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United States Department of Agriculture

Agricultural Research Service

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Research Project: Discovery of Novel Nematode Resistance Genes and Development of Productive Soybeans with Multiple-Nematode Resistance

Location: Soybean/maize Germplasm, Pathology, and Genetics Research

Project Number: 5012-21000-026-22
Project Type: Reimbursable

Start Date: Oct 01, 2013
End Date: Sep 30, 2014

Objective:
Objective 1. Application of biotechnology to control the soybean cyst nematode: Genetic diversity and soybean genetic resources; Objective 2: Genetic evaluation and development of germplasm resistant to multi-nematodes in group III, IV, and V soybeans; and, Objective 3: Screen lines derived from crosses between soybean and G. tomentella and identify lines that have SCN resistance transferred from the G. tomentella parent.

Approach:
Our involvement in this project is solely in objective 3. We will continue to produce new G. tomentella-derived genetically stable lines from a variety of BC2 plants using our patented procedure with PI 441001 (G. tomentella) as either the male or female parent. The crossing and backcrossing will be done in the greenhouse until self-fertile plants are produced. Seeds from these self-fertile plants will be planted in the field and individual plants will be harvested and replanted until the resulting rows are uniform in appearance. These genetically stable, inbred lines will be harvested and tested for SCN resistance. Each year we will screen at least 1000 G. tomentella-derived lines. Initial tests will be unreplicated to maximize the number of lines that can be screened. The screening procedure that will be used is the standard published method of Niblack. Initial screening will be with HG type 2.5.7. to identify the resistance that is different from that in the soybean parent. Those lines with a female index less than 40 will be retested in replicated tests. Those lines with confirmed resistant to HG type 2.5.7. will be tested for resistance to HG type 1-7. Characterize G. tomentella-derived lines that are confirmed to be resistant to HG type 2.5.7. or HG type 1-7 and a similar sample of susceptible lines with DNA markers using a new procedure called genotyping by sequencing (GBS). With this system, marker genotyping is done using new, high-throughput sequencing technology that was developed for genome sequencing. GBS will cost about one quarter of the price of the most commonly used method for genotyping, and will provide many more markers. Using the sequence data, we will compare the differences between resistant and susceptible G. tomentella-derived lines. Since these are BC3 to BC5 lines, they are likely to be more than 95% identical. We will look for differences in the highly resistant lines that are not in Dwight which will tell us what was introgressed from G. tomentella and by comparing the highly susceptible lines with the highly resistance lines we can determine what was introgressed from G. tomentella but not contributing to SCN resistance. Because the expected genetic differences are small, we should be able to locate the regions contributing to SCN resistance. We will also cross the most highly resistant lines back to Dwight and begin developing QTL mapping populations that will allow us to more precisely locate the SCN resistance genes and identify markers that can be used to transfer this resistance into commercial varieties.

Last Modified: 10/21/2014
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