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Study of incomplete resistance to Phytophthora sojae in soybean

Mora, Santiago Xavier Mideros
http://rave.ohiolink.edu/etdc/view?acc_num=osu1407404366

Abstract Details

2006, Master of Science, Ohio State University, Plant Pathology.
Phytophthora root and stem rot caused by Phytophthora sojae, is a serious limitation to soybean production in the United States. Extensive deployment of Rps genes in soybean cultivars has led to adaptations in the P. sojae populations. Partial resistance to P. sojae in soybeans is effective against all races of the pathogen and is a form of incomplete resistance where the plant reduces the rate of colonization of the pathogen. In addition to partial resistance other types of incomplete resistance have also been described. Rps2 is a single dominant gene that confers incomplete resistance in soybean hypocotyls. Root resistance, thought to be quantitatively inherited, is another form of race specific resistance that appears to function only in the roots. In order to differentiate partial resistance from the other types of incomplete resistance that are race specific, components of resistance were analyzed and the cytology of infection compared. For this study attempts to genetically transform P. sojae to express a marker gene were unsuccessful. Three components were measured (lesion length, oospore production and infection frequency) in 8 soybean genotypes that were inoculated with non-transformed P. sojae isolates on the roots. Light and epifluorescent microscopy were used to study transversal cuts of Trypan blue stained root samples that were also inoculated with P. sojae. Soybean partial resistance was found to be composed of various components that interact to produce the partial resistance phenotype for defense against P. sojae in the roots. It was also found that the Rps2 and root resistant genotypes had significantly reduced levels for all of the components of resistance studied in comparison to the partially resistant genotype Conrad. However, the high levels of partial resistance in Jack were indistinguishable from the Rps2 reaction for all the components studied. In the cytology study it was found that P. sojae penetrates into all the soybean incomplete resistant genotypes: partial resistant, Rps2, and root resistant. Several mechanisms of resistance were observed: i) the resistance phenotype (Rps1a) contained the pathogen biotrophic growth from between 0 to 24 hai in a hypersensitive response; ii) Rps2 and root resistance phenotypes, also stopped growth of the pathogen but this occurred between 24 and 48 hai in a delayed hypersensitive response and iii) the partial resistance and the susceptible phenotypes allowed biotrophic colonization of P. sojae. Finally a methodology to differentiate among mechanisms of incomplete resistance to P. sojae in soybean was identified based on the number of dead cells and extent of colonization that differed in partial resistance and Rps2 phenotypes.
Anne E. Dorrance (Advisor)
Sophien Kamoun (Committee Member)
Clay H. Sneller (Committee Member)
126 p.
Plant Pathology

Recommended Citations

Citations

  • Mora, S. X. M. (2006). Study of incomplete resistance to Phytophthora sojae in soybean [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407404366

    APA Style (7th edition)

  • Mora, Santiago. Study of incomplete resistance to Phytophthora sojae in soybean. 2006. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1407404366.

    MLA Style (8th edition)

  • Mora, Santiago. "Study of incomplete resistance to Phytophthora sojae in soybean." Master's thesis, Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407404366

    Chicago Manual of Style (17th edition)

osu1407404366
323
© 2006, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.