Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2014
Publication Date: 2/27/2014
Publication URL: http://handle.nal.usda.gov/10113/58996
Citation: Zhang, A., Hao, J., Yuan, J., Song, Q., Hyten, D., Cregan, P.B., Zhang, G., Gu, C., Li, M., Wang, D. 2014. Phytophthora root rot resistance in soybean E00003. Crop Science. 54(2):492-499. Interpretive Summary: Phytophthora root rot (PRR) has long been a serious disease impacting soybean production in the U.S.A. The use of PRR resistant soybean varieties has and continues to be the best approach to combat this disease. The use of genetic markers to identify breeding lines that carry resistance to PRR avoids the need to conduct laborious greenhouse screening tests to identify lines that are resistant to PRR. Thus, the objective of this research was to determine the genetic control of resistance to PRR in the highly resistant soybean line E00003 and then to find genetic markers that can be used to identify breeding lines that carry the resistance gene(s) in E00003. A total of 240 breeding lines derived from a cross of E00003 with a PRR susceptible soybean were analyzed for resistance to PRR using three different races of PRR. The breeding lines were also analyzed with simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) DNA markers in order to find DNA markers associated with the gene(s) controlling resistance to PRR. PRR resistance was determined to be controlled by one major gene and two SSR and three SNP DNA markers were found to be closely associated with the gene. The resistance gene was determined to be the Rps1k gene. The SSR and SNP markers in close proximity to the gene can be used by soybean breeders to identify soybean breeding lines that carry the Rps1k resistance gene.
Technical Abstract: Phytophthora root rot (PRR), caused by the oomycete Phytophthora sojae, is a devastating disease in soybean production. Using resistant cultivars has been suggested as the best solution for disease management. Michigan elite soybean E00003 is resistant to P. sojae and has been used as a PRR resistance source in breeding of new cultivars. However, the genetic control of PRR resistance in E00003 is unknown. To facilitate marker-assisted selection (MAS), the PRR resistance loci in E00003 and their map locations need to be determined. In this study, a genetic mapping approach was employed to identify major PRR resistant loci in E00003. The mapping population consists of 240 F4-derived lines developed by crossing E00003 with the P. sojae susceptible line PI 567543C. In 2009 and 2010, the mapping population was evaluated in the greenhouse for PRR resistance against P. sojae races 1, 4, and 7, using a modified rice grain inoculation method. The population was genotyped with simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers. The heritability of resistance in the population ranged from 83% to 94%. A major locus, contributing 50% to 76% of the phenotypic variation, was mapped within a 3 cM interval in the Rps1 region. Based on the specific responses to the tested races, this locus was determined to be Rps1k. To pinpoint the functional gene, the interval was further saturated with more BARCSOY SSRs and SNPs with TaqMan® assays. Two SSRs and three SNPs were found located within the predicted functional gene; these are highly associated with PRR resistance in the mapping population. These breeder-friendly molecular markers can be used to improve MAS for PRR resistance.