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Soybean Germplasm From Anhui To Zhejiang
For BSR Resistance To Yield Improvement

Randall Nelson
Research Geneticist and Professor of Plant Genetics
USDA-ARS and Department of Crop Sciences
(217) 244-4346; rlnelson@illinois.edu
Randall Nelson

The soybean originated in China. Illinois varieties are descended from Chinese varieties that were introduced into the United States before 1930. Only eight of these varieties contribute 75 percent of the genes in our current varieties. This narrow genetic base could be a limitation to future progress to increase yield.

Other varieties have been used as sources of disease resistance. The contribution of these varieties has been critical to prevent losses due to disease but does not increase the overall level of productivity. In recent years, we have seen the development of new diseases, such as sudden death syndrome and white mold, and changes in the pathogen populations of diseases such as Phytophthora rot and soybean cyst nematode. Finding new genes for resistance to these diseases is critically important for soybean production in Illinois. Because the soybean originated in China, the maximum genetic diversity for any trait is most likely to occur in varieties that originate from China. Most of the genes for disease resistance in current commercial varieties came from China.

Figure 1

Figure 1. Soybean varieties from different regions of China
introduced into the United States.

Between 1949 and 1974, soybean became a major crop in Illinois, but we had no opportunity to exchange soybean germplasm with China. In 1992, the Illinois Soybean Program Operating Board, the Illinois Agricultural Experiment Station, and USDA-Agricultural Research Service formed a group that established a germplasm exchange project with the Chinese Ministry of Agriculture. This collaboration increased the number of Chinese varieties in the USDA Soybean Germplasm Collection at the University of Illinois from 2,900 to nearly 6,100. The new additions represent all of the soybean growing regions of China. Prior to 1992, nearly 80 percent of the Chinese varieties in our collection came from only three provinces in northeast China, and many provinces were not represented.

Extensive research supported by the United Soybean Board has demonstrated the genetic uniqueness of these Chinese varieties and the value of this diversity. The highest level of resistance known to sudden death syndrome was identified, as were new sources of resistance to soybean cyst nematode, root knot nematode, frogeye leafspot, white mold, brown stem rot, Phytophthora rot, and leaf-feeding insects. Preliminary data indicate that tolerance to drought may exist in varieties from areas adjacent to the Gobi Desert. Genetic research is continuing, and these new genes are being incorporated into commercial varieties.

Exotic germplasm also has the potential to improve the yield of Illinois varieties. Over the past six years, we have released 14 experimental lines that are being used by universities and private companies to develop new varieties. The pedigrees of these experimental lines include 21 exotic parents. By making comparisons at the DNA level, we can estimate the degree of relatedness among lines for which no pedigree information is available. Based on DNA similarities, the major ancestral lines of U.S. varieties have been placed into six genetic groups. Our exotic parents represent nine genetic groups that are genetically distinct from the groups containing the major U.S. ancestral lines.

Our most recent releases were evaluated at nine locations in regional tests in 2001. One line derived from 25 percent exotic germplasm exceeded the yield of the best commercial variety by nearly 12 percent and was the highest-yielding entry in the test. Another released experimental line was derived solely from six exotic lines representing four different genetic groups and equaled the yield of the best commercial variety in the test.

The application of new technology will continue to facilitate the utilization of exotic germplasm to enhanced disease resistance, increased yield, and improved seed composition.

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