Analysis Of Resistance Genes To Phytophthora Root Rot In Soybean Germplasm And Mapping Of Phytophthora Resistance Gene In Cultivar Soybean Wandou15

Soybean is one of major oil crops in the world. Phytophthora root and stem rot (PRR) of soybean caused by Phytophthora sojae Kaufm. & Gerd. is the most damaging disease of soybean, following soybean cyst nematode (SCN). In China, this disease has been heavily occurring in Heilongjiang and Fujian provinces. Soybean germplasm from China and USA were identified for their reactions to 13 pathotypes of P. sojae using the hypocotyl inoculation technique, and their genes or combinations of genes were postulated, and molecular detection was conducted in some soybean germplasm which have been postulated to carry alleles in Rps1 locus. In addition, a novel Rps gene designated RpsWD 15 in commercial cultivar Wandou15 was mapped. The main results were as follows:1. One hundred and fifty-six soybean accessions were identified for their reactions to 13 pathotypes of P. sojae using the hypocotyl inoculation technique in greenhouse. One hundred and twenty-five accessions were resistant to one or more pathotypes, and these resistance accessions elicited 90 different reaction types. Phytophthora resistance genes in the resistance accessions were postulated by comparisons of the reaction types of differential soybean cultivars or lines possessing known single Phytophthora resistance gene. Ten reaction types were consistent with the reaction types of a single gene or two-gene combinations. These accessions were postulated to carry Rps1a, Rps1b, Rps1d, Rps1k, Rps3a, Rps3b, Rps3c, Rps4, Rps5, Rps6, Rps7 or Rps8.2. Eighty-five soybean cultivars or lines from America were identified for their reactions to 13 pathotypes of P. sojae using the hypocotyl inoculation technique. It was found that 72 cultivars or lines were resistant to one or more P. sojae pathotypes. Comparisons of reaction types of differential soybean cultivars or lines and pedigree analysis allowed postulation of genes or combinations of Rps genes in 35 cultivars or lines. Of the 35 cultivars or lines, 14 carrying Rps1a, one carrying Rps1c and two carrying Rps1k, they could be used as resistance parents in soybean breeding programs.3. According to the results of gene postulation, 41 soybean accessions postulated to carry allele in Rps1 locus were detected using SSR markers closely linked with Rps1a, Rps1b, Rps1c, Rps1d, and Rps1k, respectively. It was found that L60-246(Clark63), L72-1138, L63-1612, L72-1140, L83-4387, Maple Arrow, Dawson, Wilkin, Hodgson 78, Vinton 81, Beeson, L81-4871, Century lx13, Hoyt, Dunbar, Delsoy4710, L72D-4045, L88-8739, L69-4428, Kato, Hack and Jindou15 carried Rps1a; L82-1858 carried Rps1c; Qihuang1, Wenfeng7, Shidadou1, Kexin4, Meng9793-1, Jindou 31, Ludou4, Maoyandou (ZDD18835), Xinliuqing and Yudou12 carried Rps1d; L81-4590, Sprite 87, Amcor 89, L87-0482, Hobbit87 and 7651-1 carried Rps1k.4. A Phytophthora resistance gene designated RpsWD15 in commercial cultivar Wandou15 was mapped. RpsWD15 is a novel Rps gene which was first found on molecular linkage group D2, and flanked by SSR markers Satt514 and Satt543 with genetic distances of 4.8 cM and 3.1 cM, respectively.