Submitted to: Crop Science
Publication Type: Germplasm release
Publication Acceptance Date: 9/27/2006
Publication Date: 2/1/2007
Citation: Mengistu, A., Kilen, T.C., Donald, P.A. 2007. Registration of D95-5048 Soybean Germplasm Line Resistant to Phytophthora Rot and Soybean Cyst Nematode Races 3 and 14. Crop Science. 47:452-453. Interpretive Summary: Phytophthora rot, caused by the fungus (mold) Phytophthora sojae, and soybean cyst nematode (a microscopic-sized worm) Heterodera glycines, are serious yield-limiting diseases of soybean. In order to mitigate yield losses caused by these two diseases, it was essential to develop germplasm having high yield and multiple-pest resistance. Because Bedford has a moderate level of resistance to race 14 of soybean cyst nematode and is highly resistant to race 3, it was used as one of the parents in the breeding experiment. As a result, soybean germplasm line D95-5048 was developed and released in May 2005. This line has value because of its resistance to phytophthora rot and races 3 and 14 of soybean cyst nematode. It also has value to the private and public soybean breeders because it will expand the set of previous releases of phytophthora rot resistant lines. This unique gene for phytophthora rot resistance along with the previous releases makes it useful as a diagnostic tool to identify races of the fungus causing phytophthora rot.
Technical Abstract: Soybean germplasm line D95-5048 was released in May 2005. The objective was to provide private and public soybean breeders with a parent to develop high yielding, multiple pest resistant cultivars. Phytophthora rot (PR) and soybean cyst nematode (SCN) continue to be serious yield-limiting diseases of soybean. D95-5048 is a product of a backcross to transfer the allele Rps1-b into a Bedford background. The Rps1-b allele confers resistance to races, 3-9, 13, 15, 18, 21 and 22 of PR. D95-5048 has value to the research community because it will expand the set of previous releases of PR-resistant lines which are near-isogenic to the cultivar Bedford. It can also be used in concert to pyramid genes for phytophthora resistance. The reaction of 12 F3 plants was used to identify lines uniformly resistant to PR. F2:3 lines uniformly resistant to PR were selected as pollen parents between each of the five crossing cycles. Seedlings were inoculated in a greenhouse during the years 2000 through 2002 by the hypocotyl puncture method using race 1 of the pathogen. After the fourth backcross to Bedford, an F3 line uniformly resistant to race 1 was increased for two generations, and 100 F5 plants were again inoculated with race 1 to verify the reaction of the F3. After the fourth backcross to Bedford, an F3 line uniformly resistant to race 1 was increased for two generations, and 100 F5 plants were again inoculated with race 1 to verify the reaction of the F3. During these 4 years, visual selection was made to complete the recovery of the morphological type of the recurrent parent. One hundred F5 plants were inoculated with race 1 to verify the reaction of the F3. Approximately 100 plants were also inoculated with race 1 at the F8 generation. D95-5048 was evaluated in F8 generation for reaction to races 3 and 14 of the SCN at Jackson, TN. In replicated yield tests on clay soil at Stoneville, MS in 1999 through 2002, yields of D95-5048 and Bedford were 3756 kg ha-1 vs 3749 kg ha-1, 1566 kg ha-1 vs 1263 kg ha-1, 1646 kg ha-1 vs 1001 kg ha-1, and 3548 kg ha-1 vs 3265 kg ha-1respectively. The 4-year means were 2627 kg ha-1 for D95-5048 and 2318 kg ha-1 for Bedford. The differences in yield in the four years were significant at the P less than 0.01 level. A breeding line [D55-1492, from (Roanoke x Rose Non-pop) x (S100 x CNS)] grown in the same environment, but very susceptible to phytophthora rot, showed symptoms of the disease all 4 years while Bedford and D95-5048 showed none.