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Identification of Molecular Markers Associated with the Rps8 locus in Soybean and Evaluation of Microsporogenesis in Rps8/rps8 Heterozygous Lines

Ortega, Maria Andrea
http://rave.ohiolink.edu/etdc/view?acc_num=osu1259772038

Abstract Details

2009, Master of Science, Ohio State University, Plant Pathology.
Phytophthora root and stem rot caused by Phytophthora sojae Kaufm. & Gerd. is one of the most damaging diseases of soybean, with an estimated worldwide loss of revenue of $1-2 billion per year. Management is principally done by planting cultivars with resistance. Monogenic race specific resistance genes to P. sojae (Rps) confer resistance to pathogen strains carrying the virulence gene (Avr). The durability of a deployed gene in the field is limited by generation of new virulence pathotypes of P. sojae that can evade the Rps-mediated immunity. Rps8 was identified in the South Korean landrace PI 399073 and to facilitate its introduction in commercial cultivars, molecular markers closely linked with the locus are required. These markers can also assist in the cloning of this gene, allowing us to enrich the knowledge on: the genomic organization and structure of Rps genes and the study of soybean-P. sojae race specific interactions. In this study, resistance to P. sojae was evaluated on eight Williams (rps8/rps8) x PI 399073 (Rps8/Rps8) populations, and one PI 399073 (Rps8/Rps8) x PI 408211B (multiple Rps genes) population. In the Williams x PI 399073 crosses, phenotypic ratios were highly skewed with an excess of Rps8/Rps8 lines, maintenance of heterozygosity and few rps8/rps8 lines. A graphical genotype was generated from three Williams x PI 399073 BC4F2:3 populations as Rps8 was associated with a 2.23 Mbp region on chromosome 13. The linkage of this region with Rps8 was confirmed in BC4F4:5 generation. In a PI 399073 x PI 408211B F4:5 a different locus which conferred resistance to P. sojae isolate Butmu was identified adjacent to Rps8. This locus segregates as a single dominant gene and this region in this population was segregating in a Mendalian fashion. Male gametogenesis was evaluated in the parental genotypes and heterozygous lines at the Rps8 region. In the parent, PI 399073, a mix of abnormal meiotic products was observed. In selected heterozygous lines from one of the populations with segregation distortion, meiotic abnormalities as well as DNA in microcytes were observed. To summarize, in PI 399073, resistance to P. sojae on chromosome 13 could be comprised of more than one Rps gene and sequencing of this region will be crucial to elucidate its complexity. Markers linked with the two resistance loci can be used for the screening of breeding lines. Meiotic abnormalities may have contributed to the segregation distortion of Rps8 in the Williams x PI 399073 populations, however, further studies would be required to determine the meiotic fate of this genomic region.
Anne Dorrance, PhD (Advisor)
Esther van der Knaap, PhD (Committee Member)
Guo-Liang Wang, PhD (Committee Member)
150 p.
Plant Pathology
Soybean; Phytophthora sojae; stem and root rot; chromosome 13; segregation distortion; microsporogenesis; microcytes; molecular mapping; graphical genotype; ssr genotyping; snp genotyping; marker assisted selection; disease resistance; oomycete; r genes

Recommended Citations

Citations

  • Ortega, M. A. (2009). Identification of Molecular Markers Associated with the Rps8 locus in Soybean and Evaluation of Microsporogenesis in Rps8/rps8 Heterozygous Lines [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259772038

    APA Style (7th edition)

  • Ortega, Maria. Identification of Molecular Markers Associated with the Rps8 locus in Soybean and Evaluation of Microsporogenesis in Rps8/rps8 Heterozygous Lines. 2009. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1259772038.

    MLA Style (8th edition)

  • Ortega, Maria. "Identification of Molecular Markers Associated with the Rps8 locus in Soybean and Evaluation of Microsporogenesis in Rps8/rps8 Heterozygous Lines." Master's thesis, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259772038

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.