1a. Objectives (from AD-416)
Develop reliable high throughput methods of phenotyping common scab resistance. Accelerate selection of breeding lines combining chip processing, late blight and scab resistance.
1b. Approach (from AD-416)
In cooperation with Sklarczyk Minitubers, Johannesburg, MI, a hydroponic tuberization system (nutrient film technology or NFT) has been set up at Michigan State. Initial experiments will be conducted to examine how nutrient solution pH, inoculum concentration and timing of inoculation influence scab lesion development on a set of four lines that differ in their scab reaction under field conditions. The validated NFT system will be further used to evaluate commonly grown varieties and breeding material, as well as for phenotyping scab tolerance in populations developed during other research projects. We will evaluate 117 crosses comprising about 500 selections segregating for common scab resistance, late blight resistance and chip-processing to select optimal lines with good agronomic traits that also combine these three characteristics for further advancement in our breeding program. In addition, 53 lines that may combine scab resistance, late blight resistance and chip-processing will be evaluated in replicated trials for agronomic performance in 2009 and also screened in replicated trials for late blight and scab resistance.
3. Progress Report
To devise quicker and more reproducible methods of screening for potato common scab resistance, a nutrient film technology (NFT) hydroponic mini-tuberization system is being used at Michigan State University. Methods are now optimized for production of healthy tubers, and for treatment with the scab-causing pathogen, Streptomyces scabies. Replicated trials on 12 (susceptible and resistant) potato breeding lines and cultivars that vary in their response to common scab in previously conducted field and greenhouse trials are now in progress. The NFT scab results will be compared to previous field and greenhouse trial results to validate the method. A fully validated NFT assay will reduce the need for years of field-testing when breeding for common scab resistance, and provide potato growers with new common-scab resistant varieties. Two critical agronomic characteristics were combined in tests for resistance to the diseases potato common scab and late blight. In 2010, a total of 297 lines were evaluated in three field locations for resistance to potato common scab resistance. Based upon the data collected, the level of common scab resistance has increased in the breeding program over 5 years, with nearly twice as many resistant lines resistant to common scab as susceptible in the most advanced potato lines. Of 104 newly-developed potato lines tested for late blight resistance in potato leaves, 33 were resistant or moderately resistant. Of the 160 advanced selections tested, 41 were resistant or moderately resistant to late blight. Late blight and common scab are the two most important potato diseases in the upper Midwestern United States, and disease-resistant varieties will improve potato health and productivity, while reducing use of agrochemical controls. These results contribute directly to the objectives of the parent project to enhance control of these diseases. Progress by Michigan State collaborators was monitored by regular telephone calls, exchange of e-mails, a visit to Michigan State, and receipt of preliminary written reports containing experimental results.