplishments

Last Modified: 10/20/2017
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